1. Set or Clear a Specific Bit in a Register

#include <stdio.h>

#define SHIFT(n) (1 << n) 
unsigned char modifyBit(unsigned char reg, int pos, int mode) {
    if (mode){ 
        reg |= (SHIFT(pos)); 
    }
    else { 
        //clear the bit 
        reg &= ~(SHIFT(pos)); 
    }
    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;
}