as: If

1 
1 7.42 '.if ABSOLUTE EXPRESSION'
1 ==============================
1 
1 '.if' marks the beginning of a section of code which is only considered
1 part of the source program being assembled if the argument (which must
1 be an ABSOLUTE EXPRESSION) is non-zero.  The end of the conditional
1 section of code must be marked by '.endif' (⇒'.endif' Endif.);
1 optionally, you may include code for the alternative condition, flagged
1 by '.else' (⇒'.else' Else.).  If you have several conditions to
1 check, '.elseif' may be used to avoid nesting blocks if/else within each
1 subsequent '.else' block.
1 
1    The following variants of '.if' are also supported:
1 '.ifdef SYMBOL'
1      Assembles the following section of code if the specified SYMBOL has
1      been defined.  Note a symbol which has been referenced but not yet
1      defined is considered to be undefined.
1 
1 '.ifb TEXT'
1      Assembles the following section of code if the operand is blank
1      (empty).
1 
1 '.ifc STRING1,STRING2'
1      Assembles the following section of code if the two strings are the
1      same.  The strings may be optionally quoted with single quotes.  If
1      they are not quoted, the first string stops at the first comma, and
1      the second string stops at the end of the line.  Strings which
1      contain whitespace should be quoted.  The string comparison is case
1      sensitive.
1 
1 '.ifeq ABSOLUTE EXPRESSION'
1      Assembles the following section of code if the argument is zero.
1 
1 '.ifeqs STRING1,STRING2'
1      Another form of '.ifc'.  The strings must be quoted using double
1      quotes.
1 
1 '.ifge ABSOLUTE EXPRESSION'
1      Assembles the following section of code if the argument is greater
1      than or equal to zero.
1 
1 '.ifgt ABSOLUTE EXPRESSION'
1      Assembles the following section of code if the argument is greater
1      than zero.
1 
1 '.ifle ABSOLUTE EXPRESSION'
1      Assembles the following section of code if the argument is less
1      than or equal to zero.
1 
1 '.iflt ABSOLUTE EXPRESSION'
1      Assembles the following section of code if the argument is less
1      than zero.
1 
1 '.ifnb TEXT'
1      Like '.ifb', but the sense of the test is reversed: this assembles
1      the following section of code if the operand is non-blank
1      (non-empty).
1 
1 '.ifnc STRING1,STRING2.'
1      Like '.ifc', but the sense of the test is reversed: this assembles
1      the following section of code if the two strings are not the same.
1 
1 '.ifndef SYMBOL'
1 '.ifnotdef SYMBOL'
1      Assembles the following section of code if the specified SYMBOL has
1      not been defined.  Both spelling variants are equivalent.  Note a
1      symbol which has been referenced but not yet defined is considered
1      to be undefined.
1 
1 '.ifne ABSOLUTE EXPRESSION'
1      Assembles the following section of code if the argument is not
1      equal to zero (in other words, this is equivalent to '.if').
1 
1 '.ifnes STRING1,STRING2'
1      Like '.ifeqs', but the sense of the test is reversed: this
1      assembles the following section of code if the two strings are not
1      the same.
1