Returns the positive integer that you get when you reverse the digitsof parameter n

[tousifrad]

#include <iostream>
using namespace std;

int reverse(int n);

int main()
{
    int number;
    int n;

    cout << " Enter number to reverse." << endl;
    cin >> number;
    cout << reverse(number % 10,0);

    return 0;
}//end main

int reverse(int number,int n)
{

    if(n < 10)
    {
        return n;
    }
    else
    {
        return reverse(number/10,n);
    }
}

[weaknessforcats]

You don't say what your question is, but I am guessing it's why this won't compile:

int reverse(int n);
 
int main()
{
etc...

You reverse function has two arguments but your prototype above shows only one argument. When the compiler sees you call reverse with two arguments, it generates a "function does not exist" message.