IF.HELPREXX

IF instruction

+-----------------------------------------------------------------------------+
| IF [expression][;] THEN[;] instruction [ELSE[;] instruction]                |
+-----------------------------------------------------------------------------+

The IF instruction evaluates the specified expression, which must result in
either 0 or 1.  It the expression result is 1, the instruction specified by
the THEN keyword is executed.  Otherwise, if the ELSE keyword is specified,
its instruction is executed instead.

IF instructions can be nested, and if they are, the ELSE keyword closes the
most recent open IF.  Under certain circumstances, using ELSE NOP may be
necessary to align further ELSEs to the intended IFs.

Examples:

    /* Using indentation to show how IFs and ELSEs are bound */
    if answer='YES'
      then if name='FRED'
             then say 'OK, Fred.'
             else say 'OK.'
      else say 'Why not?