Lessons

Every lesson on Hone, in teaching order

1473 short lessons across 21 tracks. Each one is an idea in plain words, what it is for, how to think about it, a worked example that runs, and the trap.

Hone is a place to practise a subject or a career: you answer questions, solve problems, and it remembers what you got wrong so it can ask you again later. These are the written explanations behind that, free to read on their own. A track is one subject or one career, like Python, the command line, or the electrical trade. A topic is one idea inside it.

Python 102 lessons

Python quick reference: every topic on one page, one line each.

Your first code · Values and names

Storing a value in a name storing a value in a name
Text that looks like a number is still text text vs numbers
Turning a value into text turning a value into text
Text that should have been a number text that should be a number
Notes to the next reader, who is usually you comments (# notes)

Your first code · Doing things

Functions hand something back calling a function
Showing a value versus giving it back showing a value or handing it back
How long is this text how long is this text
One case to compare in one case to compare in
Cleaning and reshaping text cleaning and reshaping text

Your first code · Numbers that behave

The remainder % the remainder
Whole parts and what is left over whole parts and remainders (// and %)
Whole-number division // whole-number division
Raising to a power ** raising to a power
Which operator goes first which operator goes first

Keep the edge · Money and time

Money is whole cents money is whole cents
A time that knows where it is a time that knows its timezone
Rounding halves to even round() sends halves to even
Do not compare floats with == do not compare decimals with ==

Keep the edge · Data at scale

Deduplicating records deduplicating records
Sort by two things stable sorting
When a join multiplies rows when a join multiplies rows
Rows with no key vanish from a group-by rows with no key vanish from a group-by
A comprehension keeps its variable to itself comprehension variables

Data structures and algorithms · Things in a line

Nodes that point at the next node linked lists
Last in first out, and first in first out stacks and queues
Two fingers, one pass two pointers
A window that grows and shrinks the sliding window

Data structures and algorithms · Things in a grid

A grid is a list of lists grids (a list of lists)

Data structures and algorithms · Things in a tree

A node, a left and a right binary trees
Two ways to visit every node walking a tree

Data structures and algorithms · Things in an order

What sorting costs, and what it buys what sorting costs
Always hand me the smallest heaps (the smallest first)

Data structures and algorithms · Things joined to things

Things joined to things graphs (things joined to things)
Remember what you already worked out memoising (not doing it twice)
Take the best step now, and never look back greedy choices

Asking a question of every item at once any() and all()
Walking a dict: keys, values, or both looping over a dict
Putting values into text putting values into text
Leave as soon as you know leave as soon as you know
Sorting in place versus sorting a copy sort() vs sorted()
From pieces to one string join (pieces to text)
Walking two lists together zip (walk two lists)

JavaScript 75 lessons

JavaScript quick reference: every topic on one page, one line each.

Data structures and algorithms · Things in a line

Objects that point at the next object linked lists
Last in first out, and first in first out stacks and queues
Two fingers, one pass two pointers
A window that grows and shrinks the sliding window

Data structures and algorithms · Things in a grid

A grid is an array of arrays grids (an array of arrays)
A loop inside a loop multiplies loop inside a loop
One pass, one running fact scanning an array is slow

Data structures and algorithms · Things in a tree

A node, a left and a right binary trees
Two ways to visit every node walking a tree
A problem defined by a smaller version of itself a function that calls itself

Data structures and algorithms · Things in an order

What sorting costs, and what it buys what sorting costs
Always hand me the smallest heaps (the smallest first)
Sort by the thing that matters sort with a comparator

Data structures and algorithms · Things joined to things

Things joined to things graphs (things joined to things)
Remember what you already worked out memoising (not doing it twice)
Take the best step now, and never look back greedy choices

JavaScript for the web · Values

What kind of value is this typeof
When + stops adding + with a string and a number
Joining text joining two strings
Plain addition adding two numbers
Flipping a condition ! flips true and false
A one-line if that has a value the one-line if

JavaScript for the web · Arrays

Adding to the end push
Picking an item by position the first item is item 0
How many length and the last item
Keeping what passes filter
Gluing a list into text join (pieces to text)
slice copies, splice cuts slice copies, splice changes

JavaScript for the web · Truth and equality

What counts as true what counts as true
Why === and not == why === and not ==
Does it have a value null vs undefined vs empty
Two kinds of nothing never set, or set to nothing
Forcing a boolean !! makes a boolean
A default only for missing ?? only catches null and undefined

JavaScript for the web · Functions and scope

Where a variable lives let is bounded by its block
What exists before its line reading a name before it exists
A function that remembers where it was made functions that remember
Arrows keep the this they were born in arrow functions and this
A default when the argument is missing default parameters
Copying with three dots ... spread

JavaScript for the web · Async

An async function always returns a promise async always hands back a promise
Catching a rejection catching a promise
await pauses only its own function async / await
What runs when the event loop

JavaScript for the web · Objects and classes

A class builds objects with new classes and new
this is the object before the dot this in methods
extends shares a parent; super reaches it extends and super
Getters read like properties; static lives on the class getters, static and #private
A class is a prototype with nicer syntax prototypes under the hood

JavaScript for the web · Prove it works

assert says what must be true assert
A test is a named function that asserts one fact a test function
Arrange, act, assert arrange, act, assert
Test the ends first: nothing, one, everything the same edge cases first

Asking a question of every item at once some() and every()
Naming a value storing a value in a name
Build a new array from an old one map and filter
const fixes the name, not the contents reassigning a const
Putting values into text template literals
Remember what you have seen, in a Map look it up in a Map
Is it in there? is it in there
Whole parts and remainders in JavaScript whole parts and remainders (Math.floor and %)
Array or object? array or Map?
Changing what was handed to you copy before you change it
Object keys are strings object keys are text
Counting with a loop counting loops
Fold a list into one value folding a list into one value
Leave as soon as you know leave as soon as you know
A collection that refuses duplicates Set removes duplicates
A window onto an array or string slice()
sort() sorts as text sorting numbers as text
Halve the search space each step searching sorted data
Spend memory to save time memory for speed
Cleaning and reshaping text cleaning and reshaping text
Repeat until something changes while loops
Walking two arrays together zip (walk two lists)

TypeScript 107 lessons

TypeScript quick reference: every topic on one page, one line each.

Data structures and algorithms · Things in a line

Objects that point at the next object linked lists
Last in first out, and first in first out stacks and queues
Two fingers, one pass two pointers
A window that grows and shrinks the sliding window

Data structures and algorithms · Things in a grid

A grid is an array of arrays grids (an array of arrays)
A loop inside a loop multiplies loop inside a loop
One pass, one running fact scanning an array is slow

Data structures and algorithms · Things in a tree

A node, a left and a right binary trees
Two ways to visit every node walking a tree
A problem defined by a smaller version of itself a function that calls itself

Data structures and algorithms · Things in an order

What sorting costs, and what it buys what sorting costs
Always hand me the smallest heaps (the smallest first)
Sort by the thing that matters sort with a comparator

Data structures and algorithms · Things joined to things

Things joined to things graphs (things joined to things)
Remember what you already worked out memoising (not doing it twice)
Take the best step now, and never look back greedy choices

TypeScript, properly · Why types

Types, checked before it runs what TypeScript adds
Saying what a thing is type annotations
Types you did not write inference
Types are gone at runtime types are gone at runtime
any turns the checker off any turns the checking off

TypeScript, properly · Shapes

The shape of an object interfaces and optional fields
A property that may be missing a property that may not be there
One of several types union types
Exactly these strings a type of exact values
A fixed shape of array a fixed-length, fixed-type array

TypeScript, properly · Narrowing

Checks the compiler follows narrowing with checks
A check the compiler remembers teaching the compiler what it is
Nothing has a type too strict null checks
Anything in, nothing out until checked unknown makes you check first
null is not a string null is not every type's member

TypeScript, properly · Generics and beyond

A function that keeps the type it was given generics
A generic with a requirement extends: what a generic must have
The keys as a type keyof: the names of the keys
A tag that tells the variants apart discriminated unions
Every case, or a compile error never: proving you covered every case

TypeScript, properly · Classes and interfaces

Fields are declared with their types typed fields and parameter properties
private, protected and readonly draw the fence private, protected, readonly
An interface describes; a class implements and builds implements an interface
An abstract class shares real code and demands the rest abstract classes
extends with super first, a compatible override, and instanceof narrowing extends, override, instanceof

TypeScript, properly · Prove it works

Types promise a shape; a test proves a value types promise, tests prove
A typed test is checked before it runs a typed test
Arrange, act, assert, with the fixture typed arrange, act, assert, typed
The type names the edge; the test proves it the type names the edge

Asking a question of every item at once some() and every()
Naming a value storing a value in a name
An async function always returns a promise async always hands back a promise
A function that remembers where it was made functions that remember
Build a new array from an old one map and filter
const fixes the name, not the contents reassigning a const
Putting values into text template literals
Remember what you have seen, in a Map look it up in a Map
What exists before its line reading a name before it exists
Is it in there? is it in there
Whole parts and remainders in JavaScript whole parts and remainders (Math.floor and %)
Plain addition adding two numbers
Arrange, act, assert arrange, act, assert
Picking an item by position the first item is item 0
Adding to the end push
Arrows keep the this they were born in arrow functions and this
assert says what must be true assert
await pauses only its own function async / await
A class builds objects with new classes and new
Joining text joining two strings
A default when the argument is missing default parameters
Forcing a boolean !! makes a boolean
Test the ends first: nothing, one, everything the same edge cases first
Why === and not == why === and not ==
What runs when the event loop
extends shares a parent; super reaches it extends and super
Keeping what passes filter
Getters read like properties; static lives on the class getters, static and #private
Gluing a list into text join (pieces to text)
How many length and the last item
Flipping a condition ! flips true and false
Does it have a value null vs undefined vs empty
A default only for missing ?? only catches null and undefined
Catching a rejection catching a promise
A class is a prototype with nicer syntax prototypes under the hood
Copying with three dots ... spread
When + stops adding + with a string and a number
A one-line if that has a value the one-line if
A test is a named function that asserts one fact a test function
this is the object before the dot this in methods
What kind of value is this typeof
Where a variable lives let is bounded by its block
Array or object? array or Map?
Changing what was handed to you copy before you change it
Two kinds of nothing never set, or set to nothing
Object keys are strings object keys are text
Counting with a loop counting loops
Fold a list into one value folding a list into one value
Leave as soon as you know leave as soon as you know
A collection that refuses duplicates Set removes duplicates
slice copies, splice cuts slice copies, splice changes
A window onto an array or string slice()
sort() sorts as text sorting numbers as text
Halve the search space each step searching sorted data
Spend memory to save time memory for speed
Cleaning and reshaping text cleaning and reshaping text
What counts as true what counts as true
any switches checking off; unknown makes you prove it any vs unknown
Promise not to change it readonly
Check the shape, keep the detail satisfies
Repeat until something changes while loops
Walking two arrays together zip (walk two lists)

SQL 52 lessons

SQL quick reference: every topic on one page, one line each.

