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In case you don't know allegro is an open source game programming library developed by shawn hargraves. Allegro is probably one of the most well known game libraries and also one of the oldest.

Allegro was first developed with the intention of providing easy access to mode13 in msdos using the djgpp compiler. Because of its opensource nature other people began submitting their own bits of code into allegro helping it to grow into a fully featured game development library with support for many resolutions and drawing functions. The most recent release (V4.0) has added a huge amount of support for platforms (All Windows platforms were gaming is popular, Linux, FreeBSD, QNX, BeOS, Mac) and compilers (just about any compiler that can run ANSII C++ including Microsoft Visual C++, Mingw, Dev++, DJGPP, cygwin, GCC).

Features

With the advent of V4.0 allegro has become fairly complete with many features including,

Easy structure - Pretty much everything on screen is a bitmap including all images, primitives and the screen itself. This makes manipulating objects on the screen easy. a bitmap in allegro is similar to a surface in SDL.

Image file loading - Allegro can by default load a few popular image file formats such as BMP files and can be made to load more formats if addons are installed.

Sound file loading - Allegro can by default load a few popular file formats such as WAV files and can be made to load more formats if addons are installed.

2D screen drawing - Allegros allows the drawing of previously loaded files or 2D primitives such as rectangles and circles.

3D screen drawing - The inbuilt 3D functions are not as complete as those found in other library's but allegro supports opengl (the standard in 3D programming) as an addon library.

Ease of use

One of the primary aims of allegro is to be easy to use for the beginner. This is the area that allegro scores most highly in. It is very easy for an almost complete beginner to at least start creating the game because almost all of the hardware specific details are hidden from them and it is left up to the developer to design the game. All that is required to make it run on any platform is adding allegro_init() before any other allegro functions and END_OF_MAIN right underneath the main statement and allegro will figure out what needs to be done.

The allegro functions are fairly simple, flexible and will not take much time to learn for most people. The official documentation on the other hand is not the best for complete beginners since it is mostly a technical view of the library functions and not tutorials for getting started as in other library's such as clanlib. Although there are a few unofficial sites that offer to teach the basics of allegro. Go to the bottom of this page to see them.

The best of these unofficial sites has to be allegro.cc. As well as allegro files and links to other allegro websites it acts as a showcase for games from allegro developers. Hundreds of allegro based games can be downloaded from action to strategy. The forums are another area of the site that work very well, almost all questions are answered.

I do think that there should be a few more high level functions to help simplify game development. I understand that allegro is a low level game library but since this is clearly aimed at the beginner, why not for example, have inbuilt functions for tile maps? Most games created with allegro use tile maps in one way or another so introducing a standard wrapper to create tile maps makes sense.

Here's some example code that draws an image on screen,

#include <allegro.h>

int main()
{

// This is the bitmap that stores the image
BITMAP *the_image;

// The initialization code needed to make allegro work
allegro_init();

// Self explanatory
install_keyboard();

// Full screen mode with a resolution of 800 by 600
set_gfx_mode(GFX_AUTODETECT_FULLSCREEN , 800, 600, 0, 0);

// read in the bitmap file
the_image = load_bitmap("test.bmp", NULL);

// blit the image onto the screens center
blit(the_image, screen, 0, 0, (SCREEN_W-the_image->w)/2, (SCREEN_H-the_image->h)/2, the_image->w, the_image->h);

// destroy the bitmap
destroy_bitmap(the_image);

// Waits for user input
readkey();

}

// Some Allegro magic to deal with WinMain().
END_OF_MAIN();

And so

Even though it has a few (small) problems its advantages still make it one of the best 2D game library available today. It is more then capable of creating good games, for examples just take a look at allegro.cc. Looking at the design documents for allegro V5.0 it seems like allegro is going to keep improving in both platform support and performance.

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Links

Allegro.cc - the allegro "Game Developing Community Network".

AGDN - "Allegro Game Development Network".

LoomSoft - Has an "Allegro Newbie Tutorial".