1. Set or Clear a Specific Bit in a Register

#include <stdio.h>

unsigned char modifyBit(unsigned char reg, int pos, int mode) {
    unsigned char mask = 0x01;
    if(pos > 7) { return 0; }
    if(mode != 0 && mode != 1) {return 0; }

    mask = mask << pos;
    if(mode == 1){
        reg |= mask;
    } else if(mode == 0){
        mask = ~mask;
        reg &= mask;
    }

    return reg;
}

int main() {
    unsigned char reg;
    int pos, mode;
    scanf("%hhu %d %d", &reg, &pos, &mode);
    printf("%d", modifyBit(reg, pos, mode));
    return 0;
}