1.Supercomputers are the most powerful type of computer.These machines are special high-capacity computers used by very large organizations. Fujitsu's K computer is one of the fastest computers in the world.
Mainframe computers occupy specially wired, air-conditioned rooms. Although not nearly as powerful as supercomputers, mainframe computers are capable of great processing speeds and data storage.
Minicomputers also known as midrange computers, are refrigeratorsized machines, medium-size companies or departments of large companies typically use them for specific purposes.
Microcomputers are the least powerful, yet the most widely used and fastest-growing type of computer. There are six types of microcomputers:desktop, media center, notebook, tablet PC, netbook, and handheld computers.

2. Microcomputers are the most common type.

3.Six types,desktop, media center, notebook, tablet PC, netbook, and handheld computers.