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
MARS
size, distances and time — computed from rotation, orbit and mass
SPRING AND NEAP TIDES
the Earth–moon–sun geometry that makes the tides swing — after NOAA
BLOOD PRESSURE CATEGORIES
the six AHA categories · 2025 guideline · the higher of the two readings decides
CPR AND CHOKING
the 2025 American Heart Association algorithms, step by step — bystander, trained rescuer, and choking at three ages
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
NAIL SHAPES
eight shapes at one scale · what tells them apart in millimetres
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
STAIN REMOVAL
five stain classes and the method for each — per publication H.E. 2-840 of the University of Kentucky Cooperative Extension
AI MILESTONES
ten tasks, the year of each, the system, the figure — and the human it was measured against
AUDIO FORMATS
who published each standard, when, what it does to the sound, and how many bits per second it allows
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
THE EXIT STATUS
One byte from a command to the shell: what the standard assigns in it, what it leaves to the system — and why “128 + signal number” is nowhere in the standard
FILE DESCRIPTORS
Three levels between a number and a file: what two numbers of one description share, what two descriptions do not — and where the offset lives
FILE LOCKS
A lock lies on a range of bytes, it has two different kinds of owner, and it guards no byte at all
FILE PERMISSIONS
Nine bits in three triads, three special bits — and why r and x on a directory are different powers
![FILENAME EXPANSION: *, ?, […]](/api/img/cmsp2eg3h001q2dpdnyxkt8mu)
FILENAME EXPANSION: *, ?, […]
A leading dot and a slash disappear only in filename expansion: the same pattern “*” is seen by case, but not by expansion itself
HERE-DOCUMENTS
The body reaches the command as a single word, and one quote in the delimiter decides whether it arrives as typed
HTTP STATUS CODES
five classes · twenty codes you meet every day
IFS AND FIELD SPLITTING
Two kinds of delimiter: white ones merge into one, non-white ones each cut on their own — and the same value gives one field or four
LIFE CYCLE MODELS
the same steps arranged five ways: the document, the year, and what one turn of the loop covers
THE MIDI PROTOCOL
one top bit separates status from data, seven commands per channel, and how much time a serial wire actually takes
THE FLAGS OF OPEN()
FIVE flags of creating a file — and why O_CREAT|O_EXCL is not a faster check but a check and a creation joined into one indivisible act
${…}: FOUR MODIFICATIONS
The colon asks about emptiness too: in the column of the empty variable it changes the answer four times out of four, and in the other two columns none
${…}: TRIMMING BY PATTERN
The sign says from which end to cut and doubling it says how much: from the same path the same pair of patterns takes away either one character or fifteen
POSIX SIGNALS
Twenty-seven signals, five default actions — and two that cannot be caught, ignored or blocked
THE ORDER OF REDIRECTIONS
Redirections are done from left to right, and “2>&1” copies where the output points at that very moment: the file first — and it holds two lines; the copy first — one
QUOTING IN THE SHELL
29 characters named by the standard, 4 ways to take the meaning off them — and the 3 characters where double quotes stop
read: A LINE INTO VARIABLES
The last variable takes the whole rest of the line, inner spaces and all; without -r the backslash disappears, and a line with no final newline gives status 1 — although the variable is already full
THE CONDITIONS OF TRAP
FIVE conditions from the standard — EXIT and four signals — and three extensions a conformant shell refuses
THE UMASK
The file mode creation mask: the nine bits it clears, five arguments that name opposite things — and why umask 022 is not chmod 755
VIDEO CARRIERS
nine formats at true scale — and the frame that kept growing after the carrier stopped
VIDEO FORMATS
who published each standard, when, the names it goes by, and what has to be squeezed
WORD EXPANSION
Four steps in a fixed order — and only two of them can change how many fields reach the command
BEER STYLES
colour, bitterness and strength of 15 styles from the BJCP 2021 guidelines
COCKTAIL FORMULAS
five templates by ratio, not fixed recipes — millilitres straight from the official IBA recipes
NINE DRINKS
the same coffee, different proportions
HOW MUCH COFFEE TO WATER
six methods · weight, grind, time
ARABICA AND ROBUSTA
two species, six varieties, one difference