There are a number of different personal computers, but the term PC refers to the IBM personal computer or its clones. In the department the majority of personal computers are PCs. Most have relativley small internal disks and rely on ''disk servers'' provided over the network such as PPFSn to provide disk space. These disk servers have many TBs of hard disk. PCs are used for word processing and computer Aided Design (CAD) work and as terminals to access UNIX servers. They are also used to control and collect data from experimental hardware.