Chapter 1

1. Basics

1.1 Using RHIDE to write our first C++ program

First, you should create a new directory for this tutorial. When you have done so, start RHIDE from within it. The RHIDE startup screen should appear if it was installed properly.

At the top, there are some menus. We want to create a new project for our game. Hit Alt-P to open the Project menu. Choose "Open project". Give your new project a name, e.g. tutorial. Set up your environment according to your preferences in the Options menu (Alt-O), if you wish (e.g. I prefer 80x50 screen mode). Be sure to check -Wall in the Warnings box in the Compilers menu, as this will enable many helpful warnings. Beginners and experts alike will benefit from having the compiler spot a lot of potential bugs this way.

It is now time to write your first C++ program to check that the compiler actually works. In the Project menu, select Add item. In the dialog box that pops up, type tut1.cc and hit Enter. The name will appear in the Project Window at the bottom of the screen. Hit Esc to return. Then hit Enter again to select this project entry. Since the file does already not exist, an empty window should now pop up. In it, type:

#include <iostream.h>

int main()
{
 cout << "Hello world." << endl;
 return 0;
}

This is the classical first C++ program, it does not do anything particularly useful, but we want to make sure the compiler works. Hit F9 to make it. If there are no error messages, DJGPP is properly set up. If there are problems, re-read README.1ST that accompanies the DJGPP distribution. To run our first program, hit Ctrl-F9. The screen will flash briefly while the program does its deed. If you want to see what it did, now hit Alt-F5 to view the User Screen.

The curious reader will note that the .EXE file that our exercise has produced is very large (almost 200K). This is normal and nothing to worry about, you should remember that DJGPP is a feature-rich 32-bit protected-mode compiler. The DJGPP startup and library code detects and starts up a DPMI host, enters protected mode, takes care of a lot of memory management, reads, parses, and expands command-line arguments, loads environment variables, sets up protected-mode exception handlers, and so on. Of course, all this is wasted on a program that just prints a few characters and exits. If you really are concerned about executable size, consult the DJGPP FAQ about how to reduce its size, but once we write bigger programs this overhead will soon be negligible anyway.

1.2 Introducing Allegro

I will not waste too much time introducing the theory behind C++, for this the reader may want to consult a dedicated C++ tutorial for more information, and I assume the reader to be at least vaguely familiar with C syntax. I will explain what else we need to know once we need it. And what we need to know right now, is how to start using Allegro. Most concepts concerning the use of Allegro is covered in its own examples, you may want to take a look at them also.

So, in our tut1.cc, we add some code, to make it look like this:

#include <iostream.h>
#include <allegro.h>

int main()
{
 allegro_init();
 cout << "Ready. Beep." << endl;
 return 0;
}

Since we are now using the Allegro library, the linker is going to complain if we compile this right away. In the Options menu, choose Libraries. Type alleg there and check the box beside it. Our program will now link with Allegro if Allegro was properly installed. If it doesn't, read the Allegro FAQ. If run, this program will obviously say "Ready. Beep." instead of "Hello world.", but otherwise not do very much interesting.

1.3 Using Allegro

We will now add even more code to our little introductory program, and this time use Allegro for the output.

#include <allegro.h>

int main()
{
 allegro_init();
 install_keyboard();
 set_gfx_mode(GFX_VGA,320,200,0,0);
 textout_centre(screen,font,"Ready. Beep.",160,100,255);
 readkey();
 return 0;
}

Hit Ctrl-F9 to run it. This program does not use the C++ iostream routines to output its text, so we have removed any references to it. Instead, it enters graphics mode, writes "Ready. Beep." at the center of the screen, and waits for you to press a key before it exits. For more details about the functions used here, refer to the Allegro documentation.

Exit RHIDE and proceed to the next chapter