Question:
I found on the Web a simple class Screen as follows:

 /*———————————————— * s c r e e n . h * * A class to manage an ANSI text screen. Allows moving to * an x, y location and clearing the screen. *  * Copyright 1996 by Interface Technologies, Inc.  * All Rights Reserved. *———————————————-  */#ifndef __SCREEN_H#define __SCREEN_H#include class Screen{public:    Screen( )    {    }    void GotoXY( int x, int y )    {        cout << "33[" << y            << ";" << x << "H";    }    void CharXY( int x, int y, char c)    {        GotoXY( x, y );        cout << c;    }    void Clear()    {        cout << "33[2J";    }};#endif

Then I wrote a little test:

#include “screen.h”void main(){     Screen s;     s.CharXY(10,40,’A’);}

It runs (on MS-DOS), but ‘A’ is displayed on the very first position of the screen.

Can you explain the implementation of GotoXY() and why the class does not work?

Answer:
As the comment in the class says, it manages ANSI screens, so it does not workon the DOS platform.

ANSI terminals understand special chars which when printed to them, cause theterminal to treat it as a command rather than print it out. This programuses these special chars to achieve the same. There is a file inDOS called ANSI.SYS that you can load from the config.sys file by sayingdevice=ansi.sys, and that makes the shell understand ANSI control chars.

Also, your argument to CharXY may need to be in range with the terminal. Remember, the first argument is the column and the second is the row.

Hope that helps.