What map ???
TELENGARD's dungeons are not random. You can go to any spot, on any level, and take note of it's features. Is there a fountain there, maybe a staircase a few steps away, or a throne in the next room? Next time you visit, it'll be the same. There are 50 levels of Telengard, each on a 200x200 grid. That's 40,000 areas per level - 2,000,000 for the whole dungeon.
So how does a small BASIC program keep track of that vast dungeon? Well nobody sat down and drew this out on graph paper and then transcribed it into the program. The computer computes, based on your location, your exact surroundings. It is always the same if you are in the same spot. This can lend a familiarity to the game, as you can learn to navigate certain areas of certain levels. This gives the game a much more familiar feel than if it randomly computed, and constantly changed, your surroundings. You've got more control this way (until you get teleported)!
There's nothing quite like starting out on Level 1, teleporting
down to Level 50, and somehow surviving long enough to grab a powerful
magic item and return to Level 1. Somehow those monsters don't have much
of a chance against your new Sword +200! Of course, chances are you wouldn't
survive such a treacherous journey...