Confused: What is wrong with void??

Machewy · 04-12-2003, 08:05 PM

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';

}

Is it okay to do what I just did?

The Dog · 04-12-2003, 08:10 PM

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)

XSquared · 04-12-2003, 08:27 PM

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.

CheesyMoo · 04-12-2003, 08:41 PM

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

Look at this:

Code:

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.

XSquared · 04-12-2003, 08:44 PM

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.

alpha · 04-12-2003, 08:46 PM

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

biosninja · 04-14-2003, 11:39 AM

Maybe you could ask Prelude?

DirX · 04-14-2003, 09:06 PM

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

.

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.

Xei · 04-14-2003, 10:32 PM

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

DirX · 04-14-2003, 10:45 PM

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.

XSquared · 04-14-2003, 10:47 PM

>>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.

DirX · 04-14-2003, 10:50 PM

.... 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....

XSquared · 04-14-2003, 10:59 PM

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

Xei · 04-14-2003, 11:31 PM

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!

HybridM · 04-15-2003, 04:13 AM

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.

04-12-2003, 08:05 PM	#1
Machewy Registered User Join Date: Apr 2003 Posts: 42	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'; } Is it okay to do what I just did? __________________ "All things come to an end"
Machewy is offline

04-12-2003, 08:10 PM	#2
The Dog Registered User Join Date: May 2002 Location: Cape Town Posts: 777	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)
The Dog is offline

04-12-2003, 08:27 PM	#3
XSquared C++ Developer Join Date: Jun 2002 Location: UWaterloo Posts: 2,718	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. __________________ Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie
XSquared is offline

04-12-2003, 08:41 PM	#4
CheesyMoo The Pantless Man Join Date: Jan 2003 Posts: 262	So does Bjourne mean that you don't have to return a number after main()? Look at this: Code: 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. __________________ If you ever need a hug, just ask.
CheesyMoo is offline

04-12-2003, 08:44 PM	#5
XSquared C++ Developer Join Date: Jun 2002 Location: UWaterloo Posts: 2,718	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. __________________ Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie
XSquared is offline

04-12-2003, 08:46 PM	#6
alpha Registered User Join Date: Nov 2002 Posts: 1,109	it's also good practice to type return 0; at the end of main.
alpha is offline

04-14-2003, 11:39 AM	#7
biosninja Bios Raider Join Date: Jul 2002 Location: South Africa Posts: 765	Maybe you could ask Prelude? __________________ The knack of flying is learning to throw yourself at the ground and miss.
biosninja is offline

04-14-2003, 09:06 PM	#8
DirX Registered User Join Date: Aug 2002 Posts: 87	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 . 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.
DirX is offline

04-14-2003, 10:32 PM	#9
Xei Registered User Join Date: May 2002 Posts: 719	I use void main() to test things in the console. Not for anything else. __________________ "What are you after - the vague post of the week award?" - Salem IPv6 Ready. Travel the world, meet interesting people...kill them. Trying to fix or change something, only guaruntees and perpetuates its existence. I don't know about angels, but it is fear that gives men wings. The problem with wanting something is the fear of losing it, or never having it. The thought makes you weak. E-Mail Xei
Xei is offline

04-14-2003, 10:45 PM	#10
DirX Registered User Join Date: Aug 2002 Posts: 87	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.
DirX is offline

04-14-2003, 10:47 PM	#11
XSquared C++ Developer Join Date: Jun 2002 Location: UWaterloo Posts: 2,718	>>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. __________________ Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie
XSquared is offline

04-14-2003, 10:50 PM	#12
DirX Registered User Join Date: Aug 2002 Posts: 87	.... 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....
DirX is offline

04-14-2003, 10:59 PM	#13
XSquared C++ Developer Join Date: Jun 2002 Location: UWaterloo Posts: 2,718	Actually, in 4 months of running XP Pro, I've gotten more BSODs than in 2 years of 98SE. :P __________________ Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie
XSquared is offline

04-14-2003, 11:31 PM	#14
Xei Registered User Join Date: May 2002 Posts: 719	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! __________________ "What are you after - the vague post of the week award?" - Salem IPv6 Ready. Travel the world, meet interesting people...kill them. Trying to fix or change something, only guaruntees and perpetuates its existence. I don't know about angels, but it is fear that gives men wings. The problem with wanting something is the fear of losing it, or never having it. The thought makes you weak. E-Mail Xei
Xei is offline

04-15-2003, 04:13 AM	#15
HybridM Grammar Police Join Date: Jan 2003 Posts: 355	BSODs 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. Last edited by HybridM; 04-15-2003 at 04:16 AM.
HybridM is offline

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Inserting a swf file in a windows application	face_master	Windows Programming	12	05-03-2009 11:29 AM
My Rpg system(Text)	kevinawad	C++ Programming	56	06-25-2008 07:04 PM
i cannot see the mouse arrow	peachchentao	C Programming	6	12-10-2006 04:14 AM
need help with handelling multiple source files	DarkMortar	C++ Programming	38	05-26-2006 10:46 PM
oh me oh my hash maps up the wazoo	DarkDays	C++ Programming	5	11-30-2001 12:54 PM

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode