77. Validate Configuration Register Layout

#include <stdio.h>

typedef struct {
    unsigned short reg;
} ConfigRegister;

int validate_config(ConfigRegister *cfg)
{
    unsigned short value = cfg->reg;   // pointer access

    /* Bit 0 must be 1 (Enable ON) */
    if ((value & (1 << 0)) == 0)
        return 0;

    /* Bits 2–3 (Priority) must NOT be 11 */
    unsigned short priority = (value >> 2) & 0x3;
    if (priority == 3)
        return 0;

    /* Bits 4–15 must all be 0 */
    if ((value & 0xFFF0) != 0)
        return 0;

    return 1;   // valid configuration
}


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

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

    return 0;
}