77. Validate Configuration Register Layout

#include <stdio.h>

typedef struct {
    unsigned short reg;
} ConfigRegister;

int validate_config(ConfigRegister *cfg) {
    // Write logic using pointer access
    return (cfg->reg & 0x01) && !(0x03 == (cfg->reg >> 2) & 0x03) && !(cfg->reg & 0xfff0);
}

int main() {
    ConfigRegister cfg;
    scanf("%hx", &cfg.reg);

    int result = validate_config(&cfg);
    printf("%d", result);

    return 0;
}

Alternate soultion is more concise and easier to understand

int validate_config(ConfigRegister *cfg) {
    unsigned short val = cfg->reg;

    int enable = val & 0x0001;
    int priority = (val >> 2) & 0x03;
    int reserved_clear = (val & 0xFFF0) == 0;

    return (enable && priority != 0x03 && reserved_clear);
}