Thread: Noobie question

The code is below and from this sites tutorials. It is a multiplication program. But it has bugs, if I type a letter it will crash or make some error, likewise if I type a large number it will have problems. Isn't there someway to get it to output an error message and ask me to try again?

#include <iostream.h>



int mult(int x, int y);



int main()

{

int x, y;

cout<<"Please input two numbers to be multiplied: ";

cin>>x>>y;

cout<<"The product of your two numbers is "<<mult(x, y);

return 0;

}

int mult(int x, int y)

{

return x*y;

}

An int cannot hold a char value such as a letter, and ints can only hold so much data before overflow errors occur. You can prevent it by making sure the input is less than or equal to MAX_INT in values.h or something

I have no problems with your code, try this:

Code:

#include <iostream>
#include <conio.h>

using namespace std;

int mult(int x, int y);

int main()
{
	int x, y;

	cout<<"Please input two numbers to be multiplied: ";

	cin>>x>>y;

	cout<<"The product of your two numbers is "<<mult(x, y);

	getch();
	return 0;
}

int mult(int x, int y)
{
	return x*y;
}

PS: Use code /code tags between []

whatever the reply was made very little no sense I AM A NOOB I understand that an integer isnt a character-however instead of this program saying

An integer is not a character! Please try again!

it will crash

I have no idea what a MAX_INT is or what a values.h is

all i wanna do is have it say

if input != number
then
try again

if input > toobig
then
i donno do something besides crash

as for the second example I cant compile it the compiler says that a namespace name is expected i am getting lots of errors like that from other peoples tutorials for instance in the book i have it talks about using
#include "string6.h" which it never says what that is and it never says what to do if my compiler says that it doesnt know what that is

and what does PS: Use code /code tags between [] mean? i have not a clue

code tag info here:

http://www.cprogramming.com/cboard/s...threadid=13473

use them.

here is a simpler program with the same problem - inputting a letter or large number causes it to crash or have some outrageous error

also the name unregistered seems to be registered which presents a problem for noobies

Code:

#include <iostream.h>

int main()

{
  int i;

  char thisisanumber[256];

  cout<<"Please enter a number:";

  cin>>thisisanumber;

  cout << "You entered: ";

  i = 0;

  while (thisisanumber[i] >= '0' && thisisanumber[i] <= '9')
  {
    cout << thisisanumber[i];
	i++;
  }

  cout << endl;

  return 0;

}

U can't enter a char, if u have declerated an int!!!!

Thats just it! I CAN enter a char, if u run these programs and type a letter instead of a number, it will try to use the letter when it should say, "I didnt ask for a letter, I asked for a number! Please try again!"

Well, you're right, Noobie, real world programs need to be bullet-proof (or user-proof"). These types of protections are often left out of example programs because it complicates them, making it harder to see the point of the example. C++ provides "exception handling" when you want to get fancy. Most of my programs have a default value/choice, which is used it the user just presses ENTER, or enters something invalid.

well i guess i want an example of a real-world program that does what these programs do.

I think I partially solved it-the below code has the user choose between 1 and 2-with a different choice resulting in a re-request for choices-however, the above question about large numbers still remains unanswered

Code:

#include <iostream.h>			

int main()
{

  int choice;
  int room;

  while(x==0)	

 {

    cout<<"Please choose a room (1 or 2): ";	

    cin>>choice;	  

if(choice==1)
x=x++
else if(choice==2)
x=x++
else
x=x        		
  } 				

  if(choice==1)				

  {

  		room=1;
     cout<<"You enter a room\n";    

  }

  else if(choice==2)		

  {
  		room=2;

     cout<<"You are in room 2\n";		

  }

  else

  {

    cout<<"You should not see this.\n";

  }

  if (room==1)
  {
  cout<<"Yep";
  }
  else if (room==2)
  {
  cout<<"Nope";
  }
  else
  {
  cout <<"I need to know how to ask them to plz enter a proper room choice, but how to do that? i don't know.";
  }
  return 0;

}

However, the program crashes if a letter is entered....How can I prevent that?

Originally posted by Noobie
However, the program crashes

Define crash, does it just quits? does crash windows? what?

You must return a value from main, in this case an int

Code:

 int main()
{
return 0;
}