Control Flow

By default code runs top to bottom, one statement after another. Control flow is what lets a program choose and repeat instead. Branches (if / else) run one block or another depending on a true/false condition; loops (while, for) run a block over and over until a condition changes.

if temperature > 30
    print "hot"
else
    print "fine"

while fuel > 0
    drive()          repeat until fuel runs out

Every condition ultimately reduces to a boolean, so control flow rests directly on logic — and, or, and not combine conditions exactly as they do in a truth table. Branches and loops are enough, in principle, to express any computation.