Extract a Bit Field from a 32-bit Register

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#include <stdio.h>
#include <stdint.h>
 
uint32_t extract_field(uint32_t reg, uint8_t pos, uint8_t len) {
    // Your code here
   
    uint32_t temp = reg>>pos;
    uint32_t num = 0;
 
 for(int i=0; i<len; i++)
 {
    num = num|1;
    num = num<<1;
 }
    num = num >>1;
 
    return temp&num;
}
 
int main() {
    uint32_t reg;
    uint8_t pos, len;
    scanf("%u %hhu %hhu", &reg, &pos, &len);
    printf("%u", extract_field(reg, pos, len));
    return 0;
}