4.34 If Directive

Suggested Replacement

The PIC Assembler's IF directive is a direct replacement for this directive.

The operand must be an absolute expression and if non-zero, then the code following the IF up to the next matching ELSE, ELSIF or ENDIF will be assembled. If the operand is zero, then the code up to the next matching ELSE or ENDIF will not be output. At an ELSE, the sense of the conditional compilation will be inverted, while an ENDIF will terminate the conditional assembly block.

IF DEMO
  call demo_mode
ELSE
  call play_mode
ENDIF

Assembly code in both true and false cases is always scanned and interpreted, but the machine code corresponding to the instructions is output only if the condition matches. This implies that assembler directives (e.g., EQU) will be processed regardless of the state of the condition expression, and so, should not be used inside an IF - ENDIF construct.

Although the MPASM assembler allows you to use a #IF form of this directive, note that it is still an assembler directive. The PIC Assembler's #if directive is a preprocessor directive, hence will be looking at the result of a preprocessor expression (potentially using preprocessor symbols), not an assembler expression (potentially using assembler symbols). If you migrate your code to use the preprocessor directive, ensure that you also examine the expressions involved, defining as required the equivalent preprocessor macros using either the#define directive or -D option.