Graphics Console

When you write simple programs and run it, the output is shown in a text based console like Command Prompt and Terminal. The problem with these console is that, it is designed to represent text only. So, you can't draw any shapes in it. Somehow, even if you try to draw any shapes like circle using characters, it will not be accurate. So, we need a window in which we can draw any kind of shapes easily and here comes the concept of console in graphics mode.

This graphics window is basically a lot of pixels arranged in rows and columns. Pixel is nothing but the smallest point in raster image. Even your monitor and phone display is made of smallest addressable element which is known as pixel (or Picture Element). These pixels have a special property that it holds color data and when you see all these pixels together, it appears to be an image of something and that is how it works.


Creating Graphics Window

So, now we know why do we need to create graphics window (or graphics console). But now the question is How to create a graphics window? So now we will create new program in CodeBlocks in C++ language which will create a graphics window. We will use "graphics.h" library for it. To setup graphics.h in CodeBlocks, read (How to setup "graphics.h" in CodeBlocks?).

So, lets create a new C++ program which will open console in graphics mode. Open CodeBlocks, Create a new project and write the following code.


#include <graphics.h>

int main()

{

    int gd=DETECT, gm;

    initgraph(&gd, &gm, (char*)"C:\\TC\\BGI") ;

    getch();

    closegraph();

    return 0;

}

 

Code Explanation

    As we are using "graphics.h", So in the first line I have included graphics.h header file. Thereafter, in the main function, you can see I have declared two integer variables gd and gm. The variable gd will store the value of graphics driver. You can notice that I have initialized it with DETECT so that, at the time of creating a graphics window, the appropriate  value of graphics driver will be automatically detected and assigned to variable gd. The second variable gm will hold the value of graphics mode.

    In the next line, I have called initgraph function which is used to create graphics window. It takes three integer arguments. The first one is initeger pointer to the variable which will hold the value of graphics driver. So, I have passed address of variable gd. Second one is integer pointer to the variable which will hold the value of graphics mode and therefore I have passed address of variable gm. The third argument is the path to the driver. You can notice, I have passed "C:\\TC\\BGI" in it.

NOTE: (i) In C++, anything that you write in double quotes "" is treated as string constant by modern compilers and initgraph function require char* in its third argument. Due to this type mismatch, we will get a warning which says "deprecated conversion from string constant to char*" and to solve it in the above program, (char*) is written to explicitly convert the path from string constant to char*.

(ii) The path provided is used in Turbo C++ IDE and it can be different in your case depending upon how Turbo C++ is installed in your computer and in CodeBlocks, it is not mandatory to write the whole path. If you pass an empty string, even then your program will work.

    In the next line, I have called the getch function to hold the output on the screen until you press any key from your keyboard. Thereafter, I have called closegraph function which is used to close the graphics window.

    Finally, as the main function return an integer, so I have written return 0 which means the program has been executed successfully.

    One more thing you can notice in the program that I have used getch function which is declared in conio.h header file but I have not included conio.h in the program. Actually conio.h is not a standard header file and therefore modern compilers (like MinGW) don't have it. But the graphics library that we are using is upgraded version specially designed for these modern compilers and it also contains some useful functions which belongs to non-standard header files but you need them when using graphics.h and getch is one of those function declared in graphics.h.

Now build and run the program. You can use F9 key also.


Output

So, in the above output, you can see a graphics window is created. The top-left corner is the origin i.e. here, the value of x and y coordinates is zero. The value of x increases as you go from left to right and the value of y increases from top to bottom of this window. In other words, you can say it is a two dimensional coordinate system with y-axis inverted and the origin at top-left corner of this window.


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