System cls c что это

System cls c что это

It is one of the basic need a program may required i.e clear the console during execution time.

Need of a clear console screen :

A console screen must be cleared once its stated objectives have been completed. A user also needs a clear screen for new data. Like any other language, C offers a variety of ways to clear the console screen.

The clear screen method or function not only depends on types of operating systems but also compilers, which include modern as well as older compilers

There is function named clrscr() which is included in conio.h and is a nonstandard function and is present in conio.h header file which is mostly used by MS-DOS compilers like Turbo C. It is not part of the C standard library or ISO C, nor is it defined by POSIX.
So what should we use there?
There are two more ways to clear console:

1. By Using system(“clear”)
2. By using a regex “\e[1;1H\e[2J”
3. by using clrscr() function
4. System(“cls”)

The following are some of the factors that influence a console’s clear screen:

1. Type of operating system.
2. User compiler new or old.
3. Need of the user.

Prerequisites :

1. Some clear screen methods are platform specific. They won’t run on other systems or compilers.
2. If you are using a visual studio then prefer the system.(“cls”)

clrscr()

clrscr() is an abbreviation of the clear screen. It aims to clear the console screen. clrscr() is a library function located in the console input output header file <conio.h>. The previous screen on the console is cleared whenever the clrscr () is invoked in a program. To call the clrscr() function, it must define inside any function or the main function.

Properties :

1. Window Specific
2. Supported by older compiler
3. Doesn’t allocate extra resource.

Syntax

Parameter:

Return :

Example :

let’s take an example that will display the addition of two numbers using clrscr().

System cls c что это

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Clearing the Screen, Flush, and Pause

When the screen is cleared in Visual C++, the cursor is moved to the upper left corner of the screen. To clear the screen in Visual C++, utilize the code: system("CLS");
The standard library header file <stdlib.h> is needed.

Note: If you wish to clear the screen after a cout statement, you will need to "flush" the iostream.

You will discover that it will be necessary on occasions to "clear the output stream". All information going "out" to the screen goes through the output stream. (Thus the header named <iostream.h> — input/output stream.)

To force the information to go to the screen immediately (and not wait for more information to enter the stream before outputting to the screen), we will be using flush.

The correct syntax will be:

cout << "Flushing the output stream." << flush;

Note: This command will "pause" the screen and display the message "Press any key to continue . . . " as it waits for a keystroke. If you wish to pause the screen after a cout statement, you will need to "flush" the iostream. (Requires header file <stdlib.h> )

#include <iostream.h>
#include <stdlib.h>

Let’s see what the output from this program will look like. The screen display is shown in the table below. The cells of the table are used to represent the coordinates of the screen.
Refer to your grid sheet.

Of course, there are more than 19 columns across your screen (there are 80). Notice the following things:

std::system

Calls the host environment’s command processor (e.g. /bin/sh , cmd.exe , command.com ) with the parameter command . Returns an implementation-defined value (usually the value that the invoked program returns).

If command is a null pointer, checks if the host environment has a command processor and returns a nonzero value if and only if the command processor exists.

Parameters

Return value

Implementation-defined value. If command is a null pointer, returns a nonzero value if and only if the command processor exists.

Notes

On POSIX systems, the return value can be decomposed using WEXITSTATUS and WSTOPSIG.

The related POSIX function popen makes the output generated by command available to the caller.

An explicit flush of std::cout is also necessary before a call to std::system , if the spawned process performs any screen I/O.

Какие команды можно передавать в system(" ")

Мне известно пару команд: system("cls") , system("pause") , например. Напишите, пожалуйста, какие еще команды можно использовать в system(" ") и что они выполняют.

в функцию system можно передавать любые команды, которые могут быть выполнены в командном процессоре или терминале операционной системы

следует знать, что вызов этой функции ресурсоемок, а также использование этой функции делает программы не переносимой между различными системами, так как различные ОС имеют разные команды

для просмотра самых популярных команд windows можно ввести команду help в терминале, или вызвать функцию system с командой help в с++ программе на windows, все команды можно просмотреть в онлайн документации