Peripheral devices. Peripheral devices - a device structurally separated from the system unit. Devices that have their own control and work according to the commands of the system unit. Serve for external data processing. Peripheral devices include printers, scanners, modems, external storage devices.
Display facilities. Display means are, first of all, a monitor. All information about the operation of the computer is displayed on the monitor. The monitor allows you to track what is happening in the computer at a given time, what computing process the computer is busy with.
Motherboard. The motherboard is the main part of the system unit, to which all the devices of the system unit are connected. Through the motherboard, the devices of the system unit communicate with each other, exchange information, power supply. The faster the buses (communication channels of devices) of the motherboard, the faster the communication between the devices occurs, the faster the computer works.
HDD. Hard disk - serves for long-term storage of information, it contains programs necessary for the operation of the computer (Windows, Office, Internet Explorer.) and user files (Mail files, if used mail client, video, music, pictures.).
Video card. Video card - a board inside the system unit, designed to connect the system unit and the monitor, transfers the image to the monitor and takes on some of the calculations for preparing the image for the monitor. The image quality depends on the video card. The video card has its own built-in RAM and its own image processing processor. The higher the frequency of the video card processor and the more memory of the video card, the cooler (later released) games you can play on your computer.
CD / DVD-ROM. CD / DVD-ROM - a device for reading / writing CDs, CDs, DVDs. These devices differ in the speed of reading or writing information, as well as the ability to read / write various media. Nowadays it is difficult to find anything on sale other than omnivorous CD-ROMs. Modern CD-ROMs are capable of reading and writing both CDs and DVDs of various capacities.
Card reader A card reader is a device for reading / writing information on memory cards. Card readers differ in the speed characteristics of reading / writing information. Card readers are built-in system unit or constructively independent, connected to the system unit via a USB port.
Computer ports Computer ports are connectors on the system unit for connecting peripheral devices, manipulators and display devices. We will not talk about the connectors in detail, we will just list some of them: USB, VGA, Power connector, COM port, Ethernet port, Standard connector for audio output, etc.
Postscript I want to draw your attention to the fact that progress does not stand still and this article will become obsolete over time. But the architecture of the personal computer will not change so soon. Therefore, this text will be useful as an introductory part for studying computers in more detail. Every day new production technologies appear in the world or old methods are improved. Scientists and engineers are struggling with new inventions. But the "bicycle" has not yet been invented.
Units.
Many are interested in a computer, its programs and other computer accessories, but few have thought about the fact that all files in the form of pictures, videos, music are stored on a computer due to its memory. And it happens like this: The computer must have a storage device (HDD-disk, flash-disk, etc.) - this time. The memory on the computer is not infinite, so the file should not exceed the size of the free memory of the drive. In the recent past, PC memory was stored on disks that were able to memorize text smaller than that given, but at the same time they were the size of a room, and now a computer with a box is able to memorize hundreds of thousands of such texts, or even more.
Let's explain all this in the language of computer science:
Memory- in computer science - the ability of an object to provide data storage. The storage is carried out in storage devices.
Address- a number that identifies individual parts of memory (cells) and registers.
Associative memory- in computer science - unaddressed memory, in which information is searched for by its content (associative feature).
Bit- the minimum unit of measurement of the amount of transmitted or stored information, corresponding to one bit, capable of taking values 0 or 1.
Byte- in memory devices - the smallest addressable data unit in the computer memory processed as a whole. By default, a byte is considered to be 8 bits. Typically, in data coding systems, a byte is the code of a single printable or control character.
Byte- in the measurement of information - a unit for measuring the amount of information, memory capacity and storage capacity and the basis of derived units: -
1 byte = 8 bits,
1 kilobyte = 1024 bytes,
1 megabyte = 1024 KB,
1 gigabyte = 1024 MB,
1 terabyte = 1024 GB,
1 petabyte = 1024 TB.
On the Internet, there is also such a thing as connection speed. It is not measured in bytes, but in bits. Those. data loading occurs (under reference conditions) at a speed 8 times less than the speed of connection to the node. (since 1 byte has 8 bits)
Example: the real bandwidth of the communication channel is 1 Mbps, i.e. 1024Kbps Accordingly, the maximum data download speed through such a bandwidth = 1024/8 → 128Kbytes / sec. With this connection, a 10 MB file will download 10 / 0.128 = 80 seconds
How the PC works
Consider the principle of operation of a personal computer
The structure of a computer is somewhat reminiscent of the structure of a person. CPU, RAM and HDD perform brain functions; the motherboard and the chipset are the circulatory and nervous systems; a keyboard, mouse, microphone, scanner, and webcam (input devices) are similar to human vision, hearing, and other sensory functions; monitor and printer (output devices) are something like a language. From a technical point of view, the principle can be described in the following way:
A certain amount of information has appeared. The device that receives the information processes it and prepares it for dispatch using a common protocol. Such a device can be called a transmitter. Then, another device for transmitting data transmits the prepared information. The receiver or, as you already understood, the device receiving the information read the data using the same protocol and, based on some information that was laid down earlier, made a decision. As a response, this data was sent back using the same communication device. This is how, approximately, computer devices work with each other: they constantly process something and exchange data using common protocols that stipulate how to transmit and receive this data.
