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#define - Define a preprocessor macro.
#define MAX 256 #define ERROR_STR "\pError, try again." #define MAX(A,B) ( (A)>(B) ? (A) : (B) )
#undef - Remove a preprocessor macro definition.
#undef MAX
#include - Insert text from another source file.
#include <file> ->searches 'standard' locations #include "file" ->searches 'local' locations
#if - Conditionally include some text, based on the value of a constant expression.
#if MAX > 256 #include "altSize.h" #endif
#ifdef - Conditionally include some text, based on whether a macro name is defined.
#ifndef - Conditionally include some text, based on whether a macro name is not defined.
#ifndef MAX #define MAX 256 #endif
#else - Alternatively include some text, if the previous #if, #ifdef, #ifndef, or #elif test failed.
#endif - Terminate conditional text.
#line - Supply a line number for compiler messages.
#elif - Alternatively include some text based on the value of another constant expression, if the previous #if, #ifdef, #ifndef, or #elif test failed.
#ifndef OS #define OS MAC #endif #if OS == MAC #define SYS_HEADER "MacOS.h" #elif OS == WIN95 #define SYS_HEADER "Win95.h" #elif OS == UNIX #define SYS_HEADER "Unix.h" #endif
defined - Preprocessor function that yields 1 if a name is defined as a preprocessor macro and 0 otherwise; used in #if and #elif statements.
#if defined TOKEN -or- #if defined(TOKEN)
unary # - Operator to replace macro parameter with a string constant containing the parameter's value.
#define PRINT(a) printf( "value = " #a "\n") 'PRINT(5);' becomes 'printf("value = 5\n");'
binary ## - Operator to create a single token out of two adjacent tokens.
#define INPUT(i) input ## i 'INPUT(1) = INPUT(2);' becomes 'temp1 = temp2;'
#pragma - Specify implementation-dependent information to the compiler.
#error - Produce a compile-time error with a designated message.
#error "Opps! MAX not Defined."
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