Some unusual loops you will encounter
As you read more C programs written by others,
you'll see some statements that look like for or
while loops, but appear to have something missing.
In fact, any (or all!) of the 3 "parts" of a for loop may be
omitted.
For example, the following loop initially sets i
to 1, and increments it each iteration,
but it doesn't have a "middle" conditional test to see if the loop has finished.
The missing condition constantly evaluates to true:
for(int i = 1 ; /* condition is missing */ ; i = i+1) {
.....
.....
}
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Some loops don't even have a loop-control variable,
and don't test for their termination.
This loop will run forever,
until we interrupt or terminate the operating system process
running the C program.
We term these infinite loops :
// cryptic - avoid this mechanism
for( ; ; ) {
.....
.....
}
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#include <stdbool.h>
// clearer - use this mechanism
while( true ) {
.....
.....
}
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While we often see and write such loops,
we don't usually want them to run forever!
We will typically use an enclosed condition and a break statement
to terminate the loop,
either based on some user input, or the state of some calculation.
CITS2002 Systems Programming, Lecture 2, p17, 24th July 2024.
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CITS2002