C+ + Tutorial: how to do input validation using while loops.

I demonstrate how to perform input validation in C++ using a while loop. This is a tutorial for beginners introducing the topic as covered in our textbook.

In other words, we're going to check user input with a while loop.

2:18 ⇒ Theory
3:39 ⇒ Get to the code

Here's the basic algorithm:

Ask for some input
while the input is something we don't like:
Tell the user there something wrong
Ask for the input again

Continue on with the rest of the program

We'll cover the logic, write a sample program, and see what happens if you use if (bad) instead of while (good), a common mistake made by new students. Sample programs are written using Visual Studio 2022.

// Learn More //
C++ Playlist:

while loops:

// Consider supporting this channel in multiple ways
Bitcoin: 177wfkQwzXiC8o2whQMVpSyuWUs95krKYB

[jakedodge]

Thank you so much, Hank. I was ignorantly trapping my entire if/else if/else code inside the loop WITH the small part I needed looped... until I found your video. Can't tell you how relieved I am to get past this part. Appreciate the step by step instruction. Very easy to understand now!

[faizaniftikhar]

i think it was a good example to show use of do while loop here

[sebastianviecco]

Could we do something like this to save some memory or just save some lines of code? Or is this less efficient?

#include <iostream>
using namespace std;

int main()
{
int number = -1;

while (number <= 0)
{
cout << "Enter a positive number: ";
cin >> number;

if (number <= 0)
{
cout << "Input must be positive. Try again!\n";
}
}

cout << "The number you entered: " << number << "\n";

cin.ignore();
cin.get();
return 0;
}