The #if directive can be used to test whether an expression evaluates to a nonzero value or not. If the result of the expression is nonzero, then subsequent lines upto a #else, #elif or #endif are compiled, otherwise they are skipped.
Syntax of #if directive as:
#if LABEL == 10
statement 1;
statement 2;
#else
statement 3;
statement 4;
statement 5;
#endif
If we so desire, we can have nested conditional compilation directives.
Sometimes, it may be desirable to cause a defined name to become 'undefined'. This can be accmplished by means of the #undef directive.
Syntax: #undef macro_temp_name
example: #undef TEST
This is a special directive that we use to turn on or off certain features. Pragma vary from one compiler to another.
Turbo c/c++ compiler has got a pragma that allows you to suppress warnings generated by the compiler.
Some pragmas directives as following:
Syntax of #if directive as:
#if LABEL == 10
statement 1;
statement 2;
#else
statement 3;
statement 4;
statement 5;
#endif
If we so desire, we can have nested conditional compilation directives.
#undef directive
Sometimes, it may be desirable to cause a defined name to become 'undefined'. This can be accmplished by means of the #undef directive.
Syntax: #undef macro_temp_name
example: #undef TEST
#pragma Directive
This is a special directive that we use to turn on or off certain features. Pragma vary from one compiler to another.
Turbo c/c++ compiler has got a pragma that allows you to suppress warnings generated by the compiler.
Some pragmas directives as following:
- #pragma startup and #pragma exit
- #pragma warn
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