Contacts 

The main parameters of laser printers are not included. Abstract: Printers, their characteristics and functionality. What will we do with the received material?

A dot matrix printer produces characters using several needles located in the printer head. The paper is pulled in by a shaft, and an ink ribbon is placed between the paper and the printer head. Currently, matrix (needle) printers are used less and less. The advantages of these printers: satisfactory printing speed and versatility, which consists in the ability to work with any paper, as well as the low cost of prints. Disadvantage: low quality of printed products, especially graphics. Color printing is not possible. Another disadvantage: a needle printer is a mechanical device, and the operation of mechanical components is always accompanied by noise.

Inkjet printers

In inkjet printers, the image is formed by microscopic drops of special ink that fly out onto the paper through small holes. Piezocrystals are used as elements that push out ink jets (Fig. 2.9).


Rice. 2.9.

Laser printers

Laser printers currently provide best quality print. However, color laser printers are very expensive, so laser printers usually print in black and white. Black-and-white laser printers use a computer-controlled laser beam to print (Fig. 2.10).


Rice. 2.10.

Go to main parameters laser printers relate:

  • resolution, dpi (dots per inch - dots per inch);
  • performance (pages per minute); Laser printers with average capabilities print 6–10 pages per minute. High-performance network laser printers can print up to 20 pages per minute or more. Of course, these are arbitrary figures, since on the same printer printing complex graphic images will take much longer than printing text;
  • paper size used. Most laser printers can print on A4 paper, less often A3;
  • the amount of your own RAM. A laser printer processes entire pages, which involves a lot of calculations. The most common memory used in black and white laser printers is from 2 to 16 MB.

Scanners

New term

Scanner- a device for copying graphic and text information for the purpose of entering it into a computer. There are three types of scanners - handheld, flatbed and drum.

Handheld scanners- These are relatively inexpensive devices of small size. You often see them in stores, at the checkout. They serve there to read the barcode with the price of the product. The disadvantages of a hand-held scanner include the dependence of scanning quality on the user’s skills and the inability to scan relatively large images entirely.

IN drum scanners the source material is fixed on the cylindrical surface of a drum rotating with high speed. Devices of this type provide the highest resolution in the range of 2400–5000 dpi. Currently, drum scanners are used mainly in the printing industry.

Most often used for home users and offices flatbed scanners(Fig. 2.11).


Rice. 2.11.

Flatbed scanners are designed to input graphic information from transparent or opaque sheet material. Their standard format is A4, so not only a separate sheet or page, but also a whole unfolded book or magazine can be placed under the cover of such a scanner “face” on the glass. In this way, flatbed scanners resemble copiers. The main elements of the scanner are a semiconductor laser and a semiconductor photodetector.

The principle of operation of these devices is that a beam of light reflected from the surface of a material (or transmitted through a transparent material) is detected by special elements called charge-coupled devices (CCDs). When the scanner is guided over text or an image, a laser beam runs across the sheet, scans it and reflects it onto a light-sensitive semiconductor element. A photocell converts the light signal into an electrical signal, which is then transmitted via a bus to the computer. In it, the signal is converted into a digital form containing information about the coordinates and color of each pixel in the image. And finally, at the last stage, the obtained image information is written to disk as a file.

Scanner Specifications

In order to choose the right type of scanner, and accordingly make the most of its capabilities to implement the assigned tasks, you need to understand technical specifications scanners and existing terminology.

