System bus (bus)
It is the channel for connecting the microprocessor, the computer's RAM and peripherals. To exchange data with memory and with input/output devices, different bus components are used. Interaction of the microprocessor with the input-output devices is carried out through the data bus, and memory addressing occurs via the address bus.
The computer's random access memory (RAM) consists of random access memory (RAM) and read-only memory (ROM). To store the programs currently running and the data they use, RAM is used, which is available for reading and writing. When power is turned off, the contents of RAM are lost.
The amount of ROM memory is usually much smaller than RAM, the information in it is stored permanently, and its modification is either impossible at all, or it is possible only with the help of special devices (ROM programmers).
In order to correctly determine the amount of RAM required by a particular personal computer, it is necessary to start from the assumed functions of this workstation and the amount of information processed by it.
If this personal computer (PC) is part of a local network, where the bulk of the information needed for work is stored on the central computer, then the amount of information processed by it directly will be small. In this case, it is quite acceptable to use a PC with high speed, but a small amount of RAM.
If it is assumed that large volumes of information will be processed on this PC, large documents will be prepared, then you need to choose a computer with a large amount of memory.
Usually, information or commands are entered from the keyboard, and the results of the work are displayed. Therefore, the standard input device is the keyboard, and the standard output device is the video system, which consists of a display and video controller (video adapter, video card).
Displays are characterized by the size of the screen, the maximum resolution and other characteristics. The larger the screen size and resolution, the more information you can place on it and the more comfortable it is to work on it to a specialist.
There are also a number of additional devices that make it easier to work with a PC: a mouse, a light pen, etc. A great future for speech recognition and synthesis devices, as well as image recognition.
There are different types of storage media; let's take a look at the most common ones.
1. Hard drives on hard disks (hard disks, hard disk drives, HDD) and solid state drives (solid-state drive, SSD). As a rule, they are constantly located inside the PC system unit, however there are special removable hard disks. The capacity of hard drives of modern computers is on average 1-4 Tb.
2. Drives on laser disks (CD-ROM, DVD, Blu-ray Disk). They are able to store a large amount of information (from 600 MB to 50 GB) and provide high reliability. At the same time, the cost of laser disks is slightly higher than that of floppy disks. It should be noted that for most laser discs, only one-time recording of information is possible. However, there are also special recordable laser discs, the so-called CD-R or CD-RW (DVD-RW). If the first allow only a single entry of information, then for the second type it is possible to overwrite.
3. FLASH cards (including USB). Able to store a large amount of information (SD-cards - up to 128 GB, USB-flash drives - up to 256 GB) and provide a high level of usability, because they can store and repeatedly rewrite information.
Printers include printers and plotters. Types of printers differ in the ways of applying the dye (toner) to the paper. On this basis, printers are divided into matrix, inkjet and laser.
The most important characteristic of a printer is the quality of the output, i.e. resolution, which is measured by the number of dots per inch. The higher the resolution of the printer, the better the print quality.
Another important characteristic of the printer is the speed of printing. The highest quality and speed of printing is provided by laser printers.
Special devices that draw a pen are used to construct graphic images - plotters or plotters.
To this class of hardware are, first of all, various types of modems and cables. The main function of the modem is the conversion of digital information stored in the computer's memory into an analog signal for transmission over telephone lines and reverse conversion when receiving information. Modems are external and internal (in the form of a board built into the computer). A variation of the modem is a fax modem that can be used to send and receive facsimile messages in addition to functioning as a normal modem. Some modern models also have a built-in automatic number identifier.
Image input devices
Scanners are used to enter graphic images into PCs. The scanner creates an electronic copy of the image read from the paper in the computer. The image can be text, picture, photo, diagram or other graphic image.
The simplest scanners are handheld; When working with them, the user himself must move the scanner through the image. Such scanners are the cheapest, but with their help one can not enter the whole page image in one pass, since their standard width is 105 mm.
Much more convenient, but also more expensive tablet scanner. The sheet with the scanned image is placed in it entirely, and the process goes automatically.
As in all cases of working with images, an important parameter is the resolution of the scanner. The higher it is, the more accurately the resulting electronic image will match the original material.
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