The loop construct found in nearly all imperative programming languages which executes one or more instructions (the "loop body") repeatedly so long as some condition evaluates to true. In contrast to a repeat loop, the loop body will not be executed at all if the condition is false on entry to the while.

For example, in c, a while loop is written

        while (<expr>) <statement>;

where is any expression and is any statement, including a compound statement within braces

"..".