Question

How to replace a bit of an integer at a specified position from another integer in C

Answer 1

#include <stdio.h>

void print_bits(int n, int size) {
    for (int i = 1 << (size - 1); i > 0; i = i / 2) {
        (n & i) ? printf("1") : printf("0");
    }
}


int main() {

    int a = 15, b = 10, pos = 2; // form right

    print_bits(a, 4);
    printf("\n");

    print_bits(b, 4);
    printf("\n");

    int bit_at_pos = (b >> pos) & 1;
    printf("bit_at_pos = %d\n", bit_at_pos);

    if (bit_at_pos == 1) {
        bit_at_pos = bit_at_pos << pos;
        a |= bit_at_pos;
    }
    else {
        int flag = 255; // FF = 11111111
        bit_at_pos = 1 << pos;
        flag = flag ^ bit_at_pos;
        a &= flag;
    }

    printf("a = %d\n", a);
    print_bits(a, 4);

    return 0;
}




/*
run:

1111
1010
bit_at_pos = 0
a = 11
1011

*/

 

70+ SQL courses for beginners and professionals