It is a quite big game: the main executable is 117KB, plus around 50 overlay files of 1.5 KB each for the different dungeons and cities, plus the graphics files. I guess it was even too big for the average PC hardware at that time, or it was a limitation inherited from the original Apple II version: When you want to cast a spell you have to enter the number of the spell from the manual, maybe because there was not enough memory to fit the names of the 94 spells into RAM. Apart from that and the limited graphics and the lack of sound, the internal ruleset is very complete. You have all kind of spells and objects, capabilities, an aging mechanism, shops, etc.. The usual stuff that you also see in today's RPGs.
The modern uninstall.exe that came with it (I bought the game on GOG) was 1.3MB big.