6.1.9.44 Set Directive

The SET directive is equivalent to EQU (Equ Directive), except that it allows a symbol to be re-defined in the same module without error. For example:

thomas SET 0h
; code using first value
thomas SET 44h
;code using second value

will equate the symbol thomas to the value 0, then later in the program, equate the same symbol to the different value 0x44.

This directive performs a similar function to that of the preprocessor’s #define directive (see Preprocessor Directives), which is often preferred in assembly programs to represent values with symbols.

Note that this directive does not create variables. It does not reserve any memory for the symbol created. Use the DS directive to reserve data memory associated with a label (see Ds Directive).

As there can be more than one local symbol in separate assembly modules with the same name, only SET symbols that are marked as being globally accessible (See Global Directive) will be visible when debugging. For example, in the following code:

GLOBAL mode
mode SET 2

the mode symbol will be watchable in IDEs.

Since SET directives do not contribute to the output, they are processed separately to other instructions and directives. Thus, the program location counter cannot be used in SET operand expressions.