A form of programming loop in which the condition for termination (continuation) is computed each time around the loop. There are several variants on this basic idea. For example, Pascal has

• while 〈condition〉 do
• begin
• 〈statements〉
• end
• and also
• repeat
• 〈statements〉
• until 〈condition〉

The first is a while loop and the second is a repeat-until loop. Apart from the obvious difference that the first specifies a continuation condition while the second specifies a termination condition, there is a more significant difference. The while loop is a zero-trip loop, i.e. the body will not be executed at all if the condition is false the first time around. In contrast, the body of a repeat-until loop must be obeyed at least once.

Similar constructs are found in most languages, though there are many syntactic variations. See also do loop.