The function strstr() returns a pointer to the first occurrence of x in a string.
It is also know as searching for a sub-string in a string.

Usage:

char * strstr ( const char *, const char * );
char * strstr ( char * str1, const char * str2 );

Return Value

A pointer to the first occurrence in str1 of any of the entire sequence of characters specified in str2. If nothing is found a null pointer is returned if the sequence is not present in str1.
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Usage of clock():

clock_t clock ( void );

Parameters:

None.

Return Value:

The number of clock ticks elapsed since the program start. If the function fails then it will return a value of -1. The clock_t type is defined in ctime.h.

Explanation:

The function returns the number of clock ticks elapsed since the start of the program. More »

Usage of difftime():

double difftime ( time_t time2, time_t time1 );

Parameters:

Time1 and time2 are both time_t objects.

Return Value:

The difference in seconds between time2-time1 will be returned as a floating point double.

Explanation:

Calculates the difference in seconds between time1 and time2. More »

The null pointer macro (NULL) is generally used to signify that a pointer does not point to an object.

Usage of mktime():

time_t mktime ( struct tm * ptr_time );

Parameters:

The pointer ptr_time points to a tm structure that contains a calendar time, which in turn is broken down into its components.

Return Value:

A time_t value corresponding to the calendar time passed as argument.
If an error occurs then the function mktime() returns a -1 value. More »

Usage of time():

time_t time ( time_t * ptr_time );

Parameters:

ptr_time is a pointer to an object of type time_t. In this object the time value is stored.

It is also allowed to fill in a null pointer, but the a time_t object is still returned by the function time().

Return Value:

The current calendar time as a time_t object. More »

The function mlen() of the library stdlib.h is used to get the length of a multi-byte character.

Usage of mblen():

int mblen ( const char * pmb, size_t max );

The pmb (pointer multibyte character) pointer is pointing to the multi-byte value where you want to know the size of. It will only examine at most max bytes.

Parameters:

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The function mbtowc(), that is part of the stdlib.h library, is used to convert a multi-byte character to wide character.

Usage of mbtowc():

int mbtowc ( wchar_t * pwc, const char * pmb, size_t max );

The multibyte character pointed by pmb (pointer multibyte character) is converted to a wide character which is stored at the location that is pointed by pwc (pointer wide character). The length in bytes of the multiby character is returned. More »

The function qsort() of the stdlib.h is used to sort the elements of an array.

Usage of qsort():

void qsort ( void * base, size_t num, size_t size, int ( * comparator ) ( const void *, const void * ) );

The function qsort() sorts the num element of the array pointed by base. Every element has a size of size bytes long. The qsort function will use the comparator function to determine the order of the elements.

The function will not return a value. The content is modified in the newly sorted order.

Parameters:

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The function bsearch() of the stdlib.h is used to do a binary search in an array.

Usage of bsearch():

void * bsearch ( const void * key, const void * base, size_t num, size_t size, int ( * comparator ) ( const void *, const void * ) );

It is searching for a given key in the array that is pointed to by base. Base is formed by the number of elements (num). Each element has a size of size bytes. The function will return a void* pointer to the first element that is matching the search key. The function compares each element to the key by calling the comparator. More »