CONSTELLATIONS BY SEASON
the northern evening sky through the year: 28 constellations per the Yale Bright Star Catalogue, latitude 40° N, evenings near 9 pm
METEOR SHOWERS
the twelve principal showers of the year · periods, peaks and ZHR per the IMO calendar
PHASES OF THE MOON
eight phases · a full cycle of 29.53 days
THE SOLAR SYSTEM
eight planets · size, distance, year and day
THE NAMES OF THE ASANAS
twenty foundational poses: Sanskrit, the searchable spelling, the English name — and how old each one is
BLOOD PRESSURE CATEGORIES
the six AHA categories · 2025 guideline · the higher of the two readings decides
DRESS CODES
six lines that turn up on an invitation, and what each one actually asks for — after Debrett’s
THE CHILD IMMUNIZATION SCHEDULE
Table 1 of the CDC schedule, by age: all twenty rows from birth to 18 years, United States, 2025
LAUNDRY CARE SYMBOLS
the 28 symbols of the everyday clothing tag per ISO 3758:2023: five treatments in a fixed order, sharing one set of modifiers
MAGNESIUM COMPOUNDS
the share of magnesium in the salt, computed from the formula · and what human trials measured
DEVELOPMENTAL MILESTONES · YEAR ONE
2, 4, 6, 9, 12 months per the CDC checklists (2022 revision): 59 milestones that at least 75% of children reach by each age
DEVELOPMENTAL MILESTONES · YEAR TWO
15, 18, 24 months per the CDC checklists (2022 revision): 41 milestones that at least 75% of children reach by each age
SIZE CHARTS
shoes, tops, bottoms — and a centimetre under every grid
SERUM ACTIVES
when to apply, what to keep apart in time, what the season changes
THE STAGES OF SLEEP
light, deep and REM as honest shares of the night — and the 90–110 minute cycles it is built from
AI MILESTONES
ten tasks, the year of each, the system, the figure — and the human it was measured against
THE ASCII TABLE
all 128 positions: the column is the three high bits, the row is the four low ones
AUDIO FORMATS
who published each standard, when, what it does to the sound, and how many bits per second it allows
THE BASE32 ENCODING
forty bits to a quantum: five bytes, eight characters and five padding cases
THE BASE64 ENCODING
three bytes become four characters: the alphabet, the tail, and what the "=" at the end is for
BIG-O NOTATION
the seven growth classes: how many steps, how long they take and how far each one lets you go
THE CRON EXPRESSION
the five schedule fields: what each one means, what values it takes, and how to read stars, lists and steps
CSS GRID
the container properties and the item properties per the css-grid-2 specification — and what each does to the layout
BITS, BYTES, KILOBYTES
two scales · 1000 and 1024 · why a drive looks smaller
THE DMX512 PROTOCOL
512 channels down one serial wire, and why a full universe cannot refresh faster than 44 times a second
EAN-13
how thirteen digits become 95 modules of bars and spaces
A NUMBER IN 32 BITS
sign, exponent and significand: what actually sits in a float and what does not
FLOWCHART SYMBOLS
10 shapes, and one algorithm drawn with them
GO vs RUST
seven questions, the same to both, and the document each answer is written in
HTTP METHODS · 2026
ten methods per RFC 9110, 5789 and 10008: which are safe, which are idempotent, which can be retried
HTTP STATUS CODES
five classes · twenty codes you meet every day
SPECIAL-PURPOSE IPv4 BLOCKS
14 blocks that belong to no host on the internet — 13.8 % of the address space, of which exactly one eighth is multicast and reserved
IPv6 ADDRESS NOTATION
eight groups of sixteen bits, the double colon, and one canonical spelling out of thousands
JAVASCRIPT vs GO
seven questions, the same to both, and the document each answer is written in
JAVASCRIPT vs RUST
seven questions, the same to both, and the document each answer is written in
KANBAN
the board, the limit on work in progress, and the four metrics that measure flow
LANGUAGE CODES
487 rows in ISO 639-2; 183 languages also have a two-letter code and 20 have two three-letter ones — and the tag is always the shortest
LIFE CYCLE MODELS
the same steps arranged five ways: the document, the year, and what one turn of the loop covers
MARKDOWN SYNTAX
headings, emphasis, lists, links and code per the CommonMark 0.31.2 specification — the core all dialects share
MEDIA TYPES
2322 registered subtypes under 11 top-level types, and how to read one you have never seen
THE MIDI PROTOCOL
one top bit separates status from data, seven commands per channel, and how much time a serial wire actually takes
POSIX SIGNALS
Twenty-seven signals, five default actions — and two that cannot be caught, ignored or blocked
PYTHON vs GO
seven questions, the same to both, and the document each answer is written in
PYTHON vs JAVASCRIPT
seven questions, the same to both, and the document each answer is written in
PYTHON vs RUST
seven questions, the same to both, and the document each answer is written in
REGULAR EXPRESSIONS
anchors, classes, quantifiers and groups: what a pattern is made of and how it reads, token by token
TIMESTAMPS
date, time and offset from UTC in one string: what it is made of and what it is not
SEMANTIC VERSIONING
what each of the three numbers means, what may follow them, and the order versions stand in