C Program to Convert Octal Number to Decimal

 program:

#include <stdio.h>
#include <math.h>
long long con(int octalNum);
int main()
 {
 int octalNum;
 printf("Enter an octal number: ");
 scanf("%d", &octalNum);
 printf("%d in octal = %lld in decimal", octalNum, con(octalNum));
 return 0;
 }
 long long con(int octalNum)
 {
 int decimalNum = 0, i = 0;
 while(octalNum != 0)
 {
 decimalNum += (octalNum%10) * pow(8,i);
 ++i;
 octalNum/=10;
 }
 i = 1;
 return decimalNum;
 }

output: