Why doesn't the do.. While loop end?

Question

1.00/5 (1 vote)

See more:

Why the do..while loop in this code doesn't end when I enter password1 or password2 or password3? It keeps outputting "access denied".

C++

#include <iostream> 
using namespace std;

int main() {
    
    const string password1 = "peace"; 
    const string password2 = "war";
    const string password3 = "neutral";
    string userpassword;
    
    bool renew = ((userpassword != password1) || (userpassword != password2)|| (userpassword != password3));
    
    do {
        cout << "Enter your password > " << flush;
        cin >> userpassword;
        if (renew) {
            cout << "Access denied" << endl;
        }
    } while (renew);
    
    cout << "correct password" << endl;
    return 0;
}

What I have tried:

I have tried to declare renew in do function but it didn't work out

Posted 25-Nov-20 6:20am

Bassel Mohamed

Updated 25-Nov-20 23:19pm

Add a Solution

4 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Marc Clifton · Answer 1 · 2020-11-25T06:23:00

Solution 1

Because you're never update renew in the do block.

Posted 25-Nov-20 6:23am

Marc Clifton

Comments

Bassel Mohamed 25-Nov-20 12:26pm

More clarification please

jeron1 25-Nov-20 12:28pm

you set renew before entering the do-while loop, never change it inside the do-while loop. You're testing something in the while statement that is unchanging.

Bassel Mohamed 25-Nov-20 12:31pm

can you type the correct code please?

Rick York 25-Nov-20 12:32pm

Can't you?

Bassel Mohamed 25-Nov-20 12:36pm

I obviously can't

Dave Kreskowiak 25-Nov-20 13:35pm

Use the debugger and step through the code line by line to watch it execute. It will teach you a lot about what your code is doing.

The debugger is there to debug YOU, not the code. It's there to change your understanding of what the code is doing.

Richard MacCutchan 25-Nov-20 13:51pm

You need to change the value inside the loop by comparing the entered password with whatever it is supposed to be.

KarstenK · Answer 2 · 2020-11-25T07:24:00

When you would use the debugger you see with your own eyes, that your renew is NEVER updated in your while loop.

By the way: hard coded password in source code are very bad, because they are landing also in the executable and anybody a bit clever can see them with some binary file viewer. At top they are finely sorted from the linker in the resources block. :-O

Patrice T · Answer 3 · 2020-11-25T07:48:00

Quote:
Why the do..while loop in this code doesn't end

Your code do not behave the way you expect, or you don't understand why !

There is an almost universal solution: Run your code on debugger step by step, inspect variables.
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't know what your code is supposed to do, it don't find bugs, it just help you to by showing you what is going on. When the code don't do what is expected, you are close to a bug.
To see what your code is doing: Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]

Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]
Basic Debugging with Visual Studio 2010 - YouTube[^]

1.11 — Debugging your program (stepping and breakpoints) | Learn C++[^]

The debugger is here to only show you what your code is doing and your task is to compare with what it should do.

Richard Deeming · Answer 4 · 2020-11-25T23:19:00

Quote

C++

bool renew = ((userpassword != password1) || (userpassword != password2)|| (userpassword != password3));

This condition will always be true, since the three passwordN variables are different. If userpassword is equal to any one of them, it will not be equal to the others. You should be using && instead of || here.

Logical OR operator: || | Microsoft Docs[^]
Logical AND Operator: && | Microsoft Docs[^]

Also, as others have pointed out, you never update the value of the renew variable inside the loop. You initialize it once, outside of the loop, before the userpassword variable has been initialized. You need to move the test inside the loop.

Why doesn't the do.. While loop end?

4 solutions

Solution 1

Solution 2

Solution 3

Solution 4

Add your solution here

Preview 0