  • Resolution is the main characteristic of a scanner. During the scanning process, the image is divided into individual points, the size of which is determined by the characteristics of the optical system and photocells. Optical resolution refers to the number of such points that fit on a segment of a certain length. The device specifications may indicate different horizontal and vertical resolutions. For example, the parameter 300?600 dpi means that each square inch of the image is divided into 300 pixels horizontally and 600 vertically. The higher the resolution, the more information about the original can be entered into the computer and processed further.
  • Scanner performance is characterized by the duration of scanning a sheet of standard-sized paper and depends both on the perfection of the mechanical part of the device and on the type of interface used to interface with the computer. Basic models often use scanner communication via a USB port. In professional scanners - SCSI.
  • The dynamic range of a scanner is determined by the logarithm of the ratio of the brightness of the lightest areas of the image to the brightness of the darkest areas. A typical reading for office scanners is 1.8–2.0, while for professional scanners it is between 2.5 (for opaque materials) and 3.5 (for transparent materials).
  • The scanner's color depth reflects the bit depth of the analog-to-digital converter, that is, it is a characteristic that shows how accurate the color information is for each point of the scanned image. A color depth of 1 bit corresponds to the black and white operating mode of the scanner; each point can only be black or white. In gray mode, the color depth is usually 8 bits. This corresponds to 256 shades of gray. This is the number of shades possible for each point. Color scanning is nothing but scanning in gray mode with different filters (red, blue, green). 256 shades for each component of the three give a total of 16.7 million possible color combinations (24-bit image). It would seem that 24 bit is enough to accurately convey any shade, but with further adjustments to gamma, brightness or contrast, the size of the palette decreases significantly, especially at the edges of the spectrum, and some of the data is lost. It is for this reason that leading manufacturers are already releasing models with a color depth of 36 and even 48 bit. In the event of inevitable data loss, the "spare" bits allow a true 24-bit image to be obtained.

Mouse

A mouse is a control device that is small device with two or three buttons. Moving the mouse on a flat surface is synchronized with the movement of a graphic object (mouse pointer) on the monitor screen. This device requires special support system program- mouse drivers.

The driver is installed either when you connect the mouse for the first time, or when installing the computer's operating system. The mouse driver is designed to interpret the signals coming through the connection port. In addition, it provides a mechanism for communicating information about the position and state of the mouse to the operating system and running programs. The computer is controlled by moving the mouse along the plane and briefly pressing the right and left buttons. Unlike a keyboard, a mouse cannot be directly used to enter character information - its control principle is event-based. Mouse movements and mouse button clicks are events from the point of view of its driver program. By analyzing these events, the driver determines when the event occurred and where the pointer was located on the screen at that moment. This data is transmitted to application program, with which the user works in this moment. A standard mouse has only two buttons, although there are custom mice with three buttons or two buttons and one rotary control. Adjustable mouse parameters include: sensitivity (expresses the amount of movement of the pointer on the screen for a given linear movement of the mouse), left and right functions. right buttons, as well as double-click sensitivity (the maximum time interval at which two mouse clicks are treated as one double click). In modern computers that use a window interface built on event processing, the absence of this device can lead to a complete blocking of work on the computer.

Based on the principle of operation, there are matrix, laser, LED and inkjet printers. Dot matrix printers - simple printing devices. The principle of their operation is that data is displayed on paper in the form of an imprint formed by the impact of cylindrical rods (“needles”) through an ink ribbon. The print quality of dot matrix printers directly depends on the number of needles in the print head. The most common are 9-pin and 24-pin matrix printers. The latter make it possible to obtain document prints that are not inferior in quality to documents written on a typewriter. The performance of dot matrix printers is assessed by the number of characters printed per second, cps (characters per second). The usual operating modes of dot matrix printers are: draft - draft printing mode, normal - normal printing mode and NLQ (Near Letter Quality) mode, which provides print quality close to the quality of a typewriter.



Laser printers provide high quality printing, not inferior to, and in many cases superior to, printing. They are also distinguished by their high printing speed, which is measured in pages per minute, ppt (page per minute). As in dot matrix printers, the final image is formed from individual dots. The operating principle of laser printers is as follows:

in accordance with the incoming data, the laser head emits light pulses that are reflected from the mirror and fall on the surface of the photosensitive drum;

areas of the surface of the photosensitive drum that received a light pulse acquire a static charge;

the drum, when rotating, passes through a container filled with a coloring composition (toner), and the toner is fixed to areas that have a static charge;

with further rotation of the drum, its surface comes into contact with the paper sheet, resulting in the transfer of toner to the paper;

a sheet of paper with toner applied to it is pulled through a heating element, causing the toner particles to sinter and stick to the paper.

The main parameters of laser printers include:

resolution, dpi (dots per inch, dots per inch);

performance (pages per minute);

paper size used;

the amount of your own RAM.

