C++第1天：在C和C++里，要尽量避免使用 system("pause")

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system("pause")

I've never understood why system("PAUSE") isso popular. Sure it will pause aprogram before it exits. This pause is very useful when yourIDE won't waitas you test a program and as soon as the program finished thewindow closes taking all your data with it.

But using system("PAUSE") islike burning your furniture for heat when you have a perfectly goodthermostat on the wall.

Many people, instructors included, for some inexplicable reasonthink that making a call to the operatingsystem and running a system command totemporarily halt a program is a good thing. Where they get thisidea is beyond me. Reasons:

• It's not portable. This works only onsystems that havethe PAUSE commandat the system level, like DOS or Windows. But notLinux and most others...

• It's a very expensive and resource heavy function call.

  It's like using a bulldozerto open your front door. It works, but the key is cleaner, easier,cheaper. What system() doesis:

   

  1. suspend your program

  2. call the operating system

  3. open an operating system shell (relaunches the O/S in asub-process)

  4. the O/S must now find the PAUSE command

  5. allocate the memory to execute the command

  6. execute the command and wait for a keystroke

  7. deallocate the memory

  8. exit the OS

  9. resume your program

  There are much cleaner ways included in the language itself thatmake all this unnessesary.

• You must include a header you probably don'tneed: stdlib.h or cstdlib

 

It's a bad habit you'll have to break eventually anyway.

Instead, use the functions that are defined natively in C/C++already. So what is it you're trying to do? Wait for a key to bepressed? Fine -- that's called input.So in C, usegetchar() instead.In C++, how about cin.get()?All you have to do is press RETURNandyour program continues.

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