MARS
size, distances and time — computed from rotation, orbit and mass
THREE HAND STITCHES
backstitch · running stitch · whipstitch — what shows on the face and what the thread does underneath
SIZE CHARTS
shoes, tops, bottoms — and a centimetre under every grid
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
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
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
A NUMBER IN 32 BITS
sign, exponent and significand: what actually sits in a float and what does not
GIT WORKING AREAS
four areas · the command that moves code between them
IPv6 ADDRESS NOTATION
eight groups of sixteen bits, the double colon, and one canonical spelling out of thousands
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 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
${…}: 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
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
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
THE CONDITIONS OF TRAP
FIVE conditions from the standard — EXIT and four signals — and three extensions a conformant shell refuses
ENGLISH PUNCTUATION
twelve marks and the three strokes: a name, a job and one working example for each
THE COLLATZ CONJECTURE
halve the even, triple the odd and add one: the road of 27, the record holders and a problem nobody has solved
THE DOOMSDAY RULE
the weekday of any date in the Gregorian calendar, worked out in the head in three steps