We'd have one person reading the magazine, one person typing, and one person making sure that the typist typed what the reader read. We could "install" a game in just a few hours that way!
Even if you're not an old-timer who was around for this era of computing, you may well enjoy seeing what was involved in getting a _program_ running in that era — or checking out the fully-working version of the game that is embedded in this piece. (There is, of course, a little Prince detour, too.)