memcpy function in C language

/* A C program to demonstrate working of memcpy */
#include <stdio.h>
#include <string.h>

int main ()
{
char str1[] = "Geeks";
char str2[] = "Quiz";

puts("str1 before memcpy ");
puts(str1);

/* Copies contents of str2 to sr1 */
memcpy (str1+5, str2, sizeof(str2));

puts("\nstr1 after memcpy ");
puts(str1);

return 0;
}