C Program to Convert Octal Number to Decimal and vice-versa

#include <stdio.h>
#include <math.h>

// function prototype
long long convertOctalToDecimal(int octalNumber);

int main() {

    int octalNumber;

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

    printf("%d in octal = %lld in decimal", octalNumber, convertOctalToDecimal(octalNumber));

    return 0;
}

// function to convert octalNumber to decimal
long long convertOctalToDecimal(int octalNumber) {
    int decimalNumber = 0, i = 0;

    while(octalNumber != 0) {
        decimalNumber += (octalNumber%10) * pow(8,i);
        ++i;
        octalNumber/=10;
    }

    i = 1;

    return decimalNumber;
}

Output

Enter an octal number: 116
116 in octal = 78 in decimal