Queries that hold up · It ran, and it lied

Where the filter goes in a LEFT JOIN a WHERE that undoes a LEFT JOIN
Two totals from one pass adding up only some rows
Arithmetic on dates date ranges
A range, inclusive BETWEEN is inclusive
AND binds tighter than OR AND before OR

Queries that hold up · Filter at the right moment

Filter rows with WHERE, groups with HAVING HAVING vs WHERE
What SELECT may contain after GROUP BY grouped SELECTs
Sorting by more than one thing ORDER BY two columns
Just some of the rows LIMIT

Queries that hold up · A question inside a question

A query inside a query subqueries
A query that returns one value comparing against one computed value
Is there such a row is there at least one

Queries that hold up · One row per thing, and what it costs

The whole row that holds the maximum the top row per group
A subquery that runs per row a subquery that runs per row
DISTINCT collapses duplicates why DISTINCT is slow

Queries that hold up · Changing data without regret

UPDATE needs a WHERE UPDATE needs WHERE
DELETE needs a WHERE DELETE needs WHERE
Ranking with window functions transactions
Adding a row INSERT

SQL for the workplace · Ask a question

Asking a table for columns SELECT basics
Keeping only the rows you mean WHERE
Both conditions at once AND narrows the rows
The top of a sorted list the top one, by order
Each value once one row per value
Pattern matching on text LIKE

SQL for the workplace · Count and sum

One number from many rows COUNT, SUM, AVG
How many rows counting rows
Adding a column up adding a column up
The largest value the largest value
One number per group GROUP BY
Bucketing by a computed value GROUP BY an expression
Filtering groups filtering the groups, not the rows
Averages skip the blanks AVG skips the NULLs

SQL for the workplace · Join the tables

Rows from two tables, matched up JOIN
Only the matches INNER JOIN
Keep every row on the left keeping the rows with no match
Keep everyone, spot the gaps LEFT JOIN and NULL
When a join multiplies rows when a join multiplies rows
An inner join drops the unmatched an inner join loses rows

SQL for the workplace · Nothing is something

NULL means unknown what NULL means
Finding the blanks testing for NULL
A value instead of NULL COALESCE
Why = NULL finds nothing comparing with NULL
NOT IN and a single NULL NOT IN meets a NULL
COUNT(*) versus COUNT(column) COUNT and NULL

SQL for the workplace · The real reports

Naming a step naming a query with WITH
Turning values into labels sorting rows into buckets
Grouping by calendar month grouping by month across years
The latest row per group the most recent one each
A total beside every row a window keeps every row
A running total a total that grows down the rows

Naming a column or table aliases (AS)

Regex 52 lessons

Regex quick reference: every topic on one page, one line each.

Regex that reads · Literal to pattern

Characters match themselves literal characters
Any one character any one character
Literal special characters escaping specials
One character from a set character classes
Matching a digit \d: any digit

Regex that reads · How many

How many times + * ? quantifiers
One or more +: one or more
Zero or more *: none or more
Zero or one ?: there or not
Exactly, at least, between {2,4}: between two counts

Regex that reads · Where

Pin the pattern to the edges ^ and $ anchors
The edge of a word word boundaries
This or that alternation (or)
Capturing the parts capture groups
Capturing a piece ( ): keeping the part you matched

Regex that reads · The sharp edges

Greedy takes all it can greedy vs lazy
As little as possible *?: stopping at the first match
Check what follows without taking it lookahead
The same thing again backreferences
Patterns that never finish catastrophic backtracking

The pattern that is right about your data · Which call, and what it hands back

Where the engine starts looking search or match: where it starts looking
All of it, or nothing fullmatch: all of it or nothing
The matches, and where they were finditer: matches and where they were
Nothing is None, not empty a failed search hands back None
Zero is the whole match group(0): the whole match
findall hands back the group findall hands back the group, not the match

The pattern that is right about your data · Change the text, not just find it

Putting the pieces back in a different order \1 in the replacement
A replacement that decides replacing with a function
Only the first few, and how many there were replacing only the first few
Splitting, and keeping what you split on split: keeping the separator

The pattern that is right about your data · A flag changes the whole meaning

One start, or one per line ^ and $: once, or once per line
The dot stops at a newline the dot stops at a newline
A pattern with room to breathe VERBOSE: a pattern with room to breathe
A flag written inside the pattern (?i): a flag inside the pattern
Two different ends $ and \Z: two different ends

The pattern that is right about your data · The data is not ASCII

A letter is not always a-z \w is not only English
More digits than you think \d is more digits than you think
Narrowing it back to ASCII ASCII: back to a-z and 0-9
Bytes are not text matching bytes rather than text

The pattern that is right about your data · Fast, or hanging

A quantifier inside a quantifier a quantifier inside a quantifier
Telling the engine where to start anchoring so it gives up early
Compiling, and what it is really for the pattern cache, and when it stops helping
The first branch that works, wins which alternative wins

The pattern that is right about your data · When not to reach for one

HTML nests and a pattern cannot count why not to parse HTML with one
The comma inside the quotes the comma inside the quotes
An address you validate by sending to it an address you validate by sending to it
It can find them; it cannot pair them a pattern cannot count brackets

The pattern that is right about your data · Prove the pattern

Test it on what nearly matches testing it on what nearly matches
A match that is not the whole value a match that is not the whole value
What a person typed is not a pattern re.escape: anything a person typed
The pattern you will have to read again the pattern you will have to read again

Switches on the whole pattern flags: i, m, s and x

Git 62 lessons

Git quick reference: every topic on one page, one line each. Run these for real: a repository in this page that you cannot break.

Git without fear · The three areas

Starting a repository starting a repository
What Git thinks right now what git can see right now
Choosing what the next commit contains choosing what goes in the commit
Recording a snapshot recording a snapshot
Working tree, index, repository the folder, the staging area, the last commit
Reading the history reading the history

Git without fear · The daily rhythm

Seeing the change before you record it what changed, line by line
A message someone can use writing a commit message
Files Git should never track files git should not watch
Where HEAD points HEAD: where you are standing
Taking a change back putting a file back
Removing a file properly deleting a file git tracks
Renaming so history follows renaming a tracked file
Fixing the last commit redoing the last commit

Git without fear · Branches and merges

A branch is a pointer a branch is a name for a commit
Moving between branches moving between branches
Bringing a branch in fast-forward: no merge needed
When both sides moved when both sides moved
Resolving a conflict when git will not guess
Shelving work for a moment stash: putting work aside

Git without fear · Working with others

Getting a copy of a project copying a whole repository
Named places to sync with the other end, by name
fetch looks, pull changes fetch, then merge
Sending commits up sending your commits
Proposing a change asking somebody to merge it
Marking a release naming a commit for good

Git without fear · Undo, safely

Which undo which undo, and when
Undo by adding undoing by adding a commit
Moving the branch back moving the branch back
Replaying your commits on a new base replaying commits somewhere else
Taking one commit taking one commit from another branch
Looking around without a branch committing with no branch attached
Who changed this line, and why who last changed this line

When git goes wrong · Before you type anything

Look before you touch what to do before you touch anything
Everywhere HEAD has been everywhere HEAD has been
Three questions, three commands three commands that tell you where you are
Unreachable is not deleted unreachable is not deleted
Wrong files, or wrong history is it the tree or the history

When git goes wrong · Work you have not committed

One file back to how it was putting one back, not the lot
Taking it out of the next commit taking it out of the next commit
Removing files git never knew about clearing out what was never tracked
Getting a stash back getting a stash back
Back to the branch you were on returning to the previous branch

When git goes wrong · Work you have committed

Undoing a commit and keeping the work undoing a commit, keeping the work
Soft, mixed and hard soft, mixed and hard
Rewriting history, or recording an undo rewriting history or recording an undo
Amend replaces, it does not edit amend replaces, it does not edit
The commit went on the wrong branch the commit went on the wrong branch

When git goes wrong · The history moved under you

What force does to everybody else what force does to everybody else
Merge or replay, when you pull merge or replay when you pull
Both sides have moved both sides have moved
Getting a lost commit back getting a lost commit back
The branch it tracked is gone the branch it tracked is gone

When git goes wrong · A merge that stopped half way

Reading a conflict reading a conflict
The free way out the free way out of a merge or rebase
Stop, resolve, continue the stop-resolve-continue loop
Knowing you have finished knowing you have finished resolving

When git goes wrong · So the next one is smaller

Small commits are cheap to undo small commits are cheap to undo
A branch before anything risky a branch before anything risky
A commit is a save, a push is a backup a commit is a save, a push is a backup
Marking the known-good point marking the known-good point
The short list git cannot get back the short list git cannot get back

Terminal 52 lessons

Terminal quick reference: every topic on one page, one line each. Run these for real: a terminal in this page that you cannot break.

The terminal, without fear · Where am I

Where am I? where am I
What is here? what is in here
Moving around moving between folders
. is here, .. is up this folder and the one above (. and ..)
~ is home ~ (home)

The terminal, without fear · Files and folders

Making folders making a folder
Making an empty file making an empty file
Copying copying a file
Moving and renaming are one command moving and renaming
Deleting, for good deleting, with no undo

The terminal, without fear · Look inside

Reading a file cat: print it to the screen
The start and the end of a file head and tail
Counting lines counting lines and words
Finding lines finding the lines that match
Finding files by name finding files by name

The terminal, without fear · Plumbing

The pipe the pipe |
Sending output to a file > (save output)
Adding to a file >> (add to the end)
Two streams: output and errors 2> (errors)
Then, or else, regardless if it worked, if it failed (&& and ||)

The terminal, without fear · Make it yours

Variables, and export variables and export
Every command reports success or failure $? (exit status)
Permissions, and making a script runnable making a file runnable
Using a command's output inside another $(...) (a command's output)
A script: commands in a file, run as one a script with a shebang

Get the answer out of the file · What a pipe really is

What a pipe actually carries what a pipe carries
Each stage sees only the one before each stage sees only the one before
Errors do not go down the pipe errors do not go down the pipe
Build it one stage at a time build a pipeline one stage at a time

Get the answer out of the file · Find the lines you want

grep -c counts lines, not matches grep -c counts lines, not matches
Everything except grep -v: everything but
Whole words only grep -w: whole words only
However it was typed grep -i: however it was typed
Somewhere to go back to grep -n: somewhere to go back to

Get the answer out of the file · Take the column you need

Taking one column cut -d and -f
The delimiter you did not name cut's delimiter is a tab
When the columns are spaces runs of spaces are not fields

Get the answer out of the file · Put it in an order that means something

sort compares text until you tell it otherwise sort -n: 9 before 100
Sorting on a column sort -k: on which column
The distinct values sort -u: the distinct values

Get the answer out of the file · Count what repeats

uniq only sees its neighbour uniq only sees neighbours
How many of each uniq -c: how many of each
The ten commonest values the ten commonest values
wc counts newlines wc -l counts newlines

Get the answer out of the file · When the answer looks wrong

Nothing is an answer when a pipeline prints nothing
How many rows, how many things how many rows, how many things
Two different stars the shell's * and grep's *
A space in a variable splits it a space in a variable splits it

Get the answer out of the file · On a file too big to open

head stops the pipeline head stops a pipeline early
Get it right on a thousand lines get it right on a thousand lines
A pipeline's exit code is the last stage's a pipeline's code is the last stage's
The one that worked, written down the one that worked, written down

HTML and CSS 54 lessons

HTML and CSS quick reference: every topic on one page, one line each.

