void * memset ( void * ptr, int value, size_t num );
Fill block of memory
Sets the first num bytes of the block of memory pointed by ptr to the specified value (interpreted as an unsigned char).
#include <stdio.h>
#include <string.h>
int main ()
{
char str[] = "almost every programmer should know memset!";
memset (str,'-',8);
puts (str);
return 0;
}