Control Register Using Nested Bitfields

Code

#include <stdio.h>

typedef union {
    unsigned char reg;
    struct {
        unsigned char enable : 1;
        unsigned char mode : 1;
        unsigned char priority : 2;
        unsigned char reserved : 4;
    } bits;
} ControlRegister;

// Write your logic here
int validate_register(ControlRegister *ctrl) {
   /* unsigned char enable = (ctrl->bits.enable) == 1;
    unsigned char priority = (ctrl->bits.priority) <= 2;
    unsigned char reserved = (ctrl->bits.reserved) == 0;*/

    /* ANOHERT SOLUTION BY USING REG ONLY NOT BIT FIELD */
    unsigned char reg = ctrl->reg ;
    unsigned char enable = (reg & 1) == 1;
    unsigned char priority = ((reg >> 2)&3) <= 2;
    unsigned char reserved = (reg & 0xF0) == 0;

    return (enable && priority && reserved) ? 1 : 0;
}

int main() {
    ControlRegister ctrl;
    scanf("%hhx", &ctrl.reg);

    int result = validate_register(&ctrl);
    printf("%d", result);

    return 0;
}

Solving Approach