Your first web page · The page

The page skeleton the page skeleton
Tags, elements, content tags and elements
Headings headings
Paragraphs and whitespace paragraphs
Links links

Your first web page · More than text

Images and alt text images and alt
Lists lists
Attributes attributes
Forms forms
Semantic tags semantic tags

Your first web page · Give it style

A CSS rule a CSS rule
Selectors selectors
Attaching CSS attaching CSS
Colour and background colour and background
Fonts and sizes fonts and sizes

Your first web page · The box

The box model the box model
box-sizing box-sizing
px, rem, em and % px, rem, em and %
display display
The cascade the cascade

Your first web page · Layout that holds

Flexbox flexbox
Grid grid
position position
Media queries media queries
:hover and :focus :hover and :focus

The page everyone can use · Who cannot use this page

Who a page can shut out who a page can shut out
Role, name and state role, name and state
Put the mouse down and Tab put the mouse down and Tab
Cheapest while you are writing it cheapest while you are writing it

The page everyone can use · The label that is not attached

for= and id=, or wrap it for= and id=, or wrap it
A field that announces nothing a field that announces nothing
A placeholder is not a label a placeholder is not a label
Naming a group of controls naming a group of controls

The page everyone can use · The button that is a div

A button, not a styled div a button, not a styled div
A role does not make it reachable a role does not make it reachable
Goes somewhere, or does something goes somewhere, or does something
0, -1, and never a positive one 0, -1, and never a positive one

The page everyone can use · Where the focus went

The keyboard user's cursor the keyboard user's cursor
:focus-visible, and a ring you can see :focus-visible, and a ring you can see
The HTML decides, not the CSS the HTML decides, not the CSS
Past the navigation, every page past the navigation, every page

The page everyone can use · Colour you can actually read

What a contrast ratio measures what a contrast ratio measures
4.5 for text, 3 for the rest 4.5 for text, 3 for the rest
Colour is never the only signal colour is never the only signal
A dark theme is all new pairs a dark theme is all new pairs

The page everyone can use · Pictures, and what they are for

What the image is for here what the image is for here
alt= on purpose alt= on purpose
No alt at all no alt at all
Not "image of" not "image of"

The page everyone can use · The shape of the page

Headings are the outline headings are the outline
One h1: what this page is one h1: what this page is
Regions you can jump to regions you can jump to
Which language to pronounce which language to pronounce
th, and which way it runs th, and which way it runs

Industrial control 54 lessons

Industrial control quick reference: every topic on one page, one line each.

Ladder logic from zero · What a PLC is

What a PLC does what a PLC does
Inputs: how the PLC senses an input: what the PLC can see
Outputs: how the PLC acts an output: what the PLC drives
One line of a ladder rungs
The two rails the two rails a rung sits between
Left to right, top to bottom reading a ladder, rung by rung

Ladder logic from zero · Contacts and coils

Normally open: passes power when TRUE normally open contact
Normally closed: passes power when FALSE normally closed contact
The coil is the action the coil at the end of a rung
Series is AND contacts in series are AND
Parallel is OR contacts in parallel are OR
Top to bottom, every scan the scan cycle

Ladder logic from zero · Hold and time

Keep running after the button is released seal-in circuits
Set and reset set and reset bits
On-delay on-delay timer (TON)
The off-delay the off-delay timer
Counting edges counting events
Exactly once acting on the change, not the state

Ladder logic from zero · Do no harm

A broken wire must stop the machine fail-safe wiring
Wired to fail safe wiring an emergency stop
One coil, two rungs, one winner the double coil trap
Never both at once two outputs that can never run together
Sequences and the timer that watches the watchdog
The PLC is not the safety system safety is not the PLC

Why the machine stopped · Before you touch anything

What changed what changed
What one scan really does what one scan really does
Finding the rung that stopped finding the rung that stopped
Watching it run versus reading it watching it run versus reading it

Why the machine stopped · The coil written twice

The coil written on two rungs the coil written on two rungs
Finding a second writer finding a second writer
One coil, one rung one coil, one rung

Why the machine stopped · Rung order

Rung 2 sees what rung 1 wrote rung 2 sees what rung 1 wrote
Logic that is one scan behind logic that is one scan behind
Moving a rung is a change moving a rung is a change

Why the machine stopped · The seal-in

How a seal-in holds how a seal-in holds
Where the stop belongs where the stop belongs
An output that will not drop out an output that will not drop out
Hold-to-run, on purpose hold-to-run, on purpose

Why the machine stopped · Latches that stick

A latch remembers, a coil does not a latch remembers, a coil does not
The reset that can never run the reset that can never run
Set and reset in the same scan set and reset in the same scan
Latch, seal-in, or plain coil latch, seal-in, or plain coil

Why the machine stopped · Timers that never finish

A timer adds up time a timer adds up time
One false scan throws it away one false scan throws it away
Done is not remembered done is not remembered
An input that will not stay still an input that will not stay still

Why the machine stopped · The contact that must be normally closed

A healthy stop button reads 1 a healthy stop button reads 1
Closed in the field, open in the rung closed in the field, open in the rung
What a broken wire does what a broken wire does
Silence is a fault silence is a fault
When both directions are called at once when both directions are called at once

What the screen shows HMI tags
True for exactly one scan one-shots
Outputs update at the end of the scan when outputs update

Network switches 95 lessons

Network switches quick reference: every topic on one page, one line each. Run these for real: a terminal in this page that you cannot break.

Run a switch, start to finish · Get to the prompt

What a switch is actually doing what a switch does
Getting a screen on it console access
Three rooms, and the door between them the mode stack
The prompt is telling you where you are reading the prompt
The switch will tell you what it accepts ? asks the switch
Type less, and know exactly when you cannot abbreviating commands

Run a switch, start to finish · Make the switch yours

Name the box naming the switch
Label the port port descriptions
The configuration is a document you can read the running config
Running is not saved saving the configuration
Keep a copy where the switch is not backing it up
A password on the way in the enable secret

Run a switch, start to finish · Split it into VLANs

One switch, several networks what a VLAN is
What a VLAN actually separates broadcast domains
Making a VLAN creating a VLAN
Putting a port in a VLAN access ports
Reading the VLAN table reading the VLAN table
The VLAN that made itself the VLAN that made itself
The desk that cannot see the server a port in the wrong VLAN

Run a switch, start to finish · Reach it over the network

A switch does not have an IP address, a VLAN does the management interface
Giving it an address the management address
Reaching it from another subnet the default gateway
A port that is administratively down shut and no shut
The four things that make a switch reachable making it reachable
Telnet sends your password across the network in the clear SSH instead of telnet

Run a switch, start to finish · Carry VLANs between switches

One cable, every VLAN trunks
The four bytes that carry the VLAN 802.1Q tagging
1 to 4094, and not 4096 the 1 to 4094 range
VLAN 1 is not a good place to live VLAN 1
The one VLAN on a trunk that goes untagged the native VLAN
Let across only what belongs the allowed VLAN list
Two switches disagreeing, quietly a native VLAN mismatch
The trunk that is not trunking a trunk that is not trunking

Run a switch, start to finish · Keep it up and keep it safe

What the switch has learned the MAC address table
What it does when it has not learned yet flooding the unknown
Thirty seconds of nothing, on every desk portfast
The port that must never see another switch BPDU guard
One address per desk port security
Reading a switch you did not configure auditing a switch

Run a switch, start to finish · Look after the software

The switch has a disk, and it can fill up the switch's flash
What the .bin file actually is the software image
Telling it which image to boot which image it boots
An upgrade, in the order the steps depend on each other upgrading the software
Restarting, and what that costs reloading
A copy of the configuration that is not on the switch backing up to a server
Back to how it came out of the box erasing the configuration
Getting back into a switch nobody has the password for password recovery

Run a switch, start to finish · On the plant floor

Allen-Bradley Stratix, and why Cisco knowledge carries over Allen-Bradley Stratix
EtherNet/IP is ordinary Ethernet EtherNet/IP
Designing VLANs for a production cell VLANs for a cell
Multicast, and the switch that knows who asked IGMP snooping
Why the plant floor is wired in a ring industrial ring topologies
A phone and a PC on one socket voice VLANs
The link that works badly rather than failing duplex and speed
Power down the same cable power over Ethernet
Why the link between buildings is fibre fibre links

Replace a switch without breaking anything · Before the box comes out

The one thing that has to exist before the box comes out why a switch gets replaced
The serial nobody can reconstruct later the part number and the serial
What every port was doing, before you unplug it what every port was doing
What is on the other end of the cable what is on the other end
The old switch is the rollback being able to go back

Replace a switch without breaking anything · What a backup does and does not carry

copy FROM TO, and there are no exceptions copy, source first
A backup you have not read is a filename a backup you have read
What a backup leaves behind what a backup leaves behind
The VLAN database is not part of the configuration VLANs live outside the config
Server, client, transparent server, client, transparent
The secrets that travel, and the one that does not the secrets that do not travel

Replace a switch without breaking anything · Putting it on the new one

Check, restore, verify, then save the order a restore goes in
The lines that did not take the lines that did not take
A configuration that does not fit the box a config that does not fit the box
Two boxes, one address two boxes, one address
Putting the VLAN names back putting the VLAN names back

Replace a switch without breaking anything · Proving it works

Check the VLANs, because they are what is missing checking the VLANs came out right
Line by line against the paper checking every port came back
The console cannot prove remote access checking you can still get in
Save last, and mean it saving it, last
Two files, in two places wiping the one that is leaving

Replace a switch without breaking anything · In a corporate closet

A desk port and a machine port are configured for different lives an office closet, not a plant floor
One cable, two VLANs the phone and the PC on one port
The switch does not hand out addresses where a desk gets its address
The configuration arrives; the identity does not the port that asks who you are
The serials are the part nobody can reconstruct the ticket and the window

Replace a switch without breaking anything · Remembering any of it

copy FROM TO, with no exceptions copy FROM TO, source first
Ask the box the switch will tell you
Four questions answer almost everything the four questions at any console
do: one command somewhere else, and back looking without leaving
Filter it, and mind the capital letters finding one line in three hundred
The note is the only history a switch has what you leave for the next person

Building a switch out from nothing building one out
The switch shut the port itself err-disabled ports
What a storm looks like from the doorway spotting a loop
The table forgets on purpose MAC ageing
One address in two places a flapping address
Moving a port from one VLAN to another moving a port between VLANs
Trunk or access: the decision, not the command trunk or access

Electrical 38 lessons

Electrical quick reference: every topic on one page, one line each.

