1. Set or Clear a Specific Bit in a Register

#include <stdio.h>
unsigned char modifyBit(unsigned char reg, int pos, int mode) {
    if(pos>7 || pos<0){
        return -1;
    }
    if (mode == 1){
        // we want to set a bit
        reg |= ((1U) << pos);
        return reg;
    }
    else if (mode ==0){
        // we want to clear a bit
        reg &= ~((1U) << pos);
        return reg;
    }
    else{
        return -1;
    }
}

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