What is AGI?

AGI stands for Adventure Game Interpreter. It is basically a specially designed computer program that can "interpret" a set of resources in order to make a fully graphic, interactive game. It was developed in the early-mid eighties by a computer game company then called Sierra On-Line. They used this interpreter with the games which they developed from 1984 to 1989.

The games made with AGI are quite blockly at a resolution of only 200x160, and only have 16 colors (but believe me, that was quite remarkable for the time, as most games only 4 colors).  I will tell you however, that looking at them with their blockly graphics does not make me think that they are awful graphics, rather they bring back a great feeling of nostalgia.  I imagine many feel this way. Sierra boasted that the AGI games were the first to contain 3-D graphics, which isn't true in the sense that more recent games are 3-D, but they did nearly simulate it. Characters could walk behind, and in front of objects, as well as other characters. There definitely existed a sense of not just moving right, left, up and down, but also toward the player and away from them.  These graphics really allow those who made them to stretch their minds with creativity.

One of the truly great aspects of these games was the parser interface. All commands how to be typed, as the mouse was not a readily available accessary at the time.  In many ways this allowed the player a much greater freedom than the point and click games of today.  It challenged their mind and their typing skills, especially when the player had to type "pound stake into dracula" before Dracula woke up!

The first game they made was called King's Quest. King's Quest was perhaps the most innovative and technologically advanced game ever to hit the market. (In many respects, it is still quite remarkable).  It has since gone down in computer-gaming history as one of the biggest and best games of all time. A sequel soon followed, and then another.  During AGI's big years, Sierra developed over thirteen games using AGI. These games are:

King's Quest - 1984 (Later retitled King's Quest 1: Quest for the Crown)
King's Quest II - Romancing the Throne - 1985
The Black Cauldron - 1986
King's Quest III - To Heir is Human - 1986
Space Quest I - The Sarien Encounter - 1986
Space Quest II - Vohaul's Revenge - 1987
Mixed-Up Mother Goose - 1987
Police Quest I - In Pursuit of the Death Angel - 1988
Leisure Suit Larry in the Land of the Lounge Lizards - 1988
King's Quest IV - 1988
Manhunter New York - 1988
Goldrush - 1989
Manhunter 2: San Francisco - 1989

There are several others such as Donald Duck's Playground and a few other Disney related games (Winnie the Pooh and a Mickey Mouse one). These Disney titles are difficult if not impossible to find now, but I know they existed at one time because I used to own them.

In 1988, Sierra created SCI, the Sierra Creative Interpreter, which they slowly converted to over a two year period. By the beginning of 1990, it had completely taken over. King's Quest IV was made using both AGI and SCI.

The interpreter itself is an executable file, with several drivers, which "interprets" the material or the resource files which the programmer gives to it. These following files are included as the "interpreter":

AGI - this file is the interpreter itself
Sierra.com - (sometimes instead of "sierra" is the game's name) this file loads the interpreter
Agidata.ovl - a driver for the interpreter
Cga_graf.ovl - a driver for CGA graphics
Ega_graf.ovl - a driver for EGA graphics
Hgc_font - a driver
Hgc_graf.ovl - a driver
Hgc_objs.ovl - a driver
Ibm_objs.ovl - a driver
Jr_graf.ovl - a driver

Of course, these files simply make up the interpreter, and the interpreter alone is not a game. What makes up the game is the material which AGI interprets, typically called the "resource" files.  These files include:

Picdir - this file contains the pictures (the backrounds) the game uses.
Viewdir - this file contains the views (or the animated graphics) the game uses.
Snddir - this file contains the sounds and music the game uses.
Logidr - this file contains the logic files which actually contains the actual programming.
Object - this is a list of all the objects (inventory items) the player can get
Words.tok - this file lists all words and synonyms the game will understand
Vol.0 - this file actually holds all of the data for the game

After Sierra already invented the interpreter, when they wanted to make a new game, they only had to produce the seven previous resource files in order to do so. This made making a game so much quicker and simpler since it didn't have to be programmed from scratch.

In the 1990's, years after Sierra had completely abandoned using AGI, several people from across the world got together in order to decipher AGI and how it worked. By 1997, they had fully figured out what each of the previous files in an AGI game did. It didn't take long before they began to develop tools themselves  in order to not only alter these files, but create them. Several different utilities were made to do so, but they were often complicated and crude. In early 1998, AGI Studio was released. This program put together many of the previous utilities into one convenient application.  This program allowed full editing of all the game files (the latter seven) except Snddir and Picdir. Another program, PicEdit, was released earlier which allowed editing of Picture files which could be used in the Picdir file. As of this writing, there still exists no good editor for Sounds (which go into the Snddir file).  However, sound files can be created in other ways, and thus there is enough for fans of Sierra and AGI everywhere to make games of their own.

So, the legacy of AGI continues on, well beyond what Sierra ever could imagine...