Allegro is a game programming library for C/C++ developers distributed freely, supporting the following platforms: Unix (Linux, FreeBSD, etc.), Windows, MacOS X and Haiku/BeOS. Older versions also support DOS and QNX. It provides many functions for graphics, sounds, player input (keyboard, mouse and joystick) and timers. It also provides fixed and floating point mathematical functions, 3d functions, file management functions, compressed datafile and a GUI.

Allegro is a portable library mainly aimed at video game and multimedia programming, originally started by Shawn Hargreaves for the DJGPP compiler in a mixture of C and assembler.

According to the Oxford Companion to Music, Allegro is the Italian for «quick, lively, bright». It is also a recursive acronym which stands for «Allegro Low LEvel Game ROutines».

Cross-platform support

* Unix (Linux, FreeBSD, Irix, Solaris, Darwin)
* Windows (MSVC, MinGW, Cygwin)
* MacOS X
* Haiku/BeOS

The older 4.2 branch also supports:

* Windows (Borland)
* QNX
* DOS (DJGPP, Watcom)

Graphic functions

* Vector drawing:
o pixels, lines, rectangles, circles, ellipses, arcs, Bezier splines
o shape fill, with or without pattern
o polygons: flat, Gouraud, textured (3D) and translucent
* Sprites:
o masked, compressed and compiled sprites
o blitting, rotation, stretching, reduction, alpha blending, Gouraud shading
o native support for BMP, LBM, PCX and TGA files (others supported with library extensions)
* Color palettes:
o color palette manipulation (reading, writing, conversion)
o conversion of color formats RGB <-> HSV
* Text:
o support for different encodings and conversion, default is UTF-8
o bitmap fonts (masking, colouring, alignment)
* Misc:
o draw directly on the screen or on any-size memory bitmaps
o hardware scrolling and triple buffering (where available), mode-X split screen
o animation functions for FLI/FLC format

Graphic drivers

* Unix:
o X Window, DGA, fbcon
o SVGAlib
* Windows:
o DirectX (windowed or full-screen)
o GDI
* MacOS X:
o Quartz (windowed or full-screen)
* Haiku/BeOS:
o BWindowScreen
o BDirectWindow
* OpenGL:
o The AllegroGL addon allows to use OpenGL graphics with Allegro.

The older 4.2 branch also supports:

* Unix:
o VBE/AF
o mode-X
o VGA
* DOS:
o VGA 13h mode
o mode-X (23 VGA resolution plus unchained 640x400 extended mode)
o SVGA modes in 8, 15, 16, 24 and 32 bits per pixel
o linear VBE 2.0 framebuffer access
o hardware acceleration through VBE/AF API if supported
o additional graphic drivers through FreeBE/AF project

Sound functions

* Midi:
o native MIDI music format support (with 64 simultaneous effects)
o dynamic control/response to music note on, note off, main volume, pan, pitch bend, and program change
o uses General MIDI patches
o you can read in wavetable patches for MIDI files (SF2 and GUS patches)
* Wave:
o native support of WAV and VOC file formats (playing looped forward, backwards or bidirectional)
o streaming audio
o modify volume, pan, pitch, etc during play

Sound drivers

* Unix:
o OSS
o ALSA
o JACK
o SGI AL
* Windows:
o DirectSound
o WaveOut
o MIDI system drivers
* MacOS X:
o Core Audio
o Sound Manager
o Core Audio MIDI
o QuickTime MIDI

The older 4.2 branch also supports:

* Unix:
o ESD
o aRts
* DOS:
o Adlib, SB, SB Pro, SB16, AWE32
o MPU-401