HLASM Language Reference

SETB Instruction
Logical (SETB) Expressions
You can use a logical expression to assign a binary value to a SETB symbol. You
can also use a logical expression to represent the condition test in an AIF
instruction. This use lets you code a logical expression whose value (0 or 1) varies
according to the values substituted into the expression and thereby determine
whether or not a branch is to be taken.
Figure 101 on page 364 defines a logical expression.
It is important to note that logical expressions contain unquoted spaces that do not
terminate the operand field. This is called “logical-expression format,” and such
expressions are always enclosed in parentheses.
A logical expression can consist of a logical expression and a logical term
separated by a logical operator delimited by spaces. The logical operators are:
AND
Format: Logical-expression
Operands: Binary
Output: (aexpr1 AND aexpr2) has value 1, if each logical expression
evaluates to 1, otherwise the value is 0.
Example
After the following statements &VAR contains the arithmetic value .
Name Operation Operand
&OP1 SETB 1
&OP2 SETB
&VAR SETB (&OP1 AND &OP2)
AND NOT
| ISBIN
Format: Logical-expression
Operands: Binary
Output: The value of the second logical term is inverted, and the expression
is evaluated as though the AND operator was specified.
Example
(1 AND NOT ) is equivalent to (1 AND 1).
| Format: Function-invocation
| Operands: Character
| Output: ISBIN('cexpr') determines the validity of cexpr, a string of 1 to 32
| characters, as the nominal value of a binary self-defining term usable in a
| SETA expression. If valid, ISBIN returns 1; otherwise, it returns zero. The
| argument string may not be null.
| Example
| ISBIN('111') returns 1
| ISBIN('11111111111111111') returns (excess digits)
| ISBIN('12121') returns (non-binary digits)
| ISBIN('') indicates an error condition
Chapter 9. How to Write Conditional Assembly Instructions 365