When choosing a laser printer, you must also take into account the print cost parameter, that is, the cost Supplies to obtain one printed sheet of a given format. Consumables include toner and drum, which lose their properties after printing a certain number of prints. Currently, the theoretical limit for this indicator is about 0.3-0.4 rubles. per page. In practice, mass-produced laser printers provide values ​​from 0.6 to 1.5 rubles. per page. The main advantage of laser printers is the ability to produce high-quality prints. Middle-class models provide print resolutions of up to 600 dpi, and professional models provide print resolutions of up to 1200 dpi.

Operating principle LED printers similar to the operating principle of laser printers. The difference is that the light source is not a laser head, but a line of LEDs. Since this ruler is located across the entire width of the printed page, there is no need for a horizontal scanning mechanism and the entire design is simpler, more reliable and cheaper. The typical print resolution for LED printers is about 600 dpi. The cost of a copy for LED printers is slightly cheaper than 0.4 rubles. per page. The disadvantage of these printers is the lower speed and reliability of these devices.

IN inkjet printers The image on paper is formed from spots formed when drops of dye hit the paper. The release of microdroplets of dye occurs under pressure, which develops in the print head due to vaporization. In some models, the drop is ejected with a click as a result of the piezoelectric effect - this method allows for a more stable drop shape, close to spherical. The quality of the printed image largely depends on the shape of the drop and its size, as well as on the nature of absorption of the liquid dye by the surface of the paper. Under these conditions, the viscosity properties of the dye and the properties of the paper play a special role. The positive properties of inkjet printing devices include a relatively small number of moving mechanical parts and, accordingly, the simplicity and reliability of the mechanical part of the device and its relatively low cost. The main disadvantage, compared to laser printers, is the instability of the resulting resolution, which limits the possibility of their use in black-and-white halftone printing. At the same time, today inkjet printers have found very wide application in color printing. Due to their simplicity of design, they are far superior to color laser printers in terms of quality/price. With a resolution above 600 dpi, they make it possible to obtain color prints that are superior in quality to color prints obtained by photochemical methods.

When choosing a printer, you should definitely keep in mind the parameter of the cost of printing one print and take into account that the cost of printing one print on them can be several times higher on laser printers (Fig. 18).

Rice. 18. Comparative efficiency of various printers

Laser printers provide high quality printing, not inferior to, and in many cases superior to, printing. They also feature high print speeds, measured in pages per minute. (ppm -page per minute). As in dot matrix printers, the final image is formed from individual dots

They use the electrographic method of image formation, which is used in copiers of the same name. The laser is used to create an ultra-thin light beam that traces the contours of an invisible dot electronic image on the surface of a pre-charged photosensitive drum - electric charge flows down from points illuminated by the laser beam on the surface of the drum. After developing the electronic image with dye (toner) powder adhering to the discharged areas, printing is performed - transferring the toner from the drum to paper and fixing the image on the paper by heating the toner until it melts.

The operating principle of laser printers is as follows:

§ in accordance with the incoming data, the laser head emits light pulses that are reflected from the mirror and fall on the surface of the photosensitive drum;

§ horizontal scanning of the image is performed by rotating the mirror;

§ areas of the surface of the photosensitive drum that received a light pulse acquire a static charge;

§ When the drum rotates, it passes through a container filled with a coloring compound (toner), and the toner is fixed to areas that have a static charge;

§ with further rotation of the drum, its surface comes into contact with the paper sheet, resulting in the transfer of toner to the paper;

§ a sheet of paper with toner applied to it is pulled through a heating element, as a result of which the toner particles are sintered and fixed to the paper.

The main parameters of laser printers include:

Resolution, dpi (dots per inch - dots per inch);

Productivity (pages per minute);

Size of paper used;

Amount of own RAM.

When choosing a laser printer, you must also take into account the cost of a print, that is, the cost of consumables to produce one printed sheet of standard A4 format. Consumables include toner and drum, which lose their properties after printing a certain number of prints. The unit of measurement is cent per page(meaning US cents). Currently, the theoretical limit for this indicator is about 1.0-1.5. In practice, mass-market laser printers provide values ​​from 2.0 to 6.0.



