C program that returns x with the n bits that begin at position p set to the rightmost n bits of y, leaving the other bits unchanged.

Setbits

#include <stdio.h>

unsigned setbits(unsigned x, int p, int n, unsigned y);
int main()
{
	printf("%d", setbits(17, 4, 3, 13));
	return 0;
}
unsigned setbits(unsigned x, int p, int n, unsigned y)
{
	return(((y & ~(~0 << n)) << (p + 1 - n)) | (x & ~((~(~0 << n) << (p + 1 - n)))));
}