Solving exercise 2-6 setbits() from K&R (The C Programming Language, 2nd Edition) part 1

setbits-pt1.c

/* 2-6 Write a function setbits(x,p,n,y) 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, page 49 */

#include 

unsigned setbits(unsigned x, int p, int n, unsigned y);
unsigned getbits(unsigned x, int p, int n);

int main()
{
    printf("%u\n", setbits(209, 4, 3, 187));
}

/* getbits: get n bits from position p */
unsigned getbits(unsigned x, int p, int n)
{
    return (x >> (p+1-n)) & ~(~0 << n);
}

/* setbits: replace bits p -> p+n of x with rightmost n bits from y */
unsigned setbits(unsigned x, int p, int n, unsigned y)
{
    int bits, result;

    bits = getbits(y, n-1, n);
    /* result = ; */

    return result; 
}