The main advantage of laser printers is the ability to produce high-quality prints. Middle-class models provide print resolutions of up to 600 dpi, and professional models provide print resolutions of up to 1200 dpi.

LED printers. The operating principle of LED printers is similar to that of laser printers. The difference is that the light source is not a laser head, but a line of LEDs. Since this ruler is located across the entire width of the printed page, there is no need for a horizontal scanning mechanism and the entire design is simpler, more reliable and cheaper. The typical print resolution for LED printers is about 600 dpi.

Laser printers provide the highest quality printing with a resolution of up to 50 dots/mm (1200 dpi) and print speeds of up to 1000 cps. Color laser printers are widely used. For example, the Tektronix (USA) Phaser 550 laser printer has a horizontal and vertical resolution of 1200 dpi; color printing speed - 5 A4 pages per minute, monochrome printing speed - 14 pages/min. The characteristics of some laser printer models are shown in Table 4.12.

Table 4.12.

Comparative characteristics of some Epson printers And Hewlett Packard

Advantages laser

printers:

The highest quality;

High performance;

Not high level noise.

Flaws laser

printers:

High price;

Large dimensions;

Requires quality service.


Printers can be connected via both parallel and serial ports. Parallel ports are used to connect parallel printers (receiving information one byte at a time). For example, adapters like Centronics allow you to connect up to three printers simultaneously. Serial ports (2 devices) are used to connect sequentially operating (perceiving information sequentially 1 bit at a time) printers, for example, RS-232C type adapters (connection C2). A serial printer does not mean it is slow. Most printers use parallel ports.

Many high-speed printers have their own buffer memory with a capacity of up to several hundred kilobytes. In conclusion, it should be noted that the most popular printers for personal computers (their share is at least 30%) are produced by the Japanese company Seiko Epson. The control language for these printers (ESC/P) has become de facto standard. Printers from Star Micronics, Hewlett Packard, Xerox, Mannesmann, Citizen, Panasonic, etc. are also widely used.

III. Multimedia devices

Current level of development computer technology had a huge impact on the process of creating and producing audio-visual materials. A revolutionary technological leap in the field of digital audio recording made it possible to replace bulky and expensive studios with a personal computer. The essence of this “revolution” is that if before everything technical issues processing of audio information was solved using large quantity devices, now these problems are quite successfully resolved by sound cards, boards and, accordingly, software.

Sound cards . Today, a device designed to input and output sound information into a computer is a sound card. Sometimes they are called “sound blasters”, “sound adapters”, but we will still focus on the concept of “sound card”.

What can a sound card do? Some believe that it simply provides music and sound accompaniment for computer games. However, in reality this is far from the case. Generally speaking, having even the most ordinary sound card, you have the opportunity to quite easily compose and direct radio programs, melodies, and provide signal processing. Yes, all this can be done in one way or another by the simplest sound card. Another thing is that for this it is often necessary to have specific programs, although not very complex, but not found widespread. This does not mean at all that these programs are intended only for professionals. It’s just that very often they are not widely used because their manufacturers are not always large companies, such as, for example, Microsoft, IBM, etc. It should be noted that software tycoon companies are not always as convenient as possible, and sometimes programs of generally unknown people literally make a revolution in certain areas. In addition, often ignorance of even the minimal capabilities of sound cards is due to the fact that the standard package operating systems Sound processing programs do not turn on.

Video capture cards . To work with a video image on a computer, it must be digitized or converted into a form that the computer can understand. For this, there are special capture cards that are inserted into the motherboard of your computer and allow you to input a video signal from an external source, convert it into an understandable format for the computer, compress this signal, and, ultimately, output the edited video clip back to the original or other equipment . Such equipment can be a video recorder, video camera and other media that reproduce and store video information.

The range of tasks solved by multimedia devices is expanding with the development of software and hardware computers. However, in almost any design there are devices such as:

n Analog-to-digital and digital-to-analog converters;

n Music synthesizer;

n Connectors for connecting a microphone and headphones (or an external amplifier), as well as the microphones and headphones themselves.

