Microcomputers :- A microcomputer is a small computer that is used by one person at a time. The desktop computers that you you see in  most offices, schools, colleges, and homes are microcomputers. They are also called personal computers or PCs.
Mainframe computers :- Mainframe computers are big, powerful, and expensive multiuser computers. They are mainly used for bulk data processing in large organizations like governments, airlines, and banks. The IBM zEnterprise and Unisys ClearPath are examples of mainframes. 

Mainframe computers have been produced by companies such as IBM and Unisys since the 1950s. At that time, they were large enough to occupy an entire room. As of 2014, mainframe computers are about the size of a refrigerator and cost at least $75,000. Corporations justify the expense by keeping mainframes running around the clock to handle critical tasks such as processing credit card transactions and updating airline information.

Microcomputers are smaller computers that derive their power from microprocessing chips. More commonly called personal computers, they are the most widely used type of computer in 2014. PCs include desktop computers, which are set up on a desk or similar surface and are rarely moved from one location to another. In contrast, a laptop is a portable computer with a clamshell design that allows the display screen to be folded over the keyboard. Tablets and smartphones are also intended for mobile use, but are smaller and more lightweight than laptops.