The WHILE and WEND verbs work together to create a program loop:
1000 WHILE A<B
WHILE/WEND constructs can be used alone on lines or within compound
The loop repeats as long as the WHILE condition is true. If the WHILE condition is initially false, the loop is skipped. Multiple WHILE .. WEND loops may be nested.
Because WHILE .. WEND uses the same stack as FOR .. NEXT and GOSUB, active WHILE .. WEND loops must use an EXITTO verb to exit, similar to jumping out of FOR .. NEXT loops.
PRO/5 also supports the looping construct REPEAT .. UNTIL.