Here it goes...

CLOCK
Syntax

#include <time.h>

clock_t clock(void);
Description

This function returns the number of clock ticks since an arbitrary time, actually, since the first call to clock, which itself returns zero. The number of tics per second is CLOCKS_PER_SEC.
Return Value

The number of tics.
Portability

ANSI, POSIX
Example

printf("%d seconds have elapsed\n", clock()/CLOCKS_PER_SEC);

SLEEP
Syntax

#include <unistd.h>

unsigned sleep(unsigned seconds);
Description

This function causes the program to pause for seconds seconds.
Return Value

The number of seconds that haven't passed (i.e. always zero)
Portability

not ANSI, POSIX
Example

sleep(5);