All information is stored on the hard drive. When you turn on the computer, some of the data required for normal functioning system is loaded into random access memory (RAM - random access memory). In addition, other devices can send their data there while the computer is running. The processor (CPU - central processing unit) is responsible for data processing. Information enters the CPU from RAM, and after processing it is returned to the same place. And then it can be sent to the addressee, that is, to the device that sent this data to the RAM for further processing (though this does not always happen, but more on that later). If you need to save information for a long time, then you "dump" it to the hard disk, since RAM can store data only if it is constantly powered. If some device suddenly wants the CPU to process something for it, then first you need to prepare the data, then, by sending it to memory, tell the processor that this data needs to be processed. Wait, and then maybe (depending on the task at hand) receive the processed data back, or maybe to some other device to send it. There are many devices, but the processor is one and all of them are not enough at once. What to do? It's very easy to get in line and wait. There is a hierarchy among devices. For some, the CPU will process the data immediately, while others will have to wait until the second coming.
It is clear that the user must observe a certain result of his work. This is what the monitor is intended for, the data for which is prepared by the video card (by the way, it is this device that can access the CPU bypassing the RAM).
For example: You started MS Word and pressed some key, say [G]. On the screen, a letter appeared in the text field, and what is important, it is the letter G. What happened? Firstly, by launching the MS Word program, you gave it control of the computer (which is also under the control of the operating system). Secondly, by pressing the [G] key, we made the keyboard mini-processor send the code for this key to the computer. Thirdly, the processor, having processed the command and data that were prepared by the program, sent them to the video card. Fourthly, the video card, having received the command and data and processed them in its own way, sent everything to the monitor, and that, in turn, displayed what was ordered. Everything. On the screen you see the letter G. From the last example, we can conclude that a computer is not only its hardware, but also software. That is, one cannot be separated from the other. Moreover, I will tell you - any computer device has its own control program, which is called a driver. Without such programs, most of the computer's devices will not work. General management the operating system (OS) takes over the computer. By the way, this is the most weakness modern PC. In general, it should be noted that all PCs operate according to the von Neumann principles of program control. Hungarian by nationality John von Neumann emigrated to the United States in 1930, where in 1945 he developed the principles of computer program control. And until now, the world of information technology uses these rules (although they are not the most convenient and have their own shortcomings), since no one can really offer anything else (there are also non-Von Name computers, but they still have even greater drawbacks). These are the rules:
1. The principle of binary coding. This means that all information in the computer is transmitted and stored in binary form.
2. The principle of programmed control. Here we are talking about the fact that the program is a set of commands that the processor executes automatically and in a certain sequence.
3. The principle of homogeneity of memory. Information of different types differs in the way it is used, not in the way it is encoded.
4. The principle of targeting. The information is located in memory cells that have an exact address. Knowing the address, the CPU can access the information it needs at any time.
PC device
Let's divide the parts of the computer into four main groups:
· System unit:
The system unit, the main part of the computer, where all computing processes take place. The system unit is quite complex and consists of various components. We'll look at these components later.
· Peripherals:
Peripheral devices - a device structurally separated from the system unit. Devices that have their own control and work according to the commands of the system unit. Serve for external data processing. Peripheral devices include printers, scanners, modems, external storage devices.
· Manipulation means:
Manipulation tools: keyboard, mouse, game joystick. All those devices with the help of which we "tell" the computer what to do, what computing processes to start at the moment.
· Display means:
Display means are, first of all, a monitor. All information about the operation of the computer is displayed on the monitor. The monitor allows you to track what is happening in the computer at a given time, what computing process the computer is busy with.
System unit device:
· Motherboard- the main part of the system unit, to which all the devices of the system unit are connected. Through the motherboard, the devices of the system unit communicate with each other, exchange information, power supply. The faster the buses (communication channels of devices) of the motherboard, the faster the communication between the devices occurs, the faster the computer works. 
· CPU- the brain of the system unit, performs logical operations. The speed of the computer and its entire architecture largely depend on its speed, frequency. 
· RAM- memory for temporary storage of data in a computer, used only when the computer is running. The speed of the computer depends on the amount and speed of RAM. 
· HDD- serves for long-term storage of information, it contains programs necessary for the computer (Windows, Office, Internet Explorer.) And user files (Mail files, if you use an email client, video, music, pictures). 
· Video card- the board inside the system unit, designed to connect the system unit and the monitor, transfers the image to the monitor and takes part of the calculations on preparing the image for the monitor. The image quality depends on the video card. The video card has its own built-in RAM and its own image processing processor. The higher the frequency of the video card processor and the more memory of the video card, the cooler (later released) games you can play on your computer. 
· Sound card- designed to prepare sound signals played by the speakers. A sound card is usually built into the motherboard, but it can be structurally separated and connected via a bus. 
