3. Input-Output Environment. 1188

Data and instructions must enter the data processing system, and information must leave it. These operations are performed by input and output (I/O) units that link the computer to its external environment.

The I/O environment may be human-related (as a remote banking terminal) or human-independent (as a printer that produces output in a human-readable format).

Input-Output Interfaces.

Input devices provide a computer with data from a keyboard in a manner similar to typing or by a bar-code scanner.

Then data is transformed into the binary codes that the primary memory of the computer is designed to accept.

This transformation is accomplished by units called I/O interfaces or channels or input-output processors (IOP).

Input-output devices are classified as high-speed, medium-speed, and low-speed. The major differences between devices are the media that they use and the speed with which they are able to transfer data to or from the primary storage.

The high-speed devices are entirely electronic. The low-speed devices operate mechanically at the speed of a human operator. The medium-speed devices are more complex than the high-speed devices but not as complex as the low-speed.

bar-code scanner

– устройство считывания штрих-кода

4. Printers. 1381

Printers provide information in a permanent, human-readable form. They are the most commonly used output devices and are components of almost all computer systems. Printers vary greatly in performance, design and speed.

Printers may be either impact or nonimpact. Impact printers use electromechanical mechanisms that cause hammers to strike against a ribbon and the paper. Nonimpact printers do not hit or impact a ribbon to print.

Character printers print only one character at a time (as a typewriter). They are used in all microcomputers as well as in computers of all sizes whenever the printing requirements are not large.

Line printers are electromechanical machines used for high-volume paper output on most computer systems. They are impact. Their speeds vary from 100 to 2500 lines per minute.

Drum printers use a solid, cylindrical drum, rotating at a rapid speed. Speeds of drum printers vary from 200 to over 2000 lines per minute.

Chain printers have their character set on a rapidly rotating chain called a print chain. Speeds of chain printers range from 400 to 2400 lines per minute.

Page printers are high-speed nonimpact. Their print­ing rate is a page at a time. They are based on electro-photo­graphic techniques.

Laser-beam printers use a combination of laser beam and electrophotographic techniques to create printer output at a rate equal to 18000 lines per minute.

impact printer - контактный принтер

nonimpact printer - бесконтактный принтер

character printer - принтер с посимвольной печатью

page printer - принтер с построчной печатью

laser-beam printer - лазерный принтер

5. Mainframe Computers.

Part I. 1431

Mainframes (often called Big Iron) are powerful computers used mainly by large organizations for critical applications, typically bulk data processing such as census, statistics, enterprise resource planning, and financial transaction processing.

The term originally referred to the large cabinets that housed the central processing unit and main memory of early computers. Historically, mainframes acquired their name in part because of their substantial size, Most large-scale computer system architectures were firmly established in the 1960s.

There were several minicomputer operating systems and architectures that arose in the 1970s and 1980s, but minicomputers are generally not considered mainframes.

Many defining characteristics of "mainframe" were established in the 1960s, but those characteristics continue to expand and evolve to the present day.

Modern mainframe computers are highly available, reliable and secure, have extensive input-output facilities, compatibility with older software, and high utilization rates. These machines often run for years without interruption, with repairs and hardware upgrades taking place during normal operation.

In the 1960s, most mainframes had no interactive interface. They accepted sets of punched cards, paper tape, and/or magnetic tape. Teletype devices were also common, at least for system operators. By the early 1970s, many mainframes acquired interactive user interfaces.

census - перепись

bulk data processing - обработка больших объёмов информации

6. Mainframe Computers.

Part II. 1170

Several manufacturers produced mainframe computers from the late 1950s through the 1970s. Nearly all mainframe computers have the ability to run (or host) multiple operating systems, and thereby operate not as a single computer but as a number of virtual machines. In this role, a single mainframe can replace dozens or even hundreds of smaller servers.

Mainframes are designed to handle very high volume input and output (I/O). Compared to a typical PC, mainframes commonly have hundreds to thousands of times as much data storage online, and can access it much faster.

In the late 1990s new uses were found for mainframes as the price of data networking collapsed in most parts of the world.

Another factor currently increasing mainframe use is the development of the Linux operating system in 1999. Linux allows users to take advantage of open source software combined with mainframe hardware.

Mainframes are used to solve exceptionally difficult computing problems. They provide unified, extremely high volume online transaction processing databases for 1 billion consumers across multiple industries (banking, insurance, credit reporting, government services, etc.).