C Program to Convert Octal to Binary using loops and cases

Method 1 – Using loops

#include <stdio.h>
int main()
{
    int OCTALVALUES[] = {0, 1, 10, 11, 100, 101, 110, 111};
    
    long long octal, tempOctal, binary, place;
    
    int rem;
    
    printf("Enter any Octal number: ");
    
    scanf("%lld", &octal);
    
    tempOctal = octal;
    binary = 0;
    
    place  = 1;
    
    while(tempOctal > 0)
    {
        rem = tempOctal % 10;
        
        binary = (OCTALVALUES[rem] * place) + binary;
        tempOctal /= 10;
        
        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

Method 2 – Using Switch Cases

#include <stdio.h>

#define MAX 1000

int main()

{

char octalnum[MAX];

long i = 0;

printf("Enter any octal number: ");

scanf("%s", octalnum);

printf("Equivalent binary value: ");

while (octalnum[i])

{

switch (octalnum[i])

{

case '0':

printf("000"); break;

case '1':

printf("001"); break;

case '2':

printf("010"); break;

case '3':

printf("011"); break;

case '4':

printf("100"); break;

case '5':

printf("101"); break;

case '6':

printf("110"); break;

case '7':

printf("111"); break;

default:

printf("\n Invalid octal digit %c ", octalnum[i]);

return 0;

}

i++;

}

return 0;

Output

Enter any octal number: 160
Equivalent binary value: 001110000