Confused: What is wrong with void??

Ok,

I have been confused for a while on this:

What is wrong with using void?
Why is wrong to use 'void main()'?
Is it okay to use 'void' for your functions?
For example:

PHP Code:

---

// Tempature converstions

#include <iostream.h>

void to_celsius(float f);
void to_fahrehiet(float c);

int main()
{
 char quit;
 char selection[100];
 float temp;    
 quit = '/0';
 cout<< " _________________________________________________ "<<endl;
 cout<< " Welcome to 'Calculations For Lazies' (Version 1.0) "<<endl;
 cout<< " ------------------------------------------------- "<<endl;
 cout<< " ------------------------------------------------- "<<endl;
 cout<<endl;
 cout<< " Celsius/Farhenheit converter:"<<endl;
 cout<< " ______________________________"<<endl;
 while (quit != 'q')
 {
  cout << "1- Fahrenhiet to Celsius "<<endl;
  cout << "2- Celsius to Fahrenhiet "<<endl;
  cout << "3- To quit "<<endl;
  cout << '\n';
  cout << "Please select an option number: ";
  cin >> selection;
  
  switch (selection, 100)
  {
   case 1:
    cout <<"Enter the Fahrenhiet temperature you would like to convert: ";
    cin >> temp;
    to_celsius(temp);
    break;
   case 2:
    cout <<"Enter the Celsius temperature you would like to convert: ";
    cin >> temp;
    to_fahrehiet(temp);
    break;
   case 3:
    quit = 'q';
   default:
    cout << '\n';
    cout << '\n';
    break;
  }
 }
 return 0;
}

void to_celsius(float f)
{
 float conversion;
 conversion = (f - 32)/1.8;
 cout <<f<<" Degrees Fahrenhiet = "<<conversion<<" Degrees Celsius."<<endl;
 cout << '\n';
}

void to_fahrehiet(float c)
{
 float conversion;
 conversion = c * 1.8 + 32;
 cout <<c<<" Degrees Celsius = "<<conversion<<" Degrees Fahrenhiet."<<endl;
 cout << '\n';
} 


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Is it okay to do what I just did?:confused:

It's OK for your functions, but not for main(). main() returns an int, so you have to explicitly state that it returns an int. ISO requires main() to return an int.(if i'm not mistaken)

An explanation from Bjarne Stroustrup himself. (about void main( ) )

Yes, void is okay for functions, but it is better to return an int just so you can be sure the function didn't encounter any errors.

So does Bjourne mean that you don't have to return a number after main()?

Look at this:

Code:

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In C++ main() need not contain an explicit return statement. In that case, the value returned is 0, meaning successful execution. For example:

        #include<iostream>

        int main()
        {
                std::cout << "This program returns the integer value 0\n";
        }

---

So... that goes against alot of things I've heard.

Yep. That's what he means. You don't have to write return 0 at the end of main(), although most compilers will spit out an error if you don't.

it's also good practice to type return 0; at the end of main.

Maybe you could ask Prelude?:p

Just to put it simple it is best to return an int from main to tell the Operating System wherter or not the program ended succesfully or with some kinda error:

return 0; // To OS - No Problem
return 1; // To OS - Problem

this can be useful for the OS in some ways, havent quite figured out how though :D.

In the case of user written functions it is OK to return void but it is better to return either bool or int to indicate succes or failure of the function. This is mostly to be able to do good error-checking. It is understandeble that for some functions error-checking does is hardly unlikely to occur but when consider that you must assume the user of your program is the biggest idiot on the face of this earth as well a Murphy's Law (evrything that can go wrong, will go wrong) it is best to include as much as possible error-checking.

I use void main() to test things in the console. Not for anything else.

using void main() 'should' not give any problems with current compilers. but it is not standard and is not good pratice. For small programs it should not be to terrible but once you get into big programs and it crashes for some reason (not enough memory etc) it is good to let the OS know something is wrong.

>>it is good to let the OS know something is wrong.
Of course, if you're programming for a Windows console, its usually Windows that caused the error. And besides, Windows has enough errors to deal with on its own.

.... WHy are people always so negative about Windows =] If you think about it, it is a great OS and WinXP and Win2k have minimized the amount of crashes etc greatly....

Actually, in 4 months of running XP Pro, I've gotten more BSODs than in 2 years of 98SE. :P

Wierd. Windows just handles Exceptions differently. A new practice I am learning, Structured Exception Handling, will allow me to control such crashes from my application, and hopefully recover from the error. Many of you likely already use it :) But I was very happy when I learnt about it, I still am! It's wonderful!

You'll probably find that all your blue screens are either yours, or your hardware's fault. XP is just as, if not more stable than 2k, and is CERTAINLY more stable than 9x.

The problem with void main() is that so many tuts etc. still use it! I'm still learning C++, and the first mains i encountered were all integers, so i never questioned it. In fact this site's tutorials were my first brush with c++, unfortunately that included using c-style headers for a while.

Quote:

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[/B]this can be useful for the OS in some ways, havent quite figured out how though :D.[/B]

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I believe in DOS you check the return code by using errorlevel.

XP stable? Don't count on it... your just not running the apps he is. :p

When a program runs, your operating system expects an integer value to be placed on the stack that indicates the successfulness of the program. If the operating system does not get this int on the stack, it's possible(though not likely) for it to do some flaky stuff. int main() is just good practice.

BTW, Windows XP is terrible for gaming, and one of the slowest OS's available. Wait till you see Win 2003, you're gonna hate it with a passion.

Windows XP is fine for gaming, you just need a computer that doesn't use a crank to boot up.

Good thing i wasn't planning on using 2k3, and i hope not many of you are either. It's not for desktop pcs it's for networks.

Linux is good, OS X is (supposedly) good, but windows is good too. Most people just bash windows because of the big bad brand name it carries.

I mean that if you used the same hardware configuration and connection with different OS's, XP would most likely be the slowest. I think maybe we gettin a little bit off topic...

>> using void main() 'should' not give any problems with current compilers.

>gcc 3.2 refuses ``void main''. Would you say it's not a relevant compiler, or won't soon be?

the should was placed in parenteses as that was to the best of my knowledge =] i am not saying that any compiler is better then another