Pascal: Difference between REPEAT..UNTIL and WHILE..DO

Pascal supports two forms of conditional loop: REPEAT..UNTIL and WHILE..DO.
A loop of the form

REPEAT
UNTIL <condition>

will be executed at least once, even if the condition is satisfied before the
first execution.

The loop consisting of

WHILE <condition> DO

will be executed ONLY if the condition is satisfied when the loop is entered.
For further information, see pages 22 and 23 of the Pascal User Manual and
Report.