: How did games run without CD disks once launched?

Question

Back when CD-ROM was a main thing, I remember that sometimes on games you could insert the CD, launch the game, and then remove the CD, the game would still run (I believe that was the case for Age of Empires 2 for example).

How was this possible?

In: 3

Answer 1

The game data was transferred to the hard disk. The only reason to still check for the disk was as a copy protection measure.