Set Specific Bits in a 32-bit Register

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

uint32_t set_bits(uint32_t reg, uint8_t pos, uint8_t len) {
    // step1.1 : define your mask
        // step 1.2 : note that 1 << 32 is underfined so i will do a small check before working 
    uint32_t mask = (len >= 32) ? 0xFFFFFFFF : ((1U << len) - 1) << pos;
	// step 2 : set the delimiter of your mask : (1U << len) 
    // step 3 : flip all the bits before your delimiter but subtracting 1 : ...- 1
	// step 4 : shift you mask with the desired position : << pos 
	// step 5 : apply the mask so it sets the desired bits using the or : 
    return reg | mask;
}

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;
}