Components became smaller and the system became less expensive to build.
Modern digital computers are all conceptually similar, regardless of size and shape. Nevertheless, they can be divided into several categories on the basis of cost and performance.
The first one is the personal computer or microcomputer, a relatively low-cost machine, usually of desk-top size. Sometimes they are called laptops. They are small enough to fit in a briefcase. The second is the workstation, a microcomputer with enhanced graphics and communications capabilities that make it especially useful for office work. And the server computers, a large expensive machine with the capability of serving the needs of major business enterprises, government departments, scientific research establishments. The largest and fastest of these are called supercomputers.
A digital computer is not actually a single machine, in the sense that most people think of computers. Instead it is a system composed of five distinct elements: a central processing unit, input devices, memory storage devices, output devices and a communications network, called a «bus» that links all the elements of the system and connects the system itself to the external world.
Talking about a central processing unit or the heart of computer; I would like to add that there were several generations of microprocessors. The first generation was represented by processing unit Intel 8086. The second generation central processing unit was represented by processing unit Intel 80286, used in IBM PC AT 286. In the end of 80s such computer costs about 25-30 000 rubles in the former USSR. The third generation is represented by Intel 80386, used in IBM PC AT 386. The microprocessors of the fourth generation were used in computers IBM PC AT 486. There are also central processing units of the fifth generation, used in Intel Pentium 60 and Intel Pentium 66, central processing units of the sixth generation, used in computers Intel Pentium 75,90,100 and 133. Few years ago appeared central processing units of seventh and eighth generations.
Computer speeds are measured in gigahertz today. Recently, an optical central processing unit has been invented, which is capable of executing trillions discrete operations per second or it is as fast as the speed of light.