IF1              Assemble If Pass 1                            MASM Directive

  IF1
  statements
  [ELSE
  statements]
  ENDIF

    Initiates a conditional block, causing assembly of the statements up
    to the optional ELSE directive, provided the current assembly pass is
    Pass 1.

       Notes:     IF1 tests only for the current assembly pass, and
                  therefore takes no expression argument.