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:

 

suspend your program

call the operating system

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

the O/S must now find the PAUSE command

allocate the memory to execute the command

execute the command and wait for a keystroke

deallocate the memory

exit the OS

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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