Early computers were all mainframes. They took a long time to build and were difficult to repair if they broke down. Each part had to be wired separately to other parts. Then, in the 1960s, everything changed. The integrated circuit was developed. The integrated circuit could combine thousands of electronic parts in one small piece. So smaller computers could be built. These minicomputers were about the size of a cupboard. Minicomputers have smaller memories than modern mainframes, but they are far more powerful.
Minicomputers cannot store as much data as mainframes but are more powerful than microcomputers.
The next step forwards came in 1971 when an American company made the first microprocessor. This is a type of integrated circuit that combines thousands of different parts in one small unit. Soon, microprocessors were being used in personal computers, or microcomputers, which were small enough to fit onto a desk. Chips made it possible for millions of people to have pocket calculators and computers at home.
Microcomputers have smaller memories than minicomputers or mainframes, but they can be connected to extra equipment.
Personal computers cannot do as much work, or do it as quickly, as mainframes or minicomputers. But they work hard and fast enough for the needs of most people using a computer at home, at school or in a small office.