C 程序 八进制转换为二进制

#include <stdio.h>
#include <math.h>
//This function converts octal number to binary number
long octalToBinary(int octalnum)
{
    int decimalnum = 0, i = 0;
    long binarynum = 0;

    /* This loop converts octal number "octalnum" to the
     * decimal number "decimalnum"
     */
    while(octalnum != 0)
    {
    decimalnum = decimalnum + (octalnum%10) * pow(8,i);
    i++;
    octalnum = octalnum / 10;
    }

    //i is re-initialized
    i = 1;

    /* This loop converts the decimal number "decimalnum" to the binary
     * number "binarynum"
     */
    while (decimalnum != 0)
    {
    binarynum = binarynum + (decimalnum % 2) * i;
    decimalnum = decimalnum / 2;
    i = i * 10;
    }

    //Returning the binary number that we got from octal number
    return binarynum;
}
int main()
{
    int octalnum;

    printf("Enter an octal number: ");
    scanf("%d", &octalnum);

    //Calling the function octaltoBinary
    printf("Equivalent binary number is: %ld", octalToBinary(octalnum));

    return 0;
}

Enter an octal number: 71
Equivalent binary number is: 111001