1. Set or Clear a Specific Bit in a Register

#include <stdio.h>

#define SET_BIT(reg,pos)   ((reg) |= (1 << pos))
#define CLEAR_BIT(reg,pos) ((reg) &= ~(1 << pos))

unsigned char modifyBit(unsigned char reg, int pos, int mode) 
{
    if(mode)
        SET_BIT(reg, pos);
    else
        CLEAR_BIT(reg, 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;
}