1. Set or Clear a Specific Bit in a Register

#include <stdio.h>

unsigned char modify_bit(unsigned char bit, int pos, int mode){
    // mode: 0-clear, 1-set
    if(mode == 0){
      bit = bit & ~(1 << pos);
    }
    else{
      bit = bit | (1 << pos); 
    }
    return bit; 
}

int main(){
  unsigned char bit; 
  int pos,mode ; 
  scanf("%hhu %d %d",&bit,&pos,&mode); 
  printf("%hhu",modify_bit(bit,pos,mode));

  return 0;
}