Set or Clear a Specific Bit in a Register

Code

#include <stdio.h>

#define BITS_IN_BYTE (8)// can be replaced by CHAR_BIT from limits.h
// helper macro to derive max bit position given the datatype
#define MAX_BIT_POS(x)  ( (sizeof(x) * BITS_IN_BYTE) - 1 )

// function allowe mods
typedef enum mode_func{
    MODE_CLR =0,// clear bit
    MODE_SET =1// set bit
} mode_func_t;

// function return status
typedef enum status_mod{
    STATUS_NO_ERROR =0,// operation complete
    STATUS_INVALID_POS =1,// invalid bit position
    STATUS_INVALID_MOD =2// invalid function mode
} status_mod_t;

char *status_msg_arr[] = { 
    "success", 
    "invalid position", 
    "invalid mode" };

// function to modify bit at specified position 
status_mod_t modifyBit(unsigned char *reg, int pos, mode_func_t mode) {

    // check pos for valid value
    if (pos>MAX_BIT_POS(*reg)) {return STATUS_INVALID_POS;}
    switch (mode){
        case MODE_CLR:
            *reg &= ~(1<<pos);
            break;
        case MODE_SET:
            *reg |= (1<<pos);
            break;
        default:
            return STATUS_INVALID_MOD;
    }
    return STATUS_NO_ERROR;
}

int main() {
    unsigned char reg;
    int pos;
    mode_func_t mode;
    scanf("%hhu %d %d", &reg, &pos, &mode);
    status_mod_t status = modifyBit(&reg, pos, mode);
    if (status == STATUS_NO_ERROR){
        printf("%d", reg);
    }
    else{
        printf(" error: %s!",status_msg_arr[status]);        
    }
    return 0;
}

Solving Approach