Why does it do this?!?

This is a discussion on Why does it do this?!? within the C++ Programming forums, part of the General Programming Boards category; Hello folks, I am a newbie to programming. I will be using C++ over the summer for an independent study ...

  1. #1
    Registered User
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    May 2005
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    2

    Why does it do this?!?

    Hello folks, I am a newbie to programming. I will be using C++ over the summer for an independent study course in Computational Physics, so I HAVE to get good at this within the next month. I have been practicing a lot, but I still know little about it, only what I have learned from this website and some terrible books I own.

    Anyway, just practicing today, I rewrote a program (which I based off of another simpler one I found in a book). Here it is:

    Code:
    #include <iostream>
    
    using namespace std;
    
    int main()
    {
        int num1, num2, total;
        cout << "Enter a positive whole number that is less than or equal to 10: ";
        cin >> num1;
        if ( num1 > 10 )
        { cout<<"This number is NOT less than or equal to 10\n";
        cout << "Please enter a positive whole number that is less than or equal to 10: ";
        cin >> num1;
    }
        if ( num1 < 0 ) 
        { cout<<"This is NOT a positive number\n";
        cout << "Please enter a positive whole number that is less than or equal to 10: ";
        cin >> num1;
    }
        cout << "Now enter another number: ";
        cin >> num2;
        cin.get();
        total = num1 + num2;
        cout << "Your numbers total\n" << total << endl;
        cin.get();
        return 0;
    }
    The program works just fine if I type in 4 and 6, but here is the problem. I want someone to enter a number that is less than or equal to 10, so if I enter 11, the program returns the message "This number is NOT less than or equal to 10. Please enter a positive whole number that is less than or equal to 10". This works fine, except that if I enter 11 once again, it just goes on to the next question in the program. So it will not accept a number > 10 the first time, but it will if you enter it a second time. This also happens if you enter a negative number after it has already prompted you to enter a positive number. Why is this?!? Thanks a lot for your time!!!


    säki

  2. #2
    Slave MadCow257's Avatar
    Join Date
    Jan 2005
    Posts
    735
    The problem is that that second time around, you've passed the num1 > 10 part and it checks if num1 < 0. This is true, so it accepts it and moves on to adding.

    Here's a solution...
    Code:
    #include <iostream>
    
    using namespace std;
    
    int main()
    {
        int num1, num2, total;
        cout << "Enter a positive whole number that is less than or equal to 10: ";
        cin >> num1;
        while (num1 > 10 || num1 < 0)
    	{
    		if (num1 > 10)
    			cout<<"This number is NOT less than or equal to 10\n";
    		else
    			cout<<"This is NOT a positive number\n";
    		cout << "Please enter a positive whole number that is less than or equal to 10: ";
    		cin >> num1;
    	}
        cout << "Now enter another number: ";
        cin >> num2;
        cin.get();
        total = num1 + num2;
        cout << "Your numbers total\n" << total << endl;
        cin.get();
        return 0;
    }

  3. #3
    Registered User
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    May 2005
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    2
    Excellent!!! Thank you very much!!!

    säki

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