From a battery to a breaker panel · Current, voltage, resistance

What is actually moving in the wire what electricity is
Ohm's law: the one relationship everything hangs on Ohm's law
Power: how much work the circuit is doing power, in watts
Watts are a rate; the bill is watts times hours energy and the bill (kWh)
DC goes one way; AC turns around sixty times a second alternating and direct current (AC and DC)

From a battery to a breaker panel · Series and parallel

Series: one path, the resistances add series circuits
Parallel: more paths, less resistance parallel circuits
Mixed circuits: shrink the parallel part first series and parallel together
Where the volts go: in proportion to the ohms the voltage divider
One branch opens: what the others feel when one branch opens

From a battery to a breaker panel · Reading and measuring

The multimeter: four questions it can answer the multimeter
Amps are measured in the path, or around it measuring current, and the clamp meter
The nameplate tells you what to size for reading a nameplate
Two hots and a neutral: how 120 and 240 both come from one service 120/240 V in a home

From a battery to a breaker panel · Wire and protection

Wire sizes: the smaller the number, the bigger the wire wire sizes (AWG)
How much current a wire may carry how much a wire can carry
The 80 percent rule: a circuit that runs for hours is sized at 125 percent the 80 percent rule
The breaker protects the wire, not the appliance sizing a breaker
Voltage drop: the wire eats some of the volts on the way voltage drop over a run
Conduit fill: forty percent of the pipe is the most you may fill conduit fill
GFCI and AFCI: two devices for two different ways to get hurt GFCI and AFCI

From a battery to a breaker panel · Safety

Lockout, tagout: the order that keeps the power off while you are inside lockout, tagout
Test before touch: live, dead, live test before touch
Arc flash: the explosion that needs no contact arc flash
Grounding connects to the earth; bonding connects the metal together grounding and bonding
The neutral carries current; the ground carries none, until the day it matters the neutral is not a ground

From a battery to a breaker panel · On the job

Sizing a house service: count the load the standard way load calculation for a dwelling
A motor is sized from its full-load current, and the breaker is allowed to be big motor full-load current
A 240 V circuit end to end: from the nameplate to the receptacle a 240 V circuit, end to end
A dead outlet: check in the order that costs least troubleshooting a dead outlet
Reading a panel schedule: which breaker, which leg, which wire reading a panel schedule

From a battery to a breaker panel · Becoming licensed

The hours are paid work, which is the whole reason this route is open to people the others are not the hours are paid work, not tuition
Three licences, not one, and each is a separate grant three licences, not one
Who licenses you, and the places where the answer is not the state who licenses you, and the states where it is not the state
The code is national in name and local in force the code your jurisdiction actually adopted
The examination, and what it is really testing the examination, and what it is really testing
Moving, and the paper reciprocity does not waive moving, and the paper reciprocity does not waive
The renewal clock, and why it follows the code rather than the calendar the renewal clock, and why it follows the code

Accounting 136 lessons

Accounting quick reference: every topic on one page, one line each.

From the first entry to a set of statements · The equation

The one equation the whole of accounting sits on the accounting equation
Assets, liabilities, equity: the three words in plain English assets, liabilities and equity in plain words
Every transaction touches at least two accounts every transaction has two sides
The five kinds of account the five kinds of account
Normal balance: the side each account expects to live on normal balances

From the first entry to a set of statements · Debits and credits

Debit means left. Credit means right. That is all. debit is left, credit is right
Which side makes it bigger which side makes an account bigger
The journal entry: date, debit, credit, and a line of why the journal entry
Posting: from the journal to the ledger posting to the ledger
The trial balance: what it proves, and what it cannot the trial balance

From the first entry to a set of statements · Everyday entries

A cash sale a cash sale
A sale on credit: the receivable a sale on credit and the receivable
Buying on account: the payable buying on account and the payable
Paying what you owe paying a payable
The owner puts money in the owner puts money in
Recording an expense recording an expense
The bank reconciliation, in steps the bank reconciliation

From the first entry to a set of statements · Adjusting and closing

Accrual versus cash: when does it count? accrual versus cash
Prepaid expenses: paid now, used later prepaid expenses
Unearned revenue: paid before you have earned it unearned revenue
Accrued wages: worked, not yet paid accrued wages
Straight-line depreciation straight-line depreciation
Closing the books: revenue and expenses go to equity closing the books

From the first entry to a set of statements · The statements

The income statement: what you earned and what it cost the income statement
The balance sheet: what you have and what you owe, on one day the balance sheet
How the statements tie together through equity how the statements tie through equity
Cash flow in three buckets cash flow in three buckets
Gross margin and net margin gross margin and net margin
Three ratios a lender reads first current ratio, quick ratio, debt-to-equity

From the first entry to a set of statements · Working with the numbers

FIFO and LIFO: which cost leaves first inventory: FIFO and LIFO
Weighted average cost inventory: weighted average cost
Break-even: how many you must sell to cover the costs break-even in units and in sales
Markup and margin are not the same number markup versus margin
Simple interest simple interest
Present value of one sum present value of one sum
Payroll: from gross pay to net pay payroll: gross pay to net pay
Sales tax on a sale sales tax on a sale

From the first entry to a set of statements · Becoming licensed

The licence you may not need, which is the first question and not the last the licence you may not need
The education requirement, and the rule that is changing underneath it the education requirement, and the rule changing under it
The examination, and the one requirement that has not moved the examination, and the part that has not moved
The supervised experience, and who is allowed to sign it off the supervised experience, and who signs it off
The board issues the licence, and passing the examination issues nothing the board that issues, and what passing is not
Working across state lines, which is more permissive here than anywhere else on this list working across state lines
The renewal clock, which starts the day the licence is granted the renewal clock

The California road to a CPA licence · Before anything else

First, whether you need it at all whether you need the licence at all
The board issues it. The society does not. the board that issues it, and the society that does not
The one thing only a licensee may do the one thing only a licensee may do

The California road to a CPA licence · The rules are moving under you

When two sets of requirements are valid at once when two sets of requirements are valid at once
Which date decides, and why it is rarely the obvious one which date decides, and why it is rarely the obvious one
Reading a board notice instead of a forum thread reading the board's own notice instead of a forum

The California road to a CPA licence · Education

The shape of the education requirement the shape of the education requirement
A concentration is subjects, not the name on your degree a concentration is subjects, not the name of your degree
A degree earned outside the United States a degree earned outside the United States

The California road to a CPA licence · The examination

The sections everybody takes, and the one you choose the sections everybody takes and the one you choose
The rolling window, and when its clock starts the rolling window, and when its clock starts
Sitting the examination is not the same as being licensed sitting for the examination before you are licensed

The California road to a CPA licence · Experience and ethics

Supervised experience, and who may sign for it supervised experience, and who may sign for it
When study can stand in for part of the experience study standing in for part of the experience
The ethics step, which changed shape the ethics step that changed shape

The California road to a CPA licence · Getting it and keeping it

The order the steps are actually done in the order the steps are actually done in
The renewal clock, and what it asks for the renewal clock and what it asks for
Working across a state line working across a state line

Management and cost accounting · Costs that behave differently

Fixed, variable, and the ones that are both fixed, variable and mixed costs
Splitting a mixed cost, with two months and no statistics splitting a mixed cost with the high-low method
Contribution margin: what each sale leaves behind contribution margin per unit
The contribution margin ratio the contribution margin ratio
How many must we sell to make the profit we want the volume that reaches a target profit
The margin of safety the margin of safety

Management and cost accounting · What a unit really costs

Direct materials and direct labour direct materials and direct labour
The predetermined overhead rate the predetermined overhead rate
Applying overhead, and the amount left over applying overhead, and the amount left over
Absorption costing against variable costing absorption costing against variable costing

Management and cost accounting · Was it the price or the amount

Material: was it the price, or the amount material price and quantity variances
Labour: was it the rate, or the hours labour rate and efficiency variances
Reading a variance without blaming the wrong person reading a variance without blaming the wrong person

Management and cost accounting · Deciding with numbers

Relevant cost, and the money already gone relevant cost, and the cost that is already spent
Make the part, or buy it making a part or buying it
An order at less than the usual price an order at less than the usual price
Dropping a product line dropping a product line

Audit and assurance · What an audit is for

What an audit is actually for what an audit is actually for
Reasonable assurance, and why not absolute reasonable assurance, not a guarantee
Independent in fact, and seen to be independence in fact and in appearance

Audit and assurance · What could be wrong

What management is claiming, line by line what management is claiming when it publishes accounts
Where a misstatement is likely to be where a misstatement is likely to be

Audit and assurance · How much wrong matters

Materiality: how much wrong would change a decision materiality: how much wrong would matter
Why you work to a number below materiality why you work to a number lower than materiality

Audit and assurance · Getting evidence

What makes one piece of evidence stronger than another what makes one piece of evidence stronger than another
Which direction you test in decides what you prove which direction you test in, and what it proves
Testing some of it, and what that costs you testing some of it, and what that costs you
Projecting what you found onto what you did not look at projecting what you found to what you did not look at
Asking somebody outside the company asking somebody outside the company

Audit and assurance · What you conclude

Whether the company will still be here next year whether the company will still be here next year
The four things an audit report can say the four things an audit report can say

Payroll · What the worker is paid

Gross pay, deductions, net pay the shape of gross pay to net pay
Overtime, and the rate it is paid at overtime and premium hours

Payroll · What it costs the business

What a worker costs, against what they are paid what a worker costs against what they are paid
Pay periods, and the weeks that go missing pay periods, and the weeks that go missing

Payroll · Money you are holding for somebody else

Money you are holding for somebody else money you are holding for somebody else
The liability, and the day it has to be handed over the liability, and the day it has to be handed over

Payroll · The books at period end

Worked in one period, paid in the next wages earned in one period and paid in the next
When somebody has been paid too much when somebody has been paid too much

Payroll · Getting it wrong is expensive

Employee or contractor, and why it is not a preference employee or contractor, and why it is not a preference
What has to be kept, and why it is kept that long what has to be kept, and for how long

Fund accounting: government and non-profit · Why the books are split

Why these books are not one set of books why these books are not one set of books
What a fund actually is what a fund actually is

Fund accounting: government and non-profit · Money with strings attached

Money you may spend as you judge best, and money you may not money you may spend as you judge best, and money you may not
Who imposed it, and why that changes what you can do who imposed the restriction, and why it matters

Fund accounting: government and non-profit · The budget is the limit

The budget is an authorisation, not a forecast the budget as an authorisation rather than a forecast
Appropriation, expenditure, and what is left appropriation, expenditure, and what is left

Fund accounting: government and non-profit · Not overspending

Committing money before you spend it committing money before you spend it
What is actually available to spend what is actually available to spend

Fund accounting: government and non-profit · What it all means

A surplus is not a profit a surplus is not a profit
Who reads these accounts, and what they want to know who reads these accounts, and what they want to know

Tax · The books and the return

The books and the return are different documents the books and the return are different documents
Differences that reverse, and differences that never do differences that reverse, and differences that never do

Tax · How a rate actually applies

A rate applies to a band, not to the whole a rate applies to a band, not to the whole
The rate on your next pound, and the rate on all of it the rate on your next pound, and the rate on all of it
Why more income never leaves you with less why more income never leaves you with less

Tax · What may be subtracted

A deduction reduces what is taxed, not the tax a deduction reduces what is taxed, not the tax
A deduction you cannot evidence is not a deduction a deduction you cannot evidence is not a deduction

Tax · Paying it

What was withheld is an estimate, not the bill what was withheld is an estimate, not the bill
Filing and paying are two obligations filing and paying are two obligations

Tax · When it was wrong

When the return was wrong when the return was wrong
Why behaviour changes the number why behaviour changes the number

Forensic accounting · What the work is

What the work actually is what the work actually is
Who the duty runs to who the expert's duty runs to

Forensic accounting · Why it happens

Pressure, opportunity, and the story people tell themselves pressure, opportunity, and the story people tell themselves
The only one of the three an organisation controls the only one of the three an organisation controls

Forensic accounting · How money actually leaves

Taking money before it is ever recorded taking money before it is ever recorded
Covering yesterday's theft with today's receipt covering yesterday's theft with today's receipt
Somebody on the payroll who does not exist somebody on the payroll who does not exist

Forensic accounting · Finding it in the numbers

A screening tool, and the data it does not work on a screening tool, and where it does not hold
Amounts that stop just short of needing approval amounts that stop just short of needing approval
Why one person should not do all of it why one person should not do all of it

Forensic accounting · Making it stand up

Handling evidence so that it survives handling evidence so that it survives
Asking without contaminating the answer asking without contaminating the answer

Engineering 83 lessons

Engineering quick reference: every topic on one page, one line each.

