Topic 0 · Programming Fundamentals (Python)

A named box in memory. `x = 25` stores 25; a later `x = 78` replaces it.

`=` stores a value; `==` tests equality.

`//` floor-divides; `% 10` gives the last digit, `// 10` drops it.

Repeat *while* a condition is true: init → test → update, or it never stops.

`for i in range(a, b):` runs i = a … b−1 → b−a times.

Runs the FIRST true branch only; put narrow conditions first.

Track every variable line-by-line — the #1 exam skill.

`loop while … end loop`, `if … then … end if`, `output` — exam answers use this, not Python.

`def avg(a,b,c): return (a+b+c)/3`. Define once, call many.

Parameter = name in the def; argument = value passed in the call.

Sends a value back AND ends the function. `return` ≠ `print`.

A name made inside a function is local — gone when it ends.

Reassigning an int doesn't affect the caller; *mutating* a list does.

`nums = [10,20,30]`; `nums[0]` is 10; `nums[-1]` is the last.

First is index 0; last is `len(nums)-1`.

Track a counter n for used slots; loop `range(n)`, not full length.

`table[r][c]` = row r, column c (both from 0).

Outer rows × inner columns = rows×cols iterations.

Specific input + expected output. Cover normal, boundary, erroneous.

Edges of valid range (0, MAX, empty, full). Off-by-one bugs hide here.

Tests behaviour from outside — only inputs/outputs.

Tests internals — code coverage, every branch.

Reproduce → isolate → hypothesise → fix → re-test (don't skip the last).