английский принтеры (текст про принтеры с каких-то старых бумажек. Только текст. С него требуют перевод)

Printed output, which can be read by humans rather than by a computer, is most common output. It is two-dimensional. Consisting of characters within a line, and lines on a page. One of the most difficult parts of printing output is the reaction of the user to the printed page, because somehow the printed output produces a response from the reader much like that of people to a roomful of new furniture. They have definite ideas where each piece should go, but after seeing it there, they are apt to change their minds. The same occurs when the reader first sees the printed output of a report, for instance.

No matter how simple or complex the data-processing operation is, the final results must be made available in a form usable by humans, and usually in the form of a permanent record. This is the purpose of the printers used with computing equipment.

Printers vary in speed, size, and cost, and are designed to meet printing requirements ranging from roughly the speed and volume of the typewriter up to thousands of lines per minute. There are two ways of printing: by impact (striking a character through a carbon, like a typewriter) or non-impact (photocopying, like an office copier). Impact printers are generally a drum, or a chain or train. The drum has a spinning cylinder for each character position in a line, and each cylinder contains all the character in a character set. As each cylinder spins into the appropriate character position, it is hammered onto the paper through a carbon ribbon. Drum printers generally give the lowest quality printing, because it the hammer hits a little early or late, the character will appear slightly above or below the line. This is noticeable on printed line, giving it a wary appearance.

In train or chain printers, the character move laterally across the page, and as the proper character moves into position, it is hammered onto the pages through a carbon ribbon. If the hammer hits a little early or late, the character will appear slightly to the right or left of its proper position, but variations in horizontal spacing are not so noticeable to humans.

Other types of impact printers are the daisy wheel printer, the matrix printer, and the line printer. The daisy wheel printer uses a wheel with up to 100 characters, each being on an individual arm, so that only rotation is needed. The hammer hits a single letter, guaranteeing a accurate positioning and uniform striking. This allows a fast, quiet, and reliable operation, with super print quality.

A matrix printer, on the other hand, uses pins to print a pattern of dots on paper. The characters are generated by selecting the appropriate combinations of pins in a rectangle of 5 rows by 7 columns or 9 columns. Each pin is equipped with a coil, which, when energized, throws the pin against the ribbon, printing a dot on the paper. For each character, seven of nine lines of dots have to be printed, however, the inertia is minimal, so fast operation is possible. The general advantages of using matrix printers are relative low cost, high speed, and quiet operation. The Main disadvantage is the relatively poor quality of printing, which is sufficiently good for the eye, but not for reproduction or for business letters.

Finally, the printing mechanism in line printers is completely different from matrix printers. In the line printer, the character set to be printed is on a cylinder where each segment has the full set of characters in raised form around its edge. All segments are aligned with one another; that is, all the ‘As’, for example, are in line. Whenever the printer is in print mode, the cylinder is rotating and each character in the set passes by the line to be printer as one complete revolution of the cylinder is made. The printer times the movement of a print hammer so that the character on the cylinder segment is brought into contact with the ribbon and paper. One complete line of characters is printer during one revolution of the cylinder. It is interesting to note that all the ‘As’ used in the line are printed first, then all the ‘Bs’, and so on until finally all the letters that make up the words have been printed and the line is complete. Whereas 200 to 600 lines per minute maximum are produced by the other printers, a line printer will operate up to 3000 lines per minute.

There are several types of non-impact printers called thermal and electrosensitive printers (electrostatic printers). These printers use a special chemically treated paper and expose characters onto it by some means such as a laser. The characters are then fixed onto paper by heating it. Because the printing element is simple and has no the moving parts, these printers are inexpensive and silent. These newer devices are also much faster and allow any character set to be used. In addition to drawing lines and shading, light can be flashed through a translucent slide to expose a drawing onto the paper. Very fast non-impact printers are capable of rates up to 13360 lines per minute.

In the largest computer installations, where cost is no longer a consideration, non-impact printers are used for very high speed. An ink jet printer operates by projecting small ink droplets and deflecting them electrostatically. Speeds of 40000 lines per minute may be achieved. In the laser writer, the paper is charged electrostatically and attracts dry ink powder, as in a Xerox machine. The pattern is then baked in the paper. Many lines are printed simultaneously, and speeds of 20000 lines per minute can be attained.

Multiple copies of output are often required, and can be produced either by printing the report several times or by using multipart paper, which consist of layers of paper separated by carbon sheets. However, non-impact printers cannot use such multipart paper.

Microfilm is often used as an alternative to the printer. The output is “printed” on microfilm rather than paper, which, in addition to being faster, also condenses large stacks of paper down into small amounts of microfilm with no special programming. The drawback of computer-output microfilm (COM) is that it takes a special device to print the microfilm and a special viewer to read it.