Output Devices. Printers

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 and design. We will classify printers as character printers, line printers and page printers in order to identify three different approaches to printing, each with a dif­ferent speed range. In addition, printers can be described as ei­ther impact or non impact. Printers that use electromechanical mechanisms that cause hammers to strike against a ribbon and the paper are called impact printers. Non impact printers do not hit or impact a ribbon to print.

Character printers print only one character at a time. A type­writer is an example of a character printer. Character printers are the type used with literally all microcomputers as well as on computers of all sizes whenever the printing requirements are not large. Character printers may be of several types. A letter-quality printer is a character printer which produces output of typewriter quality. Letter-quality printers typically have speeds ranging from 10 to 50 characters per second. Dot-matrix print­ers form each character as a pattern of dots. These printers have a lower quality of type but are generally faster printers than the letter-quality printers — in the range of 50 to 200 characters per second. One of the newest types of character printer is the ink-jet printer. It sprays small drops of ink onto paper to form print­ed characters. The ink has a high iron content, which is affect­ed by magnetic fields of the printer. These magnetic fields cause the ink to take the shape of a character as the ink approaches the paper.

Line printers are electromechanical machines used for high-volume paper output on most computer systems. Their print­ing speeds are such that to an observer they appear to be print­ing a line at a time. They are impact printers. The speeds of line printers vary from 100 to 2500 lines per minute. Line printers have been designed to use many different types of printing mechanisms. Two of the most common print mechanisms are

the drum and the chain. 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 no impact printers. Their print­ing rates are so high that output appears to emerge from the printer a page at a time. A variety of techniques are used in the design of page printers. These techniques, called electro photographic techniques, have developed from the paper copier tech­nology. Laser-beam printers use a combination of laser beam and electro photographic techniques to create printer output at a rate equal to 18000 lines per minute.

3 Answer the questions:

1. What are the three types of printers?

2. What is a letter-quality printer?

3. What is a dot-matrix printer?

4. What type of printer is the most common with microcomputer systems?

5. What is the most common printer type used on large com­puter systems?

6. What is an impact printer? Give an example.

7. What is a nonimpact printer? Give examples.

8. What are the most widely used printers?

9. How do you distinguish between a letter-quality printer and a dot-matrix printer?

10. Which of these printers is slower?

11. What types of character printers do you know?

12. How are printed characters formed by means of an ink-jet printer?

13. What are the main types of a line print­er? Which of them is faster?

14. What techniques are used in the operation of page printers?

4 Find English equivalents in the text:

Удобная для восприятия человека форма; наиболее ча­сто употребляемые устройства вывода информации; раз­личаться по рабочим характеристикам и внешнему виду; принтеры с посимвольной печатью; принтеры с построч­ной печатью; принтеры с постраничной печатью; различ­ные методы печати; диапазон скорости; принтеры контак­тные и бесконтактные; ударять по ленте; печатать по одному символу; буквально все компьютеры; а также; тре­бования печати; принтер с типографским качеством печати; точечно-матричные принтеры; струйные принтеры; разбрызгивать капли чернил; высокое содержание железа; магнитные поля; принимать форму символа; кажется, что печатают по строчке; барабанный принтер; цепочечные принтеры; лазерный принтер.

5 Translate these word combinations from English into Russian:

Approach: comprehensive approach; database approach; ed­ucational (training) approach; general approach; graphic ap­proach; self-study approach; step-by-step approach; trial-and-error approach.

Performance: application performance; computer perfor­mance; device performance; disk performance; display perfor­mance; error performance; execution performance; memory performance; network performance; processor performance.

Printer: black-and-white printer; color printer; character (at-a-time) printer; dot-matrix printer; graphical (image) printer; impact printer; ink-jet printer; laser printer; letter-quality print­er; matrix printer; network printer; page (at-a-time) printer.

Technique: advanced technique; analog technique; comput­ing technique; display (video) technique; formatting technique; hardware technique; measuring technique; modeling (simula­tion) technique; multimedia technique; numerical technique; programming technique; scanning technique; software tech­nique; testing technique.