From units to a working design · Units and numbers

Two systems of units, and carrying a number between them SI and US units, and converting between them
Significant figures: how much of the number you actually know significant figures
Let the units check the equation for you checking an equation by its units
Mass is how much stuff; weight is the pull on it force, mass and weight
Density and specific weight: how heavy a volume is density and specific weight

From units to a working design · Statics

A force has a direction, so split it into two you can add vectors and their components
The free-body diagram: the body alone, and every force on it the free-body diagram
Equilibrium of a particle: the forces add to nothing equilibrium of a particle
A moment: how hard a force is trying to turn something moments and the lever
Equilibrium of a rigid body: forces balance and turning balances equilibrium of a rigid body
What each end of a simple beam carries reactions of a simple beam
A truss, one joint at a time a truss by the method of joints

From units to a working design · Strength of materials

Stress: the force, spread over the area that carries it stress: force over area
Strain: how much it stretched, for its length strain: how much it stretches
Hooke's law: stress and strain are proportional, and E is the ratio Hooke's law and Young's modulus
How much a rod stretches: PL over AE axial deformation, PL over AE
Factor of safety: how far the material is from its limit factor of safety
Shear in a pin: the force trying to slice it shear stress in a pin
Thermal expansion: heat makes it longer, and holding it makes it stressed thermal expansion

From units to a working design · Circuits

Ohm's law: push, resistance, and what flows Ohm's law
Electrical power: how fast the circuit turns energy into heat or work electrical power
Series adds; parallel shares series and parallel resistance
Kirchhoff's voltage law: round any loop, the volts add to zero Kirchhoff's voltage law
The voltage divider: two resistors share the volts by their size the voltage divider
A capacitor stores energy, and the energy goes as the square of the volts energy in a capacitor
RMS: the DC voltage that would heat the same wire the same amount RMS of a sine wave

From units to a working design · Fluids and thermo

Pressure at depth: the weight of the column above you pressure at depth
Pascal's principle: the same pressure everywhere, so area multiplies force Pascal's principle and the hydraulic jack
Continuity: what flows in must flow out continuity: flow is area times speed
Bernoulli: pressure, speed and height trade with each other Bernoulli between two points
The ideal gas law: pressure, volume, amount and temperature in one line the ideal gas law
Sensible heat: how much energy to change a temperature sensible heat, Q = m c ΔT
The ceiling on a heat engine efficiency of a heat engine
Work is force through a distance; power is how fast work and power

From units to a working design · Engineering economics and on the job

Interest: simple grows in a line, compound grows on itself simple and compound interest
Present and future value: money moved through time present and future value
Payback: how long until the saving has repaid the cost payback period
Costing a bill of materials costing a bill of materials
Tolerance stacks: when the parts all sit at their limits tolerance stacks
A datasheet in one system, a design in another a unit-conversion chain from a spec

From units to a working design · Becoming licensed

Most engineers are not licensed, and the reason has nothing to do with them the licence many engineers never need, and why that is not about you
What the licence actually lets you do, which is take responsibility in writing what the licence actually lets you do
The degree, and the accreditation that quietly changes how many years you owe the degree, and the accreditation that changes the years
The first examination, and why it is sat while you are still a student the first examination, and why it is sat early
Progressive experience, and who it has to be under progressive experience, and who it has to be under
The second examination, which is the one your branch decided the second examination, which is your discipline's
The board issues, the national body does not, and moving runs on a record the board that issues, and moving between states

From units to a structure that stands up · Loads and how they travel

What is always there, and what comes and goes dead, live and the difference it makes
Every load reaches the ground or the building falls down following a load to the ground
A member carries the area that drains to it which area a member actually carries
Loads are combined before anything is checked why loads are combined before they are checked

From units to a structure that stands up · Members that carry them

Two diagrams that say where a beam is working hardest shear and moment along a beam
Strong enough and still unacceptable how far it moves, and why that governs
Concrete takes compression, steel takes tension concrete works in compression, steel in tension
Choosing a section from the numbers in the table choosing a section from its properties

From units to a structure that stands up · The ground and the site

What the ground underneath will actually hold what the ground will hold
Everything settles; the damage is in the difference settlement, and why differential is the problem
Backsight, foresight, and the level you actually want levelling: backsight, foresight, reduced level
How much water arrives from a piece of ground runoff from a catchment

From units to a machine that keeps running · Turning and transmitting

Torque, speed and power are one relationship torque, speed and power are one relationship
A gearbox buys torque with speed gear ratio trades speed for torque
A shaft twisting under load A shaft in torsion
Bearing life falls off with the cube of the load bearing life falls off with the cube of load

From units to a machine that keeps running · Holding together

A bolted joint is held by clamp, not by the bolt A bolted joint is held by preload, not by the bolt
Rate, deflection, force spring rate, deflection and the force you get
Things break at loads they carried yesterday things break at loads they carried yesterday
Clearance, transition, interference tolerance and fit: clearance, transition, interference

From units to a machine that keeps running · Moving heat and fluid

Head, flow and the power it takes head, flow and the power a pump needs
The margin that stops a pump destroying itself cavitation: the margin that stops it
Moving heat from one stream into another moving heat between two streams
The ceiling no engine beats efficiency, and the ceiling nothing beats

From units to a circuit that behaves · Alternating quantities

Why alternating quantities are drawn as arrows why alternating quantities are drawn as arrows
Resistance that depends on frequency impedance: resistance that depends on frequency
Real power, apparent power, and the gap between real, reactive and apparent power
Three supplies, one root three three phases, and the root-three that follows

From units to a circuit that behaves · Machines and supplies

Turns ratio, and what it does to current turns ratio, and what it does to current
Slip, torque, and the current at the moment of starting slip, torque and starting current
Protection guards the cable, not the appliance sizing protection to the cable, not the load
A fault needs somewhere to go, fast earthing and the fault path

From units to a circuit that behaves · Signals and devices

A component that conducts one way A device that conducts one way
A small current controlling a large one using a transistor as a switch
Two rules that solve most op-amp circuits the two rules that solve most op-amp circuits
Sampling fast enough to be honest sampling fast enough to be honest

IT support 39 lessons

IT support quick reference: every topic on one page, one line each.

From the first ticket to a closed incident · The desk

A ticket is a promise with a number on it what a ticket is
Incident, service request, problem: three words for three different jobs incident, request, problem
Priority is impact times urgency, not who is shouting priority from impact and urgency
The SLA is a clock, and a breach is the clock running out the SLA clock
Escalation: handing it up, with everything you found escalating a ticket
The first reply: what you understood, what you will do, when they will hear the first reply
You cannot do it all, so decide what you are giving up what you are giving up

From the first ticket to a closed incident · Troubleshooting method

Six steps, in the same order every time the six-step method
What changed? The question that finds half of all faults ask what changed
One change at a time, or you will never know which one worked one change at a time
Make it happen on purpose before you try to make it stop reproduce it first
Check from the wall outward: power, cable, link, address, name, service the order you check
When to stop: the time box, the access line, and the data when to stop

From the first ticket to a closed incident · Hardware and the OS

POST and the boot order: what a machine does before the OS exists POST and the boot order
RAM is the desk; storage is the filing cabinet RAM and storage
The disk is full: find the big things, in order a full disk
A slow machine: measure before you blame a slow machine
Safe mode: the operating system with nothing extra loaded safe mode and drivers
A printer that will not print: the queue, the panel, the wire, the spooler a printer that will not print

From the first ticket to a closed incident · Networking numbers

An IP address is a street and a house; the mask says where the street ends IP address and subnet mask
How many machines fit: two to the host bits, minus two usable hosts in a subnet
Is this address on my network? Find the block, then the street is it on my network
DHCP: the address the network hands you, and what 169.254 means DHCP and 169.254
DNS: a name is looked up in a fixed order DNS and how a name is found
ping, then traceroute, then nslookup: three questions in order ping, traceroute, nslookup
How long a file takes: bytes times eight, over bits per second how long a download takes
Bandwidth is how wide the pipe is; latency is how long the pipe is latency and bandwidth

From the first ticket to a closed incident · Accounts and security basics

A password reset: prove who is asking before anything else the password reset
Account lockout: why it locks, and what is usually still trying account lockout
Least privilege: the access the job needs, and none it does not least privilege
MFA: something you know plus something you have MFA
Phishing: the checks, in the order that catches it fastest spotting phishing
When a ticket stops being yours: the security incident when a ticket is a security incident

From the first ticket to a closed incident · Closing the loop

The fix note: what was wrong, what you did, how you know it worked the fix note
The symptom is what they saw; the root cause is why it keeps coming back root cause and symptom
The knowledge article: written so the next person finds it and can follow it the knowledge article
A change request: what, why, what could go wrong, and how to put it back a change request
Backups and 3-2-1: three copies, two kinds of media, one of them somewhere else backups and 3-2-1
RPO and RTO: how much you can lose, and how long you can be down RPO and RTO

Cybersecurity 40 lessons

Cybersecurity quick reference: every topic on one page, one line each.

From a threat to a closed incident · The three words

The three words: secret, unchanged, available the three words: confidentiality, integrity, availability
Threat, vulnerability, risk: three words that are not the same threat, vulnerability and risk
An asset, and the person who owns it an asset and its owner
What the attacker is actually after what an attacker is after
More than one wall defence in depth

From a threat to a closed incident · The common threats, recognised

Phishing: the message that asks you to hurry phishing, and what to check
Malware in four plain words the kinds of malware
Social engineering: attacking the person, not the machine social engineering
Credential stuffing: why one reused password is everybody's problem credential stuffing and reused passwords
Denial of service, seen from inside denial of service, seen from inside
Insider risk: the threat with a badge insider risk

From a threat to a closed incident · The controls

Passwords: length beats cleverness passwords: length over complexity
Proving it is really you, twice multi-factor authentication
Least privilege: only what the job needs least privilege
Patching, and the window you stand in patching and the window
Locked on the shelf, locked in the post encryption at rest and in transit
Hashing is not encryption hashing versus encryption
Reading a rule set from the top reading a firewall rule set
Backups and the 3-2-1 rule backups and the 3-2-1 rule
Logging: what to keep, and for how long logging: what to keep

From a threat to a closed incident · Reading the evidence

One log line, four questions reading a log line
Failed logins: what a count means failed logins in a row
Is that address one of ours? an address and its network mask
Port numbers, and what usually lives there port numbers and what lives there
Comparing a fingerprint comparing a file hash
The order to check a suspicious email checking a suspicious email, in order
A timeline from three log lines a timeline from log lines

From a threat to a closed incident · Responding

The six phases, in order the incident-response phases
Isolate before you investigate isolate before you investigate
Preserving evidence preserving evidence
Who to tell, and when who to tell, and when
Severity: how bad, times how wide severity from impact and scope
The after-action report the after-action report

From a threat to a closed incident · The arithmetic of risk

What one bad day costs: single loss expectancy single loss expectancy
What it costs a year: annualised loss expectancy annualised loss expectancy
Is the control worth it? is the control worth it
Likelihood times impact likelihood times impact
Working out the patch deadline a patch deadline in hours
Password strength as a number of bits password entropy in bits
How long would it take to guess? time to guess a password

Project management 41 lessons

Project management quick reference: every topic on one page, one line each.

