20. Clear Specific Bits in a 32-bit Register

#include <stdio.h>
#include <stdint.h>

uint32_t clear_bits(uint32_t reg, uint8_t pos, uint8_t len) {
    uint32_t mask = (1 << len) - 1; // make the mask
    // shift the mask to the required target position
    mask <<= pos;
    // invert the mask and '&' it with reg to get the output
    reg &= ~(mask);
    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;
}