Control structures

Repeating, traversing, choosing among many — everything that decides the order of statements.

The previous section gave the program a choice between two paths. It still cannot do a thing several times — and until it can, every repetition has to be written out by hand.

This section gathers what commands the order of execution: repeating while a condition holds, counting, traversing a sequence of values, and choosing among several cases at once.

In this section

• 4.1While loop

  while, do/while, and the one thing that keeps a loop from running forever.

• 4.2For loop

  The three clauses of for, the scope of its variable, and the two words that cut it short.

• 4.3For in loop

  A sequence of values, and the loop that takes them one at a time, with no index or counter.

• 4.4Switch case

  One value, some cases, a default — and what it works on.