The Alt Cheats are a debugging tool used in the Ultima 6 engine (i.e. they exist in Ultima 6, The Savage Empire and Martian Dreams). In Ultima 6 they were left in the game, so they became a popular cheat. However, they were disabled in the Worlds of Ultima Series.
F-15 Dragon later wrote a program called MDHack to enable the Alt Cheats in Martian Dreams. It also works for The Savage Empire. MDHack can be downloaded from:
There's a specific bit in the SAVEGAME\OBJLIST file that toggles cheating. It's the second bit from the left (i.e. 0100 0000 in binary) of byte 18f2 (hex), so if you open the file in a hex editor, look for the row starting at 18f0 (hex), and from there it's the second bit of the third byte (see screenshot above).
What MDHack does is set the entire byte to 40 (hex, 0100 0000 in binary), enabling the specific bit in question but turning off all the rest. In order to preserve the value of that byte (e.g. 03 hex, or 0000 0011 binary, in the screenshot above), you should instead take that value and OR it with 40 hex (e.g. 03 hex OR 40 hex = 43 hex).
You can activate a cheat by pressing Alt and typing the 3 numbers corresponding to that cheat, on the keypad. You need MDHack to be able to use them. The following links tell you which cheats exist:
The following are the debugging commands (cheats) you can use.
Ignore the Alt codes listed in the MDHack documentation, as many of them are either wrong or simply don't work.
I have also investigated the nature of these Alt codes and wrote a text file about Alt codes [TXT] which describes what Alt codes really are, and lists all the existing ones.
Character lists can be found:
Talk to Triolo and say "cheat". This will allow you to generate specific quest items, any other item, and edit flags. For a list of items, see the following links (in descending order of completeness):