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NAGI FAQ - by Nick Sonneveld

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First post, by Snover

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What is AGI?

AGI, or the Adventure Game Interpreter, was developed by Sierra Online for the development and release of their adventure games in the late 1980's. Sierra was hailed for creating "3D" games, which meant the player could move their character around the screen and behind objects. Games using the interpreter have very distinctive blocky graphics and a text parser interface where the player could type in their commands.

The AGI interpreter was the starting point for many of Sierra's classic adventure game lines:

  • Kings Quest Series
  • Leisure Suit Larry Series
  • Police Quest Series
  • Space Quest Series

What is NAGI?

NAGI (New Adventure Game Interpreter) is a clone of Sierra's own interpreter. NAGI was created by disassembling the original AGI executable and writing equivalent C code that would run under SDL which is a free generic library for low-level access to graphics and audio.

Why do I need it?

Since it's a Windows program, NAGI doesn't depend on the hardware of the original IBM PC. If you have trouble running the original AGI games under Windows then NAGI might be helpful to you.

Symptoms with original AGI game:

  • Text is garbled (since the video card doesn't contain the appropriate font)
  • EGA/CGA do not display properly or you get a black screen
  • PC Speaker music does not work

Extra features with NAGI:

  • Mouse support for most games. You can control your character with the mouse.
  • Supports the 3 channel sound that's not possible with the PC Speaker.
  • Fake CGA support
  • You can play your games in a window instead of full screen.

How do I know if I have an AGI game?

Of all the AGI games I have encountered, they all follow a few basic file name arrangements.

  • Version 2 - object, words.tok, logdir, picdir, viewdir, snddir, vol.X
  • Version 3 - object, words.tok, <GAMEID>dir, <GAMEID>vol.X
  • Amiga Version 3 - object, words.tok, dirs, vol.X

Where <GAMEID> is replaced by the game's actual id (eg "KQ4" for Kings Quest 4).

The original Sierra interpreter used these files and are not used by NAGI:
agi, sierra.com, agidata.ovl, cga_graf.ovl, ega_graf.ovl, hgc_font, hgc_graf.ovl, hgc_objs.ovl, ibm_objs.ovl, jr_graf.ovl, vg_graf.ovl
They can be safely deleted or moved to another directory to save space.

Sierra also has a later interpreter called SCI. NAGI does not run these data files but FreeSCI does! You can pick out these files because they follow the format:
resource.XXX, resource.map

How do I install NAGI?

You need to download TWO files: NAGI and the SDL Library which NAGI depends on. Both of these can be found at the NAGI download section.

Unzip both these files (NAGI and SDL) into the same directory like C:\NAGI\

By default NAGI will look in the current directory and one directory level up to search for games. so if you wish, install your games like this:


and then run n.exe from c:\nagi. NAGI will display a menu of all detected agi games.

I run Windows NT, 2000, XP and I have trouble running NAGI.

Edit nagi.ini and go to the [sdl] section (should be at the bottom). Change "drv_video" or "drv_sound" to it's alternative values. These should be available in the ini file as well.

I run NAGI and I get an "the dynamic link library SDL.dll could not be found" error

You need to make sure NAGI and SDL have been installed in the same directory. Alternatively, you could make sure SDL.DLL is in c:\windows\system.

How do I get fullscreen?

Edit nagi.ini. Go to the [vid] section. Change the value of "full_screen" to 1.

How do I try out the CGA mode?

Edit nagi.ini. Go to the [vid] section. Change the the value of "renderer" to "cga0", "cga1" or "ega". The "ega" option will give you back your 16 mode mode.

Are there any other AGI clones available?

Yes. There's Sarien which has been around a lot longer and has been ported to a plethora of platforms. Another clone is AGIL but this has been discontinued so work can be made on NAGI to port it to Linux.

Are there any sites I can visit to learn more about AGI?

AGI Messageboard - most people interested in AGI or have questions come here.
AGI Development Site - if you wish to create your own AGI game. Has a huge links page.
Sierra - the makers of AGI

NAGI - the homepage of NAGI.
NAGI Docs - Online docs for NAGI.
Sarien - the oldest AGI clone.
AGIL - Linux upstart 😀

sonneveld@hotmail.com - my email address if you have any more questions.

Do you have a hastily looked up Hitchhiker's quote?


"Arthur realized as he fell, giddily and sickeningly, that if he was going to hang around in the sky believing everything that the Italians had to say about physics when they couldn't even keep a simple tower straight, that they were in dead trouble, and damn well did fall faster than Fenchurch." - Life, the Universe and Everything

You can post this anywhere as long as you note that I'm the original author.


Last edited by Snover on 2002-08-10, 07:21. Edited 1 time in total.

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