Set Specific Bits in a 32-bit Register

Code

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

uint32_t set_bits(uint32_t reg, uint8_t pos, uint8_t len) {
    // Your code here
    uint32_t mask = (1U << len) - 1;
    mask = mask << pos;
    return reg | mask;
    /*In a signed integer, the leftmost bit is the "sign bit". 
    Shifting into it can cause problems.Unsigned integers don't have a sign bit,
     so all 32 bits can be used freely.*/
}

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

Solving Approach