I think ruling the CPU isn't exatly the way to describe this classes, since even a mainframe type computer can have singe chip processors, and a micro can consist of a whole chip graveyard. But your Note leads a trace: try the design goal as class. So, a mainframe is a general purpose computer specaly designed to transport, merge and modify data like a big steel plant modifies iron. Using only a small number of programms but serving the same task a _huge_ mass of users. Usualy these are just /370ish designs. A Mini is some kind of 'big' computer designed to serve a lot of people in an individual sense, giving every user (and sometimes even every single programm) the feeling of a complete independant computer. The OS is wasing a lot of resouces (not needed on mainframes) to ensure coexistence, fast programm change etc. The OS is mostly unix-like. A Workstation is 4M (you just missed the Megabucks :). A workstaton serves the needs of only one user. The OS is in most cases very graphic-able orientated. An average PC is just a workstation on a lower level, running several different application (maybe even at the same time) to serve every person as his own computer like a mini, but without sharing anything. The OS is almost complete graphic orientated. I think this sceme is sufficient for all GPC. If you miss the micro, its just because it represents no class of its own. The micro can be just a very small mini, or he is a PC(Workstation). Didn't the Wozniak once state that every micro before the A2 was just a small singe user mini ? Gruss H. -- Ich denke, also bin ich, also gut HRK