Set or Clear a Specific Bit in a Register

Code

#include <stdio.h>
#include<math.h>
unsigned char modifyBit(unsigned char reg, int pos, int mode) {
    // Write your code here
    int k,y[9],j,i=0,sum=0,x;
    k=(int)reg;
    while (k>0)
	{
		x=k%2;
		k=k/2;
		y[i]=x;
		i++;
	}
	for (j=i;j<8;j++)
	{
		y[j]=0;
	}
    if (y[pos]==mode)
    {
        return (int)reg;
    }
    else
    {
        y[pos]=mode;
        for (i=0;i<8;i++)
        {
            sum += y[i] * (1 << i);
        }
        return sum;
    }
    
}

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

Solving Approach