зачем нужна system("pause >nul");

#include <iostream>
 
using namespace std;
 
static char game_arr[10] = "123456789";
bool player = 1;
 
void first_win() 
{
    cout << "ïåðâûé èãðîê(X) ïîáåäèë!";
    system("pause >nul");
    exit(0);
}
 
void second_win() 
{
    cout << "âòîðîé èãðîê(O) ïîáåäèë!";
    system("pause >nul");
    exit(0);
}
 
void test_win()
{
    for (int i = 0; i < 3; ++i)
        if (game_arr[i] == 'X' && game_arr[i + 3] == 'X' && game_arr[i + 6] == 'X') first_win();
    for (int i = 0; i < 9; i += 3)
        if (game_arr[i] == 'X' && game_arr[i + 1] == 'X' && game_arr[i + 2] == 'X') first_win();
    for (int i = 0; i < 3; ++i)
        if (game_arr[i] == 'O' && game_arr[i + 3] == 'O' && game_arr[i + 6] == 'O') second_win();
    for (int i = 0; i < 9; i += 3)
        if (game_arr[i] == 'O' && game_arr[i + 1] == 'O' && game_arr[i + 2] == 'O') second_win();
    if (game_arr[0] == 'X' && game_arr[4] == 'X' && game_arr[8] == 'X')  first_win();
    if (game_arr[0] == 'O' && game_arr[4] == 'O' && game_arr[8] == 'O')  second_win();
    if (game_arr[2] == 'X' && game_arr[4] == 'X' && game_arr[6] == 'X')  first_win();
    if (game_arr[2] == 'O' && game_arr[4] == 'O' && game_arr[6] == 'O')  second_win();
}
 
void write(char arr[])
{
    for (int i = 0; i < 9;i += 3) 
    {
        cout << arr[i] << arr[i+1] << arr[i+2] << endl;
    }
}
 
void step()
{
    int newstep;
    if (player) 
    {
        cout << "ïåðâûé èãðîê(X) õîäèò: ";
        cin >> newstep;
        if (game_arr[newstep - 1] != 'X' && game_arr[newstep - 1] != 'O') {
            game_arr[newstep - 1] = 'X';
            player = !player;
        }else {
            cout << "äóäà óæå õîäèëè!";
            system("pause >nul");
        }
    }
    else
    {
        cout << "âòîðîé èãðîê(O) õîäèò: ";
        cin >> newstep;
        if (game_arr[newstep - 1] != 'X' && game_arr[newstep - 1] != 'O') {
            game_arr[newstep - 1] = 'O';
            player = !player;
        }else{
            cout << "äóäà óæå õîäèëè!";
            system("pause >nul");
        }
    }
}
 
void loop() 
{
    while (true) 
    {
        write(game_arr);
        test_win();
        step();
        system("cls");
    }
}
 
void main()
{
    system("title êðåñòèêè íîëèêè");
    system("chcp 1251 >nul");
    loop();
}