From a request to a report that is true · What a project is

A project is temporary work that makes something new a project vs operations
Scope, time and cost: pull one, the other two move scope, time and cost
Stakeholders: everyone the project touches, and the few who decide stakeholders and who decides
The charter: one page that says the project exists and why the project charter
The life cycle: start, plan, do, watch, finish the project life cycle
Predictive or agile: plan it all first, or plan a little and show it often predictive vs agile

From a request to a report that is true · Scope and the work

The work breakdown structure: the whole job, cut into pieces you can hand to someone the work breakdown structure
The 100% rule: the children add up to the parent, exactly the 100% rule
A work package: small enough to estimate, big enough to be worth tracking work packages and their size
The scope statement: what is in, what is out, and how you will know it is done the scope statement
Change control: the change is welcome, the surprise is not change control, in steps
Traceability: every requirement can be followed to the thing that proves it requirements traceability

From a request to a report that is true · Schedule

Dependencies: which activity has to wait for which activities and dependencies
The network diagram: the activities drawn as a chain of boxes and arrows the network diagram
The forward pass: the earliest each activity can start and finish the forward pass (early start, early finish)
The backward pass: the latest each activity can start and finish without delaying the end the backward pass (late start, late finish)
Float: how much an activity can slip before the end date moves float
The critical path: the chain with no room the critical path
Three-point estimates: an honest number from three guesses three-point estimates and PERT
Crashing and fast-tracking: two ways to buy time, at two different prices crashing vs fast-tracking

From a request to a report that is true · Cost and earned value

Estimating: by comparison, by rate, or by adding up the pieces estimating: analogous, parametric, bottom-up
The budget and the baseline: the yardstick you will be measured against the budget and the baseline
PV, EV and AC: what you planned to have done, what you did, what it cost planned value, earned value, actual cost
CV and SV: how far off, in dollars cost and schedule variance
CPI and SPI: what each dollar bought, and how fast CPI and SPI
EAC: what the whole project will cost, if the pattern holds estimate at completion
ETC and TCPI: what is left to spend, and how well you would have to perform estimate to complete and TCPI
Reading the status from two numbers reading a status from the indexes

From a request to a report that is true · Risk and quality

A risk is a sentence: because of this, that might happen, and it would cost this writing a risk: cause, event, effect
Expected monetary value: probability times impact expected monetary value
The risk register: the list that is read every week or not at all the risk register
Five things you can do about a threat risk responses: escalate, avoid, mitigate, transfer, accept
Contingency and management reserve: two pots, two owners contingency and management reserve
A control chart: is the process wobbling normally, or has something changed a control chart
Cost of quality: paying to get it right, or paying for getting it wrong cost of quality

From a request to a report that is true · People and communication

Communication channels: why a bigger team is much harder to keep in step communication channels
RACI: who does it, who answers for it, who is asked, who is told the RACI chart
Forming, storming, norming, performing: a new team is not a team yet the stages of a team
A status report that tells the truth in three numbers a status report in three numbers
Lessons learned: written so the next project can use them lessons learned
Closing a project: it is over when the signatures say so closing a project, in order

Nursing 41 lessons

Nursing quick reference: every topic on one page, one line each.

From a unit conversion to a safe medication pass · Units

The metric ladder: every rung is a thousand the metric ladder: g, mg, mcg, L, mL
Kilograms from pounds: divide by 2.2 kilograms from pounds
Hours, minutes and the 24-hour clock hours, minutes and the 24-hour clock
Reading a label: how much drug in how much liquid reading a label: strength per volume
Round as the problem states, and only at the end rounding as the problem states

From a unit conversion to a safe medication pass · Dose calculation

Desired over have, times quantity desired over have, times quantity
Tablets from an order tablets from an order
A liquid dose: how much of the bottle a liquid dose in mL
Weight-based dosing: the order is per kilogram weight-based doses, mg/kg
A daily dose split across the day a daily dose split across the day
Does the answer make sense by size does the answer make sense by size

From a unit conversion to a safe medication pass · IV rates

mL per hour: the number the pump wants mL per hour from volume and time
Drops per minute: when there is no pump drops per minute
How long the bag will take how long an infusion takes
A piggyback: a small bag over a short time a piggyback over thirty minutes
mcg/kg/min to mL/h: the long chain, one link at a time mcg/kg/min to mL/h
A bolus: a set volume, fast a bolus over a short time

From a unit conversion to a safe medication pass · Fluids and intake

Intake and output: two columns, one total each intake and output over a shift
A percent solution is grams in every 100 mL percent solutions: g per 100 mL
Diluting a solution: C1V1 = C2V2 diluting a solution: C1V1 = C2V2
Maintenance fluids by the 4-2-1 rule the problem states maintenance fluids by the 4-2-1 rule
Net balance: what came in, less what went out net fluid balance

From a unit conversion to a safe medication pass · The fundamentals in order

Hand hygiene: the order, and the twenty seconds hand hygiene, in order
The rights of medication administration, in order the rights of medication administration
Two identifiers, and what does not count as one two patient identifiers
Vital signs: the order they are taken, and the arithmetic in them vital signs: the order, and the ranges given
A sterile field, and the ordinary things that break it a sterile field, and what breaks it
A lift transfer, in the order that keeps everyone upright a lift transfer, in order
Protective equipment: on in one order, off in another isolation precautions: PPE on and off
SBAR: four boxes, in order, in under a minute SBAR handoff

From a unit conversion to a safe medication pass · On the shift

A med pass, end to end a med pass, end to end
A set of vitals has changed: what comes first a change in vitals: what first
Documentation: what, when, and how a mistake is corrected documentation: what and when
After a medication error: the order of the next few minutes after a medication error
Prioritising by the ABC rule, as it is stated prioritising by ABC
Reading a line on the medication record reading a MAR line

From a unit conversion to a safe medication pass · Getting and keeping the licence

Two applications, to two organisations, and neither knows about the other the two applications, and who they go to
The Authorization to Test: what you are actually waiting for the Authorization to Test, and its clock
Passing the examination is not the licence why passing the examination is not the licence
Moving a licence to another state is an application, not a transfer moving a licence to another state
The multistate licence, and the states it does not cover the multistate licence, and who is not in it

Pharmacy 46 lessons

Pharmacy quick reference: every topic on one page, one line each.

From a conversion to a filled prescription · Units and reading

The metric ladder: one step is a thousand the metric ladder: grams, milligrams, micrograms
Millilitres, litres, and the cc millilitres, litres and the cc
Pounds on the chart, kilograms in the order pounds to kilograms
Kitchen measures, written in millilitres teaspoonfuls and tablespoonfuls in millilitres
Roman numerals on a script roman numerals on a script
The sig, in plain words sig abbreviations in plain words
The parts of a prescription the parts of a prescription

From a conversion to a filled prescription · Days' supply and quantity

How much to dispense how much to dispense
How many days the bottle lasts how many days the bottle lasts
Days' supply from an insulin vial days' supply from an insulin vial
Puffs in a canister puffs in a canister
Eye drops, at 20 drops to the millilitre eye drops, at 20 drops to the millilitre
Refills, and when the next one is due refills and the last fill date

From a conversion to a filled prescription · Dose calculation

Desired over have, times the quantity desired over have, times the quantity
A liquid dose in millilitres a liquid dose in millilitres
A dose written in milligrams per kilogram a dose written in milligrams per kilogram
A child's dose, exactly as the order writes it a child's dose, as the order writes it
A dose out of a percent strength a dose from a percent strength
Check the answer by size before you write it checking the answer by size

From a conversion to a filled prescription · Concentrations and dilutions

Percent strength: grams in a hundred millilitres percent strength, weight in volume
Ratio strength: one gram in so many millilitres ratio strength
C1V1 = C2V2: the drug does not change diluting a stock (C1V1 = C2V2)
Alligation: mixing a strong one and a weak one alligation: mixing a strong and a weak
How much diluent to add how much diluent to add
Parts per million parts per million

From a conversion to a filled prescription · Compounding and IV

Reducing and enlarging a formula reducing and enlarging a formula
Making a batch from a recipe making a batch from a recipe
Millilitres an hour millilitres an hour
How long the bag will run how long the bag will run
Drops a minute drops a minute
Milliequivalents from milligrams milliequivalents from milligrams
Reconstitution: the powder takes up room reconstituting a powder

From a conversion to a filled prescription · The counter

AWP, markup and the dispensing fee AWP, markup and the dispensing fee
The copay and what the plan pays the copay and the patient's share
A percent discount a percent discount
Inventory turnover inventory turnover
Expiry dates and beyond-use dates expiry and beyond-use dates
The order a prescription is filled in the order a prescription is filled in
The final check the final check
Look-alike, sound-alike look-alike, sound-alike names

From a conversion to a filled prescription · Becoming licensed

The intern hours, and the fact that nobody can quote you the number the intern hours, and who sets the number
One profile, and everything attaches to it the profile everything attaches to
Two examinations, and only one of them is the same everywhere the two examinations, and why only one of them is national
The board issues the licence, and the papers are not it the board that issues, and what passing is not
Moving state, and the state that does not allow it moving to another state, and the state that will not
A licence with a date on it the renewal clock

Medicine foundations 42 lessons

Medicine foundations quick reference: every topic on one page, one line each.

From a unit to a physiology you can calculate · Units and the body's numbers

The same blood, two units: mmol/L and mg/dL mmol/L and mg/dL
Pounds to kilograms, feet and inches to centimetres pounds to kilograms, feet and inches to centimetres
Body mass index: kilograms over metres squared body mass index
Body surface area: one square root, in centimetres and kilograms body surface area
Fahrenheit to Celsius: subtract, then five ninths Fahrenheit to Celsius
A reference range is two numbers and a rule a reference range, and what within it means

From a unit to a physiology you can calculate · The heart and the vessels

Heart rate off a rhythm strip: 300 over the large squares heart rate from a rhythm strip
Two numbers on a cuff, and the two figures you take from them pulse pressure and mean arterial pressure
Cardiac output: how much blood the heart moves in a minute cardiac output
Ejection fraction: the share of a full ventricle that leaves ejection fraction
Blood volume: a set number of millilitres for every kilogram blood volume from body weight

From a unit to a physiology you can calculate · The lungs and the kidneys

Minute ventilation: one breath, times the breaths in a minute minute ventilation
Dead space: the part of every breath that does no work dead space and alveolar ventilation
Cockcroft-Gault: an equation you substitute into creatinine clearance by Cockcroft-Gault
Urine output: millilitres per kilogram per hour urine output in mL per kg per hour
The anion gap: what the measured ions do not account for the anion gap
The 4-2-1 rule: maintenance fluid in three slices maintenance fluid by the 4-2-1 rule

From a unit to a physiology you can calculate · Cells, genes and statistics

Dilutions, and turning a count into a concentration dilutions and counting cells
The Punnett square: four boxes, and the fractions fall out the Punnett square and Mendelian fractions
Hardy-Weinberg: two frequencies that add up to one the Hardy-Weinberg equation
Sensitivity and specificity: two columns of one table sensitivity and specificity
Positive predictive value: what a positive result is worth here positive predictive value
Absolute risk, relative risk, and how many people absolute risk, relative risk and number needed to treat

From a unit to a physiology you can calculate · Pharmacology arithmetic

Half-life: halve it, and halve it again half-life, and what is left after n of them
The loading dose: fill the space first the loading dose
The maintenance rate: replace exactly what is cleared the maintenance rate
A figure written per kilogram is one multiplication a dose in mg per kilogram
From micrograms per kilogram per minute to millilitres per hour an infusion in mL per hour
Bioavailability: the fraction that actually gets in bioavailability as a fraction

From a unit to a physiology you can calculate · Procedures in order

Hand hygiene: the order is the technique hand hygiene, in order
Putting on sterile gloves without touching the outside putting on sterile gloves
A vital-signs round, in the order it is done a vital-signs round, in order
ABCDE: an order of looking, agreed in advance the ABCDE primary survey
A history in the standard order taking a history in the standard order
SBAR: a handover in four letters SBAR, and the handover
Consent before a procedure, as a sequence consent before a procedure

From a unit to a physiology you can calculate · Becoming licensed

An accredited school, or the certification that stands in for one the accredited school, and what an international graduate needs instead
The national examinations, and the thing they are not the national examination sequence, and what passing it is not
The postgraduate years, and why nobody can tell you the number the postgraduate years, and why the number is not the same everywhere
The board issues the licence, and decides a good deal for itself the board that issues, and what it decides for itself
The expedited pathway, and what it still asks of you the expedited pathway, and the state of principal license
A licence has a date on it the renewal clock, and what it asks of you

Law foundations 57 lessons

Law foundations quick reference: every topic on one page, one line each.

