THREE HAND STITCHES
backstitch · running stitch · whipstitch — what shows on the face and what the thread does underneath
STAIN REMOVAL
five stain classes and the method for each — per publication H.E. 2-840 of the University of Kentucky Cooperative Extension
BINARY COUNTING
five doubling cards build every number from 0 to 31 — exactly the way every computer counts
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
GIT WORKING AREAS
four areas · the command that moves code between them
LOGIC GATES
Seven digital-logic symbols — and how to build six of them from a single element, NAND
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
THE CONDITIONS OF TRAP
FIVE conditions from the standard — EXIT and four signals — and three extensions a conformant shell refuses
FIRST FINGER FOODS
the size, the softness and the shape of a piece for a baby who feeds themselves, by the NHS guidance
NEAPOLITAN PIZZA DOUGH
four ingredients in the proportions written into an EU regulation
POUND CAKE
four equal weights — a recipe whose name is its ratio
DIVISIBILITY TESTS
what to read in a written number instead of dividing it: the tail, the digit sum and composite divisors
THE DOOMSDAY RULE
the weekday of any date in the Gregorian calendar, worked out in the head in three steps
THE RULE OF 72
the time it takes steady growth to double: the division you can do in your head, how far it misses and why the divisor is what it is
AMP MIC POSITIONS
where to place a mic in front of a guitar cab and how each spot sounds — after the Shure chart
UKULELE CHORDS
the first twelve chords · standard tuning G C E A
RED CABBAGE pH INDICATOR
the purple juice that changes colour: acid or base, without asking a book
IMPERIAL UNITS
convert in your head · without a calculator
APERTURE, SHUTTER, ISO
one stop is twice the light: three scales with the same step on each
THE RACING LINE
one corner, three apexes, the time computed
TYRE SIZE
what the sidewall marking is made of and what it works out to