Basically; it held the Cat OS and software in ROM, so it could boot immediately and run without disk access. If you recall, the Mac had most of its key OS funct

Basically; it held the Cat OS and software in ROM, so it could boot immediately and run without disk access. If you recall, the Mac had most of its key OS functions held in ROM for the same reason, although it couldn't fit its entire system in firmware. As a curious aside, everything except the core Cat OS was written in Forth, though you could also script functions through AppleBASIC (itself implemented in ROM on the motherboard). Kind of a neat little historical appendage; if Jobs hadn't booted Raskin from the Mac team, the Mac might well have ended up looking like this.