Showing posts with label Directive in c. Show all posts
Showing posts with label Directive in c. Show all posts
ifndef in c example
#ifndef, Conditional compilation directives
Syntax:
#if
#else
#endif
#if
#elif
#endif
1.The compiler only compiles the lines that follow the #if directive when evaluates to non-zero.
2.Otherwise, the compiler skips the lines that follow until it encounters the matching #else or #endif.
3.If the expression evaluates to false and there is a matching #else, the lines between the #else and the #endif are compiled.
4.#if directives can be nested, but matching #else and #endif directives must be in the same file as the #if.
5.#elif is like #else except the else block is only compiled if the expression after #elif is non-zero.
Syntax:
#if
#else
#endif
#if
#elif
#endif
1.The compiler only compiles the lines that follow the #if directive when evaluates to non-zero.
2.Otherwise, the compiler skips the lines that follow until it encounters the matching #else or #endif.
3.If the expression evaluates to false and there is a matching #else, the lines between the #else and the #endif are compiled.
4.#if directives can be nested, but matching #else and #endif directives must be in the same file as the #if.
5.#elif is like #else except the else block is only compiled if the expression after #elif is non-zero.
#ifndef
evaluates to 1 if the symbol specified by has not been defined.
Example
#ifndef Quiet PrintDiagnostics(); #endif |
ifdef in c
#ifdef, Conditional compilation directives
Syntax:
#if
#else
#endif
#if
#elif
#endif
1)The compiler only compiles the lines that follow the #if directive when evaluates to non-zero.
2)Otherwise, the compiler skips the lines that follow until it encounters the matching #else or #endif.
3)If the expression evaluates to false and there is a matching #else, the lines between the #else and the #endif are compiled.
4)#if directives can be nested, but matching #else and #endif directives must be in the same file as the #if.
5)#elif is like #else except the else block is only compiled if the expression after #elif is non-zero.
#ifdefevaluates to 1 if the symbol specified by has been previously
defined with a #define directive.
Example
Syntax:
#if
#else
#endif
#if
#elif
#endif
1)The compiler only compiles the lines that follow the #if directive when
2)Otherwise, the compiler skips the lines that follow until it encounters the matching #else or #endif.
3)If the expression evaluates to false and there is a matching #else, the lines between the #else and the #endif are compiled.
4)#if directives can be nested, but matching #else and #endif directives must be in the same file as the #if.
5)#elif is like #else except the else block is only compiled if the expression after #elif is non-zero.
#ifdef
defined with a #define directive.
Example
#ifdef DEBUG printf("Total space %d\n", space); #endif |
if directives
#if directive
Conditional compilation directives
Syntax:
#if
#else
#endif
1)The compiler only compiles the lines that follow the #if directive when
evaluates to non-zero.
2)Otherwise, the compiler skips the lines that follow until it encounters the
matching #else or #endif.
3)If the expression evaluates to false and there is a matching #else, the
lines between the #else and the #endif are compiled.
4)#if directives can be nested, but matching #else and #endif directives must
be in the same file as the #if.
Conditional compilation directives
Syntax:
#if
#else
#endif
1)The compiler only compiles the lines that follow the #if directive when
2)Otherwise, the compiler skips the lines that follow until it encounters the
matching #else or #endif.
3)If the expression evaluates to false and there is a matching #else, the
lines between the #else and the #endif are compiled.
4)#if directives can be nested, but matching #else and #endif directives must
be in the same file as the #if.
Example
#if defined(NEARPOINTERS) space = farcoreleft(); #elif defined(FARPOINTERS) space = coreleft(); #else #error Unsupported memory model #endif |
#error in c
#error (directive)
Issues error message
Syntax:
#error
If this line of code is compiled by the compiler, a fatal error message will be issued for this line and include the text defined by.
Example:
Issues error message
Syntax:
#error
If this line of code is compiled by the compiler, a fatal error message will be issued for this line and include the text defined by
Example:
#if !defined(MODEL) #error Building model not defined #endif |
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