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 res;
    for(uint8_t i = pos ; i<(pos+len) ;i++)
    {
        res |= 1<<i;
    }
    res = ~res;
    return reg&res;

    /*
    uint32_t mask = (1U << len) - 1U;   //Use this as constant line to generate mask starting from LSB as 1
    mask = mask << pos;
    mask = ~mask;
    return reg&mask;
    */
}

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;
}