Memset is used to set a buffer with a specific character
 for example
memset (dptr, 'A', 10); // sets the first 10 character to character 'A'

#include <memory.h>
#include <stdio.h>

int main( void )
{
   char buffer[] = "This is a test of the memset function";

   printf( "Before: %sn", buffer );
   memset( buffer, '*', 4 );
   printf( "After:  %sn", buffer );
}

Output
Before: This is a test of the memset function
After:  **** is a test of the memset function