Many modern sound cards also have a number of other devices. Even just listing them shows how complex it is, and for many of us interesting thing- sound card:

n Signal processor for compressing audio information and implementing various effects;

n Read-only memory containing samples of synthesized sounds;

n Random access memory for temporary storage of instrument sound samples.

All these devices have recently become increasingly important, since the modern trend of computerization of all spheres of human activity seems to completely virtualize professional studios and facilities in the near future. This also affects the military sphere and the sphere of our professional activities.

IV. Communications and telecommunications

Modem. A device designed to exchange information between remote computers via communication channels is usually called a modem (MOdulator + DEModulator). In this case, the communication channel is understood as physical lines(wired, fiber optic, cable, radio frequency), how they are used (switched vs. dedicated), and how data is transmitted (digital vs. analog signals). Depending on the type of communication channel, transmitting and receiving devices are divided into radio modems, cable modems and others. The most widely used modems are those aimed at connecting to dial-up telephone communication channels.

Digital data entering the modem from a computer is converted in it by modulation (amplitude, frequency, phase) in accordance with the selected standard (protocol) and sent to telephone line. The receiver modem, which understands this protocol, performs reverse conversion (demodulation) and sends the recovered digital data to its computer. Thus, remote communication between computers and data exchange between them is ensured.

The main consumer parameters of modems include:

§ performance (bit/s);

§ supported communication and error correction protocols.

The volume of data transmitted per unit of time depends on the performance of the modem. The efficiency of interaction of a given modem with adjacent modems depends on the supported protocols (the probability that they will interact with each other when optimal settings). At present, only the ease of installation and configuration of the modem currently depends on the bus interface (in the future, with the general improvement of communication channels, the bus interface will begin to influence performance).

Codec - Software or hardware unit designed for compression/decompression (Compressor + Decompressor). Used to convert a signal to a form convenient for transmission over communication channels. Used in communication systems.

Devices of this type are connected to a special port available on computer motherboards .

Network adapters – hardware and software modules ensuring joint work geographically remote computers on one network under a single management and access to hardware and software resources networks.

Conclusion

The main trend in the development of computer technology at present is the further expansion of the scope of application of computers and, as a consequence, the transition from individual machines to their systems - computer systems and complexes of various configurations with a wide range of functionality and characteristics.

The most promising, created on the basis of personal computers, geographically distributed multi-machine computing systems – computer networks– focus not so much on computational information processing, but on communication ones information Services: email, teleconferencing systems and information and reference systems.

In the development and creation of computers themselves, heavy-duty computers—supercomputers and miniature PCs—have a significant and stable priority in recent years. Underway search work to create 6th generation computers based on distributed neural architecture - neurocomputers. In particular, neurocomputers can use existing network microprocessors - transputers (network microprocessors with built-in communications).

The widespread introduction of multimedia will make it possible to communicate with a computer in natural language, and multimedia cannot be interpreted narrowly, only as multimedia for a PC. This is already being facilitated by:

Emerging technologies of media servers capable of collecting and storing huge volumes of information and providing it in real time based on many simultaneously arriving requests;

Systems of ultra-high-speed broadband information highways that connect all consumer systems together.

Experts predict in the coming years the possibility of creating computer model the real world - a virtual system in which we can actively live and manipulate real objects. Many of the prerequisites for this already exist, but there are also problems. The most important of them is ensuring intellectual property rights and confidentiality of information.

Test questions and assignments

1. How do you see the dialectical nature of the relationship between software and hardware?

2. What elements does a canonical computer consist of?

3. What are the principles of program management?

4. What is a PC command? What are the main types of teams?

5. Describe the process of executing a command.

6. What are the main features of the computer classification?

7. What is a personal computer?

8. What are the main elements that make up a PC?

9. Name the main ones functional characteristics PC.

10. How does a PC system differ from its design?

11. What main elements does a microprocessor contain?

12. Name the main elements of the in-system machine interface. What are the peripheral devices of a personal computer?

13. What does a personal computer video system include?

14. What are the quality indicators of personal computer memory?

15. Describe the logical structure of main memory.

16. How are external storage devices classified?

17. What are the main information input/output devices?

18. What is the difference between the concepts: user interface, internal system interface?

19. Name and characterize the main elements of multimedia and communication equipment for a PC.

20. Study of system unit components.

Set the power supply locations;

Set location motherboard;

Set the nature of the connection between the motherboard and the power supply;

Set location hard drive;

Set drive locations floppy disks and disk drive CD-ROM;

Set location sound card and video adapter cards;

Learn how to connect your mouse. The mouse can be connected to a serial port or to a special port PS/2, having a round-shaped connector. Latest models can be connected to the keyboard via interface connectors USB.

