Really new to programming

[MuggerHugger]

Hi, everyone. I am very new to the whole programming thing so if my questions seem pretty stupid I apologize. I was curious about something. I am trying to improve my data validation techniques and I wanted to know if there was a way to stop my computer from going nuts if a user enters an incorrect data type into a variable.


I have this very small program that asks the user to enter the number of cookies they have eaten and it will tell them the amount of calories they consume. This is what I have so far:

#include <iostream>
using namespace std;


int main ()
{

    int amount;
    int perCookie = 30;
    int total;
    
    cout<<"              Calorie Counter\n\n";
    cout<<"Please enter the amount of cookies you consumed:"; //prompt the user for cookies consumed
    cin>>amount; //accept user data
    while( amount > 40 || amount < 1) //validate user input
    {
        cout<<"That is an invalid response\n";
        cout<<"Please enter an amount less than 40 or greater than 0\n\n";
        cout<<"Please enter the amount of cookies you consumed:";
        cin>>amount;
    }
    total = perCookie * amount; //calculate the total
    cout<<"Amount of calories your consumed: " << total <<"\n\n\n\n";
    




system("PAUSE");
return 0;
}

I have it so that they have to enter a number greater than 0 but less than 40 because there is only 40 cookies in the bag. I was curious what would happen if I entered A into the amount variable and when I put it in the program crashed.

How would I prevent that from happening? I would like to prompt them to enter a number not a letter but I don't know what way I would go about validating that.

[Thu]

while(cin>>amount)
{
    // Anything you love to do
    
    // Insert your break here
    if(>40 OR <1)
       break;
}

This offers better coding style, performance-wise

[laserlight]

I have it so that they have to enter a number greater than 0 but less than 40 because there is only 40 cookies in the bag. I was curious what would happen if I entered A into the amount variable and when I put it in the program crashed.

How would I prevent that from happening? I would like to prompt them to enter a number not a letter but I don't know what way I would go about validating that.

In addition to checking for valid values, check if the read succeeded and clear the error flags, e.g.,

cin>>amount; //accept user data
while(cin.fail() || amount > 40 || amount < 1) //validate user input
{
    cout<<"That is an invalid response\n";
    cout<<"Please enter an amount less than 40 or greater than 0\n\n";
    cout<<"Please enter the amount of cookies you consumed:";

    cin.clear(); // Clear the error flags.
    // Ignore what was left on the buffer in preparation for new input.
    cin.ignore(numeric_limits<streamsize>::max(), '\n');
    cin>>amount;
}

You should #include <limits> for std::numeric_limits and #include <ios> for std::streamsize.

[MuggerHugger]

Ok, thanks a lot.

[TheCPUWizard]

Ok, thanks a lot.

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