· Network Card- a board, a device, is installed in the motherboard or built into it. A network card is used to connect a computer with other computers over a local network or to connect to the Internet. 
· CD / DVD-ROM- a device for reading / writing CDs, CDs, DVDs. These devices differ in the speed of reading or writing information, as well as the ability to read / write various media. Nowadays it is difficult to find anything on sale other than omnivorous CD-ROMs. Modern CD-ROMs are capable of reading and writing both CDs and DVDs of various capacities. 
· Drive- a device designed to read / write information to floppy disks. V modern computers rarely installed. A card reader is installed in place of disk drives in modern computers. 
· Card reader- a device for reading / writing information on memory cards. Card readers differ in the speed characteristics of reading / writing information. Card readers are built into the system unit or constructively independent, connected to the system unit via a USB port. 
· Computer ports- connectors on the system unit for connecting peripheral devices, manipulators and display devices. We will not talk about the connectors in detail, we will just list some of them: USB, VGA, Power connector, COM port, Ethernet port, Standard connector for audio output, etc. 
· Power Supply- a unit that powers all devices inside the computer. Power supplies differ in power. The more powerful the power supply, the more load it can "hold" 
· Coolers- fans designed for air cooling... Usually coolers are installed inside the power supply, on the processor, on the video card. An additional cooler can be installed on the system unit to cool the entire unit.
· Radiators- metal plates are installed to remove heat from the processors in the system unit. Usually radiators are cooled by coolers, but not always.
The main peripherals PC:
The main peripheral devices of a computer include a printer and a scanner. The printer is designed to output information from a computer onto paper. Printers can be divided into laser and inkjet printers.
· Inkjet printers print on paper using ink taken from cartridges. Printers can be equipped with a different number of cartridges, it all depends on the model. Inkjet printers are usually color. There are inkjet printers that can print photos. Some photo printers can be connected to the camera / phone directly, bypassing the computer. The disadvantage of inkjet printers is that they are expensive to print; ink from paper is usually washed off with water. 
· Laser printers come in color and black and white. Laser printers print using a laser beam. The laser beam bakes toner onto the paper, which is released from the cartridge onto the paper. Laser printers differ in print speed, the number of sheets printed per minute. Usually, laser printers stand in offices, because have a high print speed and an inexpensive printed sheet. Like inkjet printers, laser printers have cartridges. These cartridges are filled with toner (powder). 
· Scanner- a device for scanning documents, photos and even photo negatives. The most common type of scanners is flatbed. Different scanners have different scanning speeds. Also, scanners can be divided by the extension that they support when scanning. Some scanners have a special device for scanning negatives. The scanner is usually connected to a computer via a USB port. 
· Multifunctional devices- printer / scanner / copier (copier) in one device. Combine all of the above functions. A distinctive feature of such devices is the ability to use them as a copier, bypassing a computer. Such combined devices can be both inkjet and laser. 
· Graphics tablet- a device for manual input of graphic information, images by moving a special pointer (pen) on the tablet; when you move the pen, the coordinates of its location are read automatically and these coordinates are entered into the PC 
Manipulation means:
· Keyboard and Mouse- these are the main means of manipulation, computer control. Also, various joysticks, steering wheels with pedals, steering wheels can be attributed to the means of manipulation, but they are mainly designed to control the game process. It should be noted here that not all released games can correctly use or even use this or that game pad. 
DDR SDRAM
Compared with ordinary memory SDRAM type, with double the data rate, the throughput was doubled. (Initially, this type of memory was used in video cards, but later there was support for DDR SDRAM on the part of chipsets.)
For reference: DDR SDRAM operates at frequencies of 100, 133, 166 and 200 MHz, its time full access- 30 and 22.5 ns, and the duty cycle is 5, 3.75, 3 and 2.5 ns. Examples of designation of memory modules: DDR200, DDR266, DDR333, DDR400
DDR2 SDRAM
A structurally new type of DDR2 SDRAM was released in 2004. Based on DDR SDRAM technology, due to technical changes, this type of memory shows a higher performance and is intended for use on modern computers.
For reference: the memory can operate at bus clock speeds of 200, 266, 333, 337, 400, 533, 575 and 600 MHz. In this case, the effective data transmission frequency will be respectively 400, 533, 667, 675, 800, 1066, 1150 and 1200 MHz. Some manufacturers of memory modules, in addition to standard frequencies, also produce samples that operate at non-standard (intermediate) frequencies. They are intended for use in overclocked systems where frequency headroom is required. Full access time - 25, 11.25, 9, 7.5 ns or less. The duty cycle is 5 to 1.67 ns.
DDR3 SDRAM
This type of memory is based on DDR2 SDRAM technologies with twice the data transfer rate on the memory bus. Differs in lower power consumption compared to its predecessors. The bandwidth frequency ranges from 800 to 2400 MHz (the record is over 3000 MHz), which provides more bandwidth than all its predecessors.
DRAM memory designs
DRAM memory is constructively performed as separate microcircuits in DIP, SOIC, BGA cases and