21. Study of motherboard components.

Locate the processor and study the organization of its cooling system. Use the markings to determine the processor type and manufacturer;

Set the location of the connectors for installing RAM modules. Find out their number and type of modules used ( DIMM or SIMM);

Set the location of the slots for installing expansion cards. Find out their number and type ( ISA, VLB, PCI, AGP). Record their differences in shape and color.

22. Studying the order of starting a computer.

Turn on the monitor and computer system;

When power is applied, a message about the BIOS version appears on the monitor screen. To observe the messages, use the Pause/Break key. It pauses the download and allows you to read the message carefully. To continue starting, use the ENTER key.

Chapter 5. PC system software

§ 5.1. PC software

Personal computers, like computers of other classes, are a combination of hardware and software. Hardware (processor, memory, input/output devices, etc.) processes data according to certain programs. A set of programs forms PC software.

Ministry of transportation Russian Federation

Federal Agency for Railway Transport

State educational institution

higher professional education

Omsk State University communication lines

OmGUPS (CPMM)

Department of World Economy

Printers: their characteristics and functionality.

Thematic abstract

in the discipline "Informatics"

Student gr. 50b

Melnichenko K.L.

1. Introduction………………………………………………………………………………3

2. Characteristics of printers……………………………………………………….4

3. Classification of printers……………………………………………………………..6

3.1. Dot matrix printer…………………………………………………….8

3.2. Inkjet printer……………………………………………………….9

3.3. Laser printer……………………….………………….……..………….10

3.4. Sublimation printer………………….………….……….………11

3.5. Other printers…………………………………….………………….12

4. History and principle of operation…………………………………………………………….14

5. Conclusion………………………………………………………………………………...18

6. Bibliography……………………………………………………………19

Introduction.

A printer - peripheral device a computer designed to display information on a solid medium, usually paper. The word is borrowed from English. printer, from to print (“print”) + -er (“the one who performs the action”).

The printing process is usually called “printing”, and the resulting document is called a “printout” or “hard copy” (tracing paper from English hard copy).

Printers are designed to print on paper (create a “hard copy”) numerical, text and graphic information. According to their operating principle, printers are divided into matrix, inkjet and laser.

Characteristics of printers.

The main characteristics of printers include the following indicators:

Resolution is one of the the most important characteristics printer, measured in dots per inch (dpi).

· Printing speed - for inkjet printers usually does not exceed 3-8 pages of text per minute. If you print illustrations, the time spent per page increases several times, from 1 to 5 minutes per page. Laser printers have print speeds ranging from 7 to 20 standard printed pages per minute.

· Photo printing in color - the ability of an inkjet printer to print color illustrations. To do this, the printer must be equipped with a photo cartridge. There are printers that were originally designed for printing photographs, and quite often - directly from digital camera, without a computer. Currently, there is special photographic paper on sale, the quality of photographs printed on it is “several times” higher than usual.

· The amount of built-in (RAM) memory - for laser printers. The more memory, the faster the printing of texts and graphics. The typical value is from 4 to 8 MB, it is not always enough, but in some printers it is possible to increase the memory.

· Connecting printers to personal computer. Every modern computer is equipped USB port, therefore the printer must be selected with the same connection. By bus USB data are transmitted faster - this increases the printing speed.

· Printer compatibility (laser) - this is the Esperanto language for printers different manufacturers. Historically, professional-class printers support the PostScript language; personal (home) printers have full support for PostScript instructions - a rarity. Basically, they can only partially emulate PostScript, which is quite enough. But there is another language, PCL, which is the standard for most laser printers

· Paper feeding method. In modern printers, paper is loaded from the tray either from the top - this is a vertical feed, or from the bottom tray - a horizontal feed.

