1. mainframe 3, notebook 5. PC

2. laptop 4. handheld 6. sub notebook II, Read the text

3. "Types of computer"

There are different types of computers. They are Mainframe, Personal Computer and Portable Computer. Let's consider them.

Table personal computer, supporting one workplace, is the most numerous group of the personal computers. Before appearance of portable personal computer the words «table» and «personal» were synonyms. Table personal computer often called computers for a workplace or office computers (although nowadays office personal computer is frequently called the work stations). A majority of home computers is also table. Those and others have practically identical characteristics: 32- and 64-bit architecture and circuit organization of the system, they used standard hardware and software. Most of the table personal computers belong to (wo large groups: IBM-compatible personal computer and personal computer Apple Macintosh. Table personal computers, oriented to a great number of users, are the absolute leaders of sales in computer industry, because of a small size and moderate price, their possibilities in most cases are sufficient for the decision of the most various (asks in an office, on production, in the way of living. Table personal computer has a system block, containing the power source, system board with a processor, hard disk, disk drives, monitor, keyboard and mouse. Fax, modem and other peripheral devices can be connected to them. Office personal computer is intended mainly for work in a network, Home personal computers,

not intended for work in a network, the communications are supported over the Internet. Calculations are accomplished by central processing unit. Central processing unit consists of two parts. Control unit receives the commands of the programs and organizes their implementation. The arithmetic-logic unit executes the calculations. Information is kept in different data storages.

The first portable computers produced by the company of Adam Osborn were named Portable and weighed about 10 kg. At weight of 4-5 kg they began to be named as Laptop. «Becoming» thinner on a pair of kilograms, similar machines began to be named as notebooks and their lighter variants as subnotebook. The smallest and the lightest (with weight of less than one pound, that is approximately 450 r) computers are called Palmtop or HPC (Handheld PC). Notebooks and subnotcbooks are the most widespread portable computers. A border between them is very conditional. It is usually considered, that weight of a notebook rangers from 2.2 to 4.5 kg, and subnotebook is from 0.9 to 2.7 kg. The overall sizes of notebook make 50x279x215 mm usually, and subnotebook is 38x254x190 mm. The size of screen matrix of modern notebook is from 11.3 to 15 inches, and subnotebook is from 6.4 to 11.3 inches. A notebook usually excels a subnotebook on the maximal size of the set main memory and hard disk capacity, although all depends on the class of a machine. As a rule, a subnotebook has external drives for floppy-disks and CD-ROM, while at notebooks they are usually built-in. For notebooks and subnotebooks Windows 95/98 is the basic operating system due to its ability to recognize setting and deleting of the PC Card devices without the restart of the machine. The computers-notebooks equipped with ionic-lithium accumulators provide the greatest time of autonomous work. The Nickel-metallhydrogen accumulators gradually become obsolete.

Keyboards of portable computers though have a smaller number of the keys but usually they emulate them. Touchpad is mainly used as the indicatory device in notebooks.

The work station (Workstation) differs from the ordinary table personal computer by a greater power and, accordingly a higher price. It takes one working seat and differs slightly from the personal computer. Many work­stations work in the operating system UNIX. Company of Microsoft offers the operating system Windows NT, which can co-operate on networks with other operating systems Microsoft, Apple Macintosh and with UNIX-similar systems. Work stations are used for intensive calculations. It ordinary works with the professional scientific and engineering appendixes of the type CAD design, creation of habitat, software and different appendixes like client-server. There are specialized graphic work stations for work with three-dimensional graphic arts. Presently the work stations of offices and enterprises are usually incorporated in local networks. The modem network work stations are usually equipped with facilities of remote administration, which allows the administrator of the network to produce reconfiguring of the work stations or setting new programs on them in the distance. The Work stations frequently

contain the specialized technological decisions promoting their reliability and price. For example, the last models of office machines are equipped with SMART-Hard disk.