From a word to a case that is in order · The map

Two kinds of case, and the four questions that tell them apart civil cases and criminal cases
Who is who, and why the words change as the case moves what each side is called
How sure the court has to be the standard of proof
The court that hears the evidence, and the court that reads the record trial courts and appeal courts
Three kinds of written law, and which one to read first statute, regulation, case law
Precedent, and the difference between must and might precedent, and what binding means
Reading a citation as a set of boxes reading a case citation

From a word to a case that is in order · The elements

A claim is a list, and every line has to be ticked a claim is a list of elements
Negligence: four lines, always the same four the elements of negligence
How a contract is made, in the order it happens how a contract is formed
Breach: what was promised, what was done, what it cost breach of contract
A crime is an act plus a state of mind act and mental state
A defence is a list too defences, as a list
Who has to prove it, and what happens if nobody does who has to prove it

From a word to a case that is in order · Civil procedure in order

The life of a civil case, start to finish the life of a civil case
The complaint and the answer, paragraph by paragraph complaint and answer
Service of process, step by step service of process
Discovery: the four ways each side sees what the other has the tools of discovery
A motion asks the court for one thing what a motion asks for
A civil trial, in the order it happens a civil trial, in order

From a word to a case that is in order · Criminal procedure in order

The life of a criminal case, start to finish the life of a criminal case
The rights told to a person under arrest the rights read at arrest
The first court date, and the question of release first appearance and bail
The plea, and what each one does to the case the plea options
What an appeal can do and what it cannot what an appeal can do

From a word to a case that is in order · Counting and dates

Counting a deadline from the rule you were handed counting a deadline
A limitation period, and the day it runs out a limitation period
A fee schedule is a list of prices and a count of things a fee schedule total
Interest on a judgment, at the rate the order gives interest on a judgment
Damages arithmetic: add the losses, then apply the reductions damages arithmetic

From a word to a case that is in order · The office

Reading a file you have never seen, in order reading a file in order
The parts of a contract, in the order they sit on the page the parts of a contract
A chronology: one line, one date, one fact drafting a chronology
The conflict check, and when it happens a conflict check
Confidentiality and privilege are two different things confidentiality and privilege
The checklist before anything goes to the court a filing checklist

From deciding to apply to a California licence · Getting in

A test of one skill, not of what you know about law the admission test: what it measures
Find the job before you read the answers arguments: what the question is really asking
Read for the shape, not for the detail reading: holding a long passage in order
What a school is actually reading the file a school reads
The same file is worth more in October than in February why the same file is worth more in October

From deciding to apply to a California licence · The California examination

Four kinds of law school, and what each one permits four kinds of law school, and what each one permits
An examination after the first year, for some students the first-year students' examination
California sets its own examination the California examination, part by part
An essay is graded on the road, not the destination how an essay answer is graded
A task, a file, and a library the performance test: a task, a file, a library

From deciding to apply to a California licence · Admission, and keeping it

A separate examination on the duties of the job the professional responsibility examination
The application that takes longest and is started last moral character: the application that takes longest
A pass is not a licence from a pass to a California licence
Keeping it in good standing keeping a licence in good standing

From deciding to apply to a Texas licence · The Uniform Bar Examination

One examination, three instruments one examination, three instruments
The multiple-choice day is a test of elimination the multiple-choice day
Essays on subjects announced in advance essays on subjects announced in advance
A score that travels, and what it cannot do A score that travels, and what it cannot do

From deciding to apply to a Texas licence · Admission, and keeping it

The part that is only about this state the part that is only about this state
Character and fitness: file it early because it is slow character and fitness: file it early
A pass is not a licence from a pass to a Texas licence

Teaching 205 lessons

Teaching quick reference: every topic on one page, one line each.

From a blank room to a lesson that lands · How learning actually works

What a person can hold at once how much a person can hold at once
The three kinds of load, and the only one you cut the three kinds of cognitive load
New learning has to stick to something new learning sticks to what is already known
Forgetting is the normal case the forgetting curve
Spacing: the same minutes, further apart spaced practice
Being asked is how it sticks retrieval practice
Mixing the problems up interleaving
A class that nods has not learned the illusion of fluency

From a blank room to a lesson that lands · Designing a lesson

An objective is something you can watch happen an objective you can watch happen
Write the check first backward design: write the check first
I do, we do, you do, and the trap in the middle gradual release of responsibility
A novice needs to see it done worked examples, and fading them
Thinking aloud is the part they cannot see modelling by thinking aloud
Check every few minutes, not at the end checking for understanding mid-lesson
Wait time, cold call, and the hand that is always up wait time and cold call
The exit ticket, and what you do with it tonight the exit ticket

From a blank room to a lesson that lands · Teaching reading

A phoneme is a sound, not a letter a phoneme is a sound, not a letter
Blending and segmenting are two different jobs blending and segmenting
Letters map to sounds, and the map is teachable phonics, where letters map to sounds
Six syllable types, and where to cut a long word the six syllable types
Prefix, root and suffix prefix, root and suffix
Words correct per minute, and what it does not tell you words correct per minute
The running record, and its three bands the running record and its three bands
Words come in three tiers vocabulary in three tiers
Decoding times language comprehension decoding times language comprehension

From a blank room to a lesson that lands · The numbers a teacher actually does

A weighted grade a weighted grade
A rubric, and turning it into a percentage scoring against a rubric
A percentile is not a percentage percentile against percentage
Growth against proficiency growth against proficiency
The mean, the median, and the average that hides two groups mean, median, and the average that hides two groups
Attendance, and the minutes that are gone attendance and the minutes lost
Minutes per objective, and what has to come out pacing a unit

From a blank room to a lesson that lands · Running the room

A procedure taught is a behaviour problem prevented teaching a procedure
The first five minutes the first five minutes
What a transition costs what a transition costs
Positive narration positive narration
De-escalation, in order de-escalation, in order
A ladder you follow rather than invent a consequence ladder
Where a learner sits where a learner sits

From a blank room to a lesson that lands · The duties that are law

Mandated reporting: you report a suspicion mandated reporting
Student records, and who may see them student records and who may see them
The parts of an individualised education programme the parts of an individualised education programme
A 504 plan against an education programme a 504 plan against an education programme
A learner who is learning the language as well as the subject supporting a multilingual learner
When a student reports harassment when a student reports harassment
Confidentiality, and the staffroom confidentiality, and the staffroom

From a degree to a classroom, in whichever state you are in · Getting in, and what you will sit

Every route runs through a programme the state has approved the approved programme every route runs through
Three kinds of examination, and neither your route nor your opinion decides which you sit the three kinds of examination, and who decides which apply

From a degree to a classroom, in whichever state you are in · The parts that wait on other people

The background check is the one step whose clock belongs to somebody else the background check, and whose queue it is
You apply, the programme recommends, the state issues who applies, who recommends, and who issues

From a degree to a classroom, in whichever state you are in · Keeping it, and moving with it

A credential is a licence with a clock on it the renewal clock, and what it asks of you
Reciprocity is the right to apply, not a licence that travels what reciprocity actually gets you

From a degree to a Texas classroom · The route in

Three doors into a Texas classroom, and only one pays you while you train the routes into a Texas classroom
What a programme wants before it will let you in what a programme asks before it admits you
The content examination: proving you know the subject itself the content examination for your field
The second examination: how you teach, not what you know the examination on pedagogy and professional responsibilities
The reading examination elementary candidates sit the reading examination elementary candidates take

From a degree to a Texas classroom · The classroom year

Clinical teaching or a paid internship: the fork that decides your year clinical teaching against a paid internship
The intern certificate: the one that does not get a second year the intern certificate, and why it is not the probationary one
The probationary certificate: how a district can pay you before you are finished the probationary certificate
Somebody watches you teach, and it is written down the observations a candidate must receive
The mentor: the person in the building whose job is you the mentor a first-year teacher is assigned

From a degree to a Texas classroom · Getting it and keeping it

Fingerprints: the step with a queue and no shortcut fingerprinting and the background check
The order the application is actually done in the order the application is done in
The standard certificate, and the clock it starts the standard certificate and its term
Keeping it: hours across the renewal cycle continuing professional education across the cycle
Adding a field to a certificate you already hold adding another field to a certificate you hold

The mathematics on the content examination · Number and how it is written

Place value: the position is doing the work place value, and why the position is the whole idea
Rounding is choosing which of two numbers you are nearer to comparing, ordering and rounding
Regrouping is trading ten of one place for one of the next adding and subtracting, and what regrouping really is
Multiplication is repeated addition, an array, and a rectangle multiplication, from an array to the algorithm
Two different questions both called division division: sharing, grouping, and the remainder
Factors, multiples and the numbers that have neither factors, multiples and primes

The mathematics on the content examination · Fractions, decimals and percent

A fraction is one number, not two what a fraction actually is
Equivalent fractions: the same number, cut more finely equivalent fractions and simplest form
Three ways to see which fraction is bigger comparing fractions without a calculator
You cannot add pieces of different sizes adding and subtracting fractions
Multiplying is easy and dividing is multiplying upside down multiplying and dividing fractions
Decimals are fractions whose denominators are all tens decimals, and the operations on them
Percent is a fraction out of a hundred, and it asks three questions percent, and the three questions it asks
A ratio compares parts; a proportion says two ratios match ratio and proportion

The mathematics on the content examination · Algebraic thinking

Negative numbers are directions, not smaller positives negative numbers and the number line
The order of operations is a convention, and it has a reason expressions, variables and the order of operations
Solving is undoing, in the reverse of the order it was built solving an equation by undoing it
A rule that turns any input into its output patterns, rules and what a function is

The mathematics on the content examination · Shape, measure and data

Converting a unit is multiplying by one measurement, and converting a unit without guessing
Perimeter is a length; area is a covering perimeter and area
Volume fills, surface area wraps volume and surface area
Shapes are classified by what they must have, not what they look like classifying shapes, and the angles inside them
Along the corridor, then up the stairs the coordinate plane
Four numbers that summarise a set, and when each one lies mean, median, mode and range, and which one answers the question
Which graph for which question, and the ones that mislead reading a graph, and the ones that mislead
Probability is a count, not a feeling probability, counted rather than felt

