postal code exchanger

#include <stdio.h>
#include <stdlib.h>

#define TST_BIT(num, bit) ((1 << (bit)) & (num))

const char dig_mask[11][10] =
    {{0x3f, 0x1,  0x3f, 0x3f, 0x21, 0x3f, 0x1,  0x3f, 0x3f, 0x3f},
     {0x21, 0x3,  0x1,  0x2,  0x21, 0x20, 0x2,  0x2,  0x21, 0x21},
     {0x21, 0x5,  0x1,  0x4,  0x21, 0x20, 0x4,  0x4,  0x21, 0x21},
     {0x21, 0x9,  0x1,  0x8,  0x21, 0x20, 0x8,  0x8,  0x21, 0x21},
     {0x21, 0x11, 0x1,  0x10, 0x21, 0x20, 0x10, 0x10, 0x21, 0x21},
     {0x21, 0x21, 0x1,  0x3f, 0x3f, 0x3f, 0x3f, 0x20, 0x3f, 0x3f},
     {0x21, 0x1,  0x2,  0x2,  0x1,  0x1,  0x21, 0x20, 0x21, 0x2 },
     {0x21, 0x1,  0x4,  0x4,  0x1,  0x1,  0x21, 0x20, 0x21, 0x4 },
     {0x21, 0x1,  0x8,  0x8,  0x1,  0x1,  0x21, 0x20, 0x21, 0x8 },
     {0x21, 0x1,  0x10, 0x10, 0x1,  0x1,  0x21, 0x20, 0x21, 0x10},
     {0x3f, 0x1,  0x3f, 0x20, 0x1,  0x3f, 0x3f, 0x20, 0x3f, 0x20}};

void print_digits(const char *digits);

int main (void)
{
    char postal_code[6] = {0};

    printf("Enter a postal code: ");
    scanf("%6s", postal_code);
    printf("\n\n");
    print_digits(postal_code);

    system("pause > nul");
    return 0;
}

void print_digits(const char *digits)
{
    int i, j, z;
    for (j = 0; j < 11; j++)
    {
        for (z = 0; digits[z]; z++)
        {
            for (i = 5; i >= 0; i--)
                printf("%c", TST_BIT(dig_mask[j][digits[z] - 48], i) ? 0xf9 : ' ');
            printf("  ");
        }
        putchar('\n');
    }
}