Advertisement
Advertisement


system("pause"); - Why is it wrong?


Question

Here's a question that I don't quite understand:

The command, system("pause"); is taught to new programmers as a way to pause a program and wait for a keyboard input to continue. However, it seems to be frowned on by many veteran programmers as something that should not be done in varying degrees.

Some people say it is fine to use. Some say it is only to be used when you are locked in your room and no one is watching. Some say that they will personally come to your house and kill you if you use it.

I, myself am a new programmer with no formal programming training. I use it because I was taught to use it. What I don't understand is that if it is not something to be used, then why was I taught to use it? Or, on the flip side, is it really not that bad after all?

What are your thoughts on this subject?

2015/06/21
1
132
6/21/2015 2:17:00 AM

Accepted Answer

It's frowned upon because it's a platform-specific hack that has nothing to do with actually learning programming, but instead to get around a feature of the IDE/OS - the console window launched from Visual Studio closes when the program has finished execution, and so the new user doesn't get to see the output of his new program.

Bodging in System("pause") runs the Windows command-line "pause" program and waits for that to terminate before it continues execution of the program - the console window stays open so you can read the output.

A better idea would be to put a breakpoint at the end and debug it, but that again has problems.

2009/07/10
86
7/10/2009 4:36:56 AM

It's slow. It's platform dependent. It's insecure.

First: What it does. Calling "system" is literally like typing a command into the windows command prompt. There is a ton of setup and teardown for your application to make such a call - and the overhead is simply ridiculous.

What if a program called "pause" was placed into the user's PATH? Just calling system("pause") only guarantees that a program called "pause" is executed (hope that you don't have your executable named "pause"!)

Simply write your own "Pause()" function that uses _getch. OK, sure, _getch is platform dependent as well (note: it's defined in "conio.h") - but it's much nicer than system() if you are developing on Windows and it has the same effect (though it is your responsibility to provide the text with cout or so).

Basically: why introduce so many potential problems when you can simply add two lines of code and one include and get a much more flexible mechanism?

2009/07/10

  • slow: it has to jump through lots of unnecessary Windows code and a separate program for a simple operation
  • not portable: dependent on the pause program
  • not good style: making a System call should only be done when really necessary
  • more typing: System("pause") is longer than getchar()

a simple getchar() should do just fine.

2009/07/10

Using system("pause"); is Ungood Practice™ because

  • It's completely unnecessary.
    To keep the program's console window open at the end when you run it from Visual Studio, use Ctrl+F5 to run it without debugging, or else place a breakpoint at the last right brace } of main. So, no problem in Visual Studio. And of course no problem at all when you run it from the command line.

  • It's problematic & annoying
    when you run the program from the command line. For interactive execution you have to press a key at the end to no purpose whatsoever. And for use in automation of some task that pause is very much undesired!

  • It's not portable.
    Unix-land has no standard pause command.

The pause command is an internal cmd.exe command and can't be overridden, as is erroneously claimed in at least one other answer. I.e. it's not a security risk, and the claim that AV programs diagnose it as such is as dubious as the claim of overriding the command (after all, a C++ program invoking system is in position to do itself all that the command interpreter can do, and more). Also, while this way of pausing is extremely inefficient by the usual standards of C++ programming, that doesn't matter at all at the end of a novice's program.

So, the claims in the horde of answers before this are not correct, and the main reason you shouldn't use system("pause") or any other wait command at the end of your main, is the first point above: it's completely unnecessary, it serves absolutely no purpose, it's just very silly.


In summary, it has to pause the programs execution and make a system call and allocate unnecessary resources when you could be using something as simple as cin.get(). People use System("PAUSE") because they want the program to wait until they hit enter to they can see their output. If you want a program to wait for input, there are built in functions for that which are also cross platform and less demanding.

Further explanation in this article.

2009/07/10

You can use std::cin.get() from iostream:

#include <iostream> // std::cout, std::cin
using namespace std;

int main() {
   do {
     cout << '\n' << "Press the Enter key to continue.";
   } while (cin.get() != '\n');

   return 0;
}

Besides, system('pause') is slow, and includes a file you probably don't need: stdlib.h. It is platform-dependent, and actually calls up a 'virtual' OS.

2017/01/31

Source: https://stackoverflow.com/questions/1107705
Licensed under: CC-BY-SA with attribution
Not affiliated with: Stack Overflow
Email: [email protected]