Includes another source file into the current source file at the line immediately after the directive. Syntax #include <filename> (1) #include "filename" (2) Explanation Includes source file, identified by filename, into the current source file at the line immediately after the directive. The first version of the directive searches only standard include directories. The standard C++ library, as well as standard C library, is implicitly included in standard include dire

Defined in header <stdio.h> int rename( const char *old_filename, const char *new_filename ); Changes the filename of a file. The file is identified by character string pointed to by old_filename. The new filename is identified by character string pointed to by new_filename. If new_filename exists, the behavior is implementation-defined. Parameters old_filename - pointer to a null-terminated string containing the path identifying the file to rename new_filename

An object whose identifier is declared without the storage-class specifier _Thread_local, and either with external or internal linkage or with the storage-class specifier static, has static storage duration. Its lifetime is the entire execution of the program and its stored value is initialized only once, prior to program startup. Notes Since its stored value is initialized only once, an object with static storage duration can profile the invocations of a function. The other use of the keywo

Defined in header <time.h> double difftime( time_t time_end, time_t time_beg ); Computes difference between two calendar times as time_t objects (time_end - time_beg) in seconds. If time_end refers to time point before time_beg then the result is negative. Parameters time_beg, time_end - times to compare Return value Difference between two times in seconds. Notes On POSIX systems, time_t is measured in seconds, and difftime is equivalent to arithmetic subtr

Defined in header <stdlib.h> void abort(); Causes abnormal program termination unless SIGABRT is being caught by a signal handler passed to signal and the handler does not return. Functions passed to atexit() are not called. Whether open resources such as files are closed is implementation defined. Implementation defined status is returned to the host environment that indicates unsuccessful execution. Parameters (none). Return value (none). Example #include <s

Defined in header <complex.h> float complex CMPLXF( float real, float imag ); (since C11) double complex CMPLX( double real, double imag ); (since C11) long double complex CMPLXL( long double real, long double imag ); (since C11) Each of these macros expands to an expression that evaluates to the value of the specified complex type, with the real part having the value of real (converted to the specified argument type) and the imaginary part having the

Defined in header <complex.h> #define imaginary _Imaginary (since C99) This macro expands to the keyword _Imaginary. This is a convenience macro that makes it possible to use float imaginary, double imaginary, and long double imaginary as an alternative way to write the three pure imaginary C types float _Imaginary, double _Imaginary, and long double _Imaginary. As with any pure imaginary number support in C, this macro is only defined if the imaginary numbers are supported

The preprocessor is executed at translation phase 4, before the compilation. The result of preprocessing is single file which is then passed to the actual compiler. Directives The preprocessing directives control the behavior of the preprocessor. Each directive occupies one line and has the following format: # character preprocessing instruction (one of define, undef, include, if, ifdef, ifndef, else, elif, endif, line, error, pragma) [1] arguments (depends on the instruction) line bre

This is a list of reserved keywords in C. Since they are used by the language, these keywords are not available for re-definition. autobreakcasecharconstcontinuedefaultdodoubleelseenumextern. floatforgotoifinline (since C99)intlongregisterrestrict (since C99)returnshort. signedsizeofstaticstructswitchtypedefunionunsignedvoidvolatilewhile. _Alignas (since C11)_Alignof (since C11)_Atomic (since C11)_Bool (since C99)_Complex (since C99)_Generic (since C11)_Imaginary (since C99)_Noreturn (si

Defined in header <stdlib.h> int atoi( const char *str ); long atol( const char *str ); long long atoll( const char *str ); (since C99) Interprets an integer value in a byte string pointed to by str. Discards any whitespace characters until the first non-whitespace character is found, then takes as many characters as possible to form a valid integer number representation and converts them to an integer value. The valid integer value consists of the fo