Classification of printers.

It is proposed to classify printers into five main positions:

· operating principle of the printing mechanism,

· maximum paper sheet size,

· use of color printing,

· the presence or absence of hardware support for the PostScript language,

Based on the printing principle, there are different types of dot matrix, inkjet and laser (page) printers. There are a number of other printing technologies, such as sublimation printing and thermal transfer printing, which are used much less frequently. Laser and LED technologies (in the latter case, instead of a laser and a mirror deflecting the laser beam, a line of LEDs is used) are in many cases indistinguishable from the point of view of the end user. The parameter that determines the print quality of laser printers is resolution.

The most common models are A3 and Legal formats (i.e., designed for a sheet of paper slightly larger than A4). Models that work with A3 paper are slightly more expensive. The ratio of sales of “narrow” and “wide” printers is gradually changing towards the former. Most A3 printer models use matrix or inkjet printing.

Based on the range of reproduced colors, printers are divided into black and white, black and white with a color printing option (such models are available among matrix and inkjet printers) and color. For color printers within the same type (inkjet), print quality varies very significantly from model to model. As a result, they are positioned differently on the market. Printers with a color option tend to have trouble reproducing pages that have color graphics next to a black background. The latter is obtained by mixing ink of several primary colors. As a result, the black color is not saturated enough, and the cost of printing such a page is very high.

For high-quality reproduction of illustrations stored in vector formats, it is important to have a built-in PostScript language interpreter. Formally, models that support the PostScript language are approximately 25% more expensive than similar models that do not include this option. However, to actually take advantage of the PostScript language, you have to purchase additional memory and the cost difference can be quite significant.

Based on printing speed, four groups can be distinguished: dot matrix printers without autofeed; printers providing print speeds up to 4 ppm. and intended for individual use; printers with print speeds up to 12 ppm, serving workgroups; powerful network printers with a productivity of more than 12 ppm. Printer performance is a significant factor for organizations where several people use one printer at once, and an indicator that has virtually no effect on consumer preferences when it comes to the individual use of a printing device.

The speed when printing in color is usually significantly lower than when printing with just black.

Matrix printer.

In dot matrix printers, the image is formed by a print head, which consists of a set of needles (a needle matrix) driven by electromagnets. The head moves line by line along the sheet, while the needles strike the paper through the ink ribbon, forming a dotted image.

The print quality of dot matrix printers is determined by the number of needles in the print head. Some models of 24-pin dot matrix printers are capable of color printing through the use of a multi-color ink ribbon, while the printer microprocessor generates signals to control the printer's print head needles in accordance with the color table. The quality of color printing achieved in this case is significantly inferior to the print quality of an inkjet printer, but is quite acceptable for printing business graphics(tables, charts, etc.).

One of the undoubted advantages of dot matrix printers is the ability to print several copies of a document simultaneously using carbon paper. The advantages of dot matrix printers are:

· low cost of consumables;

· durability of work;

· low cost of printing;

· relative cheapness of A3 dot matrix printers

Dot matrix printers provide printing speeds of up to 400 characters per second, have a resolution of 360 x 360 dpi, and are equipped RAM small volume - about 64 - 128 KB.

The main disadvantages of dot matrix printers are monochrome (although there were also color dot matrix printers, at a very high price), low operating speed and high noise level, which reaches 25 dB.

Jet printer.

The operating principle of inkjet printers is similar to dot matrix printers in that the image on the media is formed from dots. But instead of heads with needles, inkjet printers use a matrix of nozzles (the so-called head) that prints with liquid dyes. The print head may be built into the dye cartridges, or may be a part of the printer, and the replacement cartridges contain only the dye.

There are two ways to implement the dye spray method:

Piezoelectric - a piezoelectric crystal with a diaphragm is located above the nozzle. When an electric current is applied to the piezoelectric element, it bends and pulls the diaphragm along with it - a drop is formed, which is subsequently pushed onto the paper.

Thermal - a microscopic heating element is located in the nozzle, which, when passing electric current instantly heats up to a temperature of about 500 °C; when heated, gas bubbles form in the ink, which push drops of liquid from the nozzle onto the media.