CC78K0S Datasheet, PDF (146/520 Pages) NEC – C Compiler Ver.1.30 or Later Language

CHAPTER 9 PREPROCESSING DIRECTIVES (COMPILER DIRECTIVES)
(4) #ifndef directive
Conditional Inclusion
#ifndef
FUNCTION
The #ifndef directive is equivalent to:
#if !defined (identifier)
If the identifier has never been defined with the #define directive, the source code between #ifndef and #endif
will not be translated.
SYNTAX
#ifndef identifier new-line group
EXAMPLE
#define ON
#ifndef ON
.
.
.
#endif
EXPLANATION
In the above example, the identifier “ON” has been defined with the #define directive. Thus, the program
between #ifndef and #endif will not be translated. If the identifier “ON” has never been defined, the program
between #ifndef and #endif will be translated.
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User’s Manual U14872EJ1V0UM