o  The assembler displays an error message if the following
       directives occur outside a conditional assembly block: .ENDC,
       .ELSE, .IF_FALSE, .IF_TRUE, .IF_TRUE_FALSE.

    o  MACRO-64 permits a nesting depth of 100 conditional assembly
       levels. If a statement attempts to exceed this nesting level
       depth, the assembler displays an error message.

    o  The effect of logical expressions can only be achieved by
       using several levels of .IF directives. See Example 5.

    o  Lowercase string arguments are converted to uppercase before
       being compared, unless the string is surrounded by double
       quotes or /NAMES=AS_IS is specified on the command line.

    o  The assembler displays an error message if .IF specifies any
       of the following: a condition test other than those which are
       valid, an illegal argument, or a null argument specified in an
       .IF directive.