This short piece by Umberto Ecco is a bit of an inside joke (you have to be old enough to remember using MS-DOS). Also, it makes more sense when you are surrounded by Renaissance art.
The fact is that the world is divided between users of the Macintosh computer and users of MS-DOS compatible computers. I am firmly of the opinion that the Macintosh is Catholic and that DOS is Protestant. Indeed, the Macintosh is counter-reformist and has been influenced by the ratio studiorum of the Jesuits. It is cheerful, friendly, conciliatory; it tells the faithful how they must proceed step by step to reach — if not the kingdom of Heaven — the moment in which their document is printed. It is catechistic: The essence of revelation is dealt with via simple formulae and sumptuous icons. Everyone has a right to salvation.
DOS is Protestant, or even Calvinistic. It allows free interpretation of scripture, demands difficult personal decisions, imposes a subtle hermeneutics upon the user, and takes for granted the idea that not all can achieve salvation. To make the system work you need to interpret the program yourself: Far away from the baroque community of revelers, the user is closed within the loneliness of his own inner torment.