The science on the content examination · Living things

Seven things a living thing does, and a car does four of them what makes something living
Everything alive is made of cells, and plant cells have three extra parts cells, and what they are the unit of
Grouping by what a thing is, not by where it lives classifying living things
A plant builds its own food out of air and water how a plant feeds itself
Cycles, and what is passed on rather than picked up life cycles and inherited traits
Arrows point the way the energy goes food chains, food webs and what eats what
Adaptations are not chosen, and individuals do not acquire them adaptation, and how it comes about
Systems that each do one job and all depend on the others the human body systems

The science on the content examination · Earth and space

Three kinds of rock, and one is made of the other two rocks, minerals and the rock cycle
Three words for three different jobs weathering, erosion and deposition
The surface is broken into plates and they are moving now inside the Earth, and why it moves
The same water, going round, driven by the sun the water cycle
Weather is today and climate is the pattern weather against climate
Tilt gives seasons, spin gives day, orbit gives the year day, year, seasons and phases

The science on the content examination · Matter and energy

Same particles, different arrangement states of matter, and what changes between them
Can you get it back? That is the test physical change against chemical change
A force is a push or a pull, and balance means no change forces and motion
Energy is transferred and never made energy, and the fact that it is never made
Both are waves, and only one needs something to travel through light and sound
A circuit has to be a complete loop circuits and magnets

The science on the content examination · Doing science

One thing changed, one thing measured, everything else held still the fair test, and the three kinds of variable
The instrument decides how good the answer can be measuring, and choosing the instrument
What a result can say, and what it cannot what a result can and cannot tell you

The social studies on the content examination · How a country came to be

The continent was full before anybody arrived the peoples who were here first
What crossed the ocean in both directions exploration, and what contact cost
Three regions, three economies, one later argument the colonies, and why they differed
A tax argument that became an argument about consent the road to independence
A government designed by people who did not trust government the Constitution, and the argument inside it
The country grew, and the growth had people living on it expansion west, and who paid for it
The war was about slavery, and the peace was unfinished slavery, the Civil War and Reconstruction
Factories, arrivals, and cities that grew faster than they could cope industry, immigration and the cities
Rights written down and then fought for, one at a time the long fight for civil rights

The social studies on the content examination · How it is governed

Three branches, each able to stop the other two three branches, and why there are three
Three levels, and the level decides what it may do federal, state and local
Most bills die, and the stages are where they die how a bill becomes law
What you are owed, and what is asked of you rights, and the duties beside them
Who may vote, how it is counted, and why turnout decides things voting, elections and why turnout matters

The social studies on the content examination · Where things are

Four things to read before you read the map reading a map: scale, key, grid and direction
Five questions that work on any place the five questions geography asks
A region is anywhere that shares something, and somebody drew the line regions, and why they are drawn where they are
Continents, oceans, and the lines that are not really there continents, oceans and the lines on the globe
People change a place, and the place changes back how people change a place and are changed by it

The social studies on the content examination · How people get what they need

Every choice costs the thing you did not choose scarcity, and the cost of every choice
Price is where two pressures meet supply, demand and what sets a price
Goods you can hold, services you cannot, and nearly everybody is both producers, consumers, goods and services
Money is a tool for three jobs money, saving and what a bank is for

The social studies on the content examination · Reading the past

Who made this, when, and why primary and secondary sources
The questions historians argue about, and how to run that argument the questions historians disagree about

The basic skills test, before anybody teaches you to teach · Which test, and whether you sit it at all

One gate, two names, and your state picks which which basic skills test your state sets, and what it is for
You may not have to sit this at all the ways out: when you do not have to sit it at all
What passing means, and why the total is not the whole story how it is scored, and what passing actually means
The calendar, and what a retake really costs when to sit it, and what a retake costs you
Planning backwards, and practising the weak thing planning backwards from the test date

The basic skills test, before anybody teaches you to teach · Reading

The main idea is what the whole passage is for the main idea, and the answer that is true but too small
What it said, not what you remember it saying what the passage said, as against what you remember
What must follow, not what probably would what follows, and what merely sounds sensible
The meaning it has here a word's meaning in this passage, not in general
How it is built, and why how a passage is built, and why the author built it
Two passages, and a chart beside a text two passages that disagree, and a chart beside a text

The basic skills test, before anybody teaches you to teach · Writing: the mechanics they test

One sentence, and the three ways it stops being one fragments, run-ons and the comma splice
Subject with verb, pronoun with the thing it stands for subject and verb, pronoun and antecedent
A modifier attaches to whatever is nearest the modifier attached to the wrong thing
Three marks that carry most of the questions commas, semicolons and the apostrophe
The words that get swapped, and lists that keep their shape the words that get swapped, and keeping a list parallel
Citing a source, and what a citation is for citing a source, and what a citation is for

The basic skills test, before anybody teaches you to teach · Writing: the essays

The argument essay, and what the rubric actually rewards the argument essay, and what its rubric rewards
The essay built from two sources the essay built from two sources
Ten minutes of planning buy you twenty the ten minutes of planning that buy you twenty
Where the minutes go, and what to do when they run out thirty minutes, and where they go

The basic skills test, before anybody teaches you to teach · Mathematics

Number and quantity, at the level this test asks number and quantity, at the level this test asks
Solving, rearranging, and what a function is linear equations, inequalities and what a function is
Area, volume, angles and the right-angled triangle area, volume, angles and the right-angled triangle
Averages, spread, and the graph they give you averages, spread, and reading the graph they give you
Probability, counted rather than felt probability and counting, without a formula sheet
Turning a sentence into arithmetic turning a sentence into arithmetic
Estimation, and catching your own wrong answer estimation, and catching your own wrong answer

Fine arts, health and physical education · Visual art

The seven things you can point at in any picture the elements of art, which are what you point at
The principles are what you do with the elements the principles of design, which are what you do with them
What each material is actually good for media and processes, and what each one is good for
Enough history to place a work, and no pretending art across time and cultures, without pretending to be an expert
Four questions that turn looking into a lesson responding to art, and the four questions that make it teachable

Fine arts, health and physical education · Music

The elements of music, named the elements of music: beat, rhythm, pitch and the rest
Enough notation to teach from reading enough notation to teach from it
Singing and playing with a class you have all day singing and playing in a primary classroom
Periods, traditions, and why the labels are useful music across time and cultures, and why the labels matter

Fine arts, health and physical education · Theatre, dance and putting the arts to work

Drama in a room with thirty chairs drama in a classroom that is not a theatre
Movement as a subject, with words for it the elements of dance, and movement as a subject
Integrating the arts without turning them into decoration integrating the arts without making them decoration

Fine arts, health and physical education · Health

Nutrition, taught without shaming anybody nutrition, and teaching it without shaming anybody
Body systems and personal health at this age body systems and personal health at this age
Safety, first aid, and what the school actually requires of you safety, first aid and what a school actually requires
Mental, emotional and social health in a primary room mental, emotional and social health in a primary classroom

Fine arts, health and physical education · Physical education

The order children actually acquire movement in motor skills, and the order children acquire them in
The components of fitness, and what each one actually is the components of fitness, and what each one is
A games lesson that is a lesson games, rules and the lesson that is not a free-for-all
A lesson that includes the child who dreads it a physical education lesson that includes everybody

Fine arts, health and physical education · How children develop

Physical, cognitive and social development, stage by stage physical, cognitive and social development, stage by stage
What changes at the top end of primary what changes at the top end of primary

From a degree to a California classroom · What you must show before you start

The degree, and the transcript somebody else has to read the degree and the transcript the Commission reads
Basic skills: one requirement, several doors the basic skills requirement, and the ways to meet it
Subject-matter competence: the examination or the programme subject-matter competence, by examination or by programme
One class all day, or one subject all day a multiple subject credential against a single subject one
Showing you can teach reading the requirement on teaching reading and literacy

From a degree to a California classroom · The preparation programme

The approved preparation programme, and what is inside it an approved preparation programme, and what is in it
Supervised student teaching: the hours somebody signs for the supervised student teaching inside it
The teaching performance assessment: your own teaching, submitted the teaching performance assessment
The Constitution requirement, and two ways to clear it the United States Constitution requirement

From a degree to a California classroom · Credential and clearing

The certificate of clearance: the first document, and the one people forget the certificate of clearance and fingerprinting
The preliminary credential: real, and on a clock the preliminary credential and its term
Induction: the years somebody walks beside you induction, and what clearing a credential means
The clear credential the clear credential
The renewal cycle, and the thing California does not ask for the renewal cycle

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Every lesson on Hone, in teaching order

Python 102 lessons

Your first code · Values and names

Your first code · Doing things

Your first code · Numbers that behave

Your first code · Lists of things

Your first code · Deciding and repeating

Your first code · Looking things up

Your first code · Objects that remember

Read code you did not write · Which is which

Read code you did not write · The traps

Read code you did not write · What it costs

Read code you did not write · Say why

Read code you did not write · Prove it works

Job-ready fundamentals · Reach for the right structure

Job-ready fundamentals · The classics

Job-ready fundamentals · Say it in the interview

Keep the edge · Deep water

Keep the edge · Money and time

Keep the edge · Data at scale

Data structures and algorithms · Things in a line

Data structures and algorithms · Things in a grid

Data structures and algorithms · Things in a tree

Data structures and algorithms · Things in an order

Data structures and algorithms · Things joined to things

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JavaScript 75 lessons

Data structures and algorithms · Things in a line

Data structures and algorithms · Things in a grid

Data structures and algorithms · Things in a tree

Data structures and algorithms · Things in an order

Data structures and algorithms · Things joined to things

JavaScript for the web · Values

JavaScript for the web · Arrays

JavaScript for the web · Truth and equality

JavaScript for the web · Functions and scope

JavaScript for the web · Async

JavaScript for the web · Objects and classes

JavaScript for the web · Prove it works

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TypeScript 107 lessons

Data structures and algorithms · Things in a line

Data structures and algorithms · Things in a grid

Data structures and algorithms · Things in a tree

Data structures and algorithms · Things in an order

Data structures and algorithms · Things joined to things

TypeScript, properly · Why types

TypeScript, properly · Shapes

TypeScript, properly · Narrowing

TypeScript, properly · Generics and beyond

TypeScript, properly · Classes and interfaces

TypeScript, properly · Prove it works

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SQL 52 lessons

Queries that hold up · It ran, and it lied

Queries that hold up · Filter at the right moment

Queries that hold up · A question inside a question

Queries that hold up · One row per thing, and what it costs

Queries that hold up · Changing data without regret

SQL for the workplace · Ask a question

SQL for the workplace · Count and sum

SQL for the workplace · Join the tables

SQL for the workplace · Nothing is something

SQL for the workplace · The real reports

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Regex 52 lessons

Regex that reads · Literal to pattern

Regex that reads · How many

Regex that reads · Where

Regex that reads · The sharp edges

The pattern that is right about your data · Which call, and what it hands back

The pattern that is right about your data · Change the text, not just find it

The pattern that is right about your data · A flag changes the whole meaning

The pattern that is right about your data · The data is not ASCII

The pattern that is right about your data · Fast, or hanging

The pattern that is right about your data · When not to reach for one

The pattern that is right about your data · Prove the pattern

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Git 62 lessons

Git without fear · The three areas