20. Clear Specific Bits in a 32-bit Register

#include <stdio.h>
#include <stdint.h>
int day;
uint32_t clear_bits(uint32_t reg, uint8_t pos, uint8_t len) {
    day = ((1<< (len)) - 1);
    reg &= ~(day << pos);

    return reg;
}

int main() {
    uint32_t reg;
    uint8_t pos, len;
    scanf("%u %hhu %hhu", &reg, &pos, &len);
    printf("%u", clear_bits(reg, pos, len));
    return 0;
}