Computers are machines, or tools, that have been designed to make our lives easier. The physical items that you can touch, the monitor, central processing unit, and keyboard, are called hardware. Hardware makes up 1 part of a computer system. Mainframes are very large, expensive systems that are kept in special rooms with closely watched environmental conditions. You might use a mainframe for computing at a district or state level.
Many people can access a mainframe at one time.
A minicomputer is a smaller system that can serve fewer numbers of people. You might use a minicomputer in your school. The most popular type of computer system is the microcomputer or personal computer. The PC is what we see on everyone's desk. PCs are typically used by 1 person or small groups at a time.