21. Replace Bit Field in a 32-bit Register

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

uint32_t replace_field(uint32_t reg, uint32_t val, uint8_t pos, uint8_t len) {
    
    uint32_t mask = ~((1<<len)-1 << pos); //4,4    ~(00010000 -1) << 4 ;  ~(0000 1111 << pos); 1111 0000  << 4; 0000 1111 
        val <<= pos;
        reg&= mask;
        reg|=val;
    return reg;

    
}

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