C program to convert Octal to Binary number system

Example

Input

Input octal number: 172

Output

Binary of 172: 01111010

Logic to convert octal to binary number system

I have divided the octal to binary conversion in three steps.

1. Extract last digit from octal number.
2. Find binary equivalent of octal digit found above.
3. Combine all converted binary together.

Octal to Binary conversion table

Decimal	Octal	Binary
0	0	000
1	1	001
2	2	010
3	3	011
4	4	100
5	5	101
6	6	110
7	7	111

/**
 * C program to convert Octal number system to Binary number system
 */

#include <stdio.h>

int main()
{
    int OCTALVALUES[] = {0, 1, 10, 11, 100, 101, 110, 111};
    long long octal, tempOctal, binary, place;
    int rem;
    
    /* Input Octal number from user */
    printf("Enter any Octal number: ");
    scanf("%lld", &octal);
    tempOctal = octal;

    binary = 0;
    place  = 1;
    
    /* Convert octal to binary */
    while(tempOctal > 0)
    {
        /* Extract the last digit of octal */
        rem = tempOctal % 10;

        /*
         * Get the binary equivalent of octal digit
         * add it to the binary variable
         */
        binary = (OCTALVALUES[rem] * place) + binary;

        /* Remove the last octal digit */
        tempOctal /= 10;

        /* Increase the place value */
        place *= 1000;
    }

    printf("Octal number = %lld\n", octal);
    printf("Binary number = %lld", binary);

    return 0;
}

/*
Output :

Enter any Octal number: 1720
Octal number = 1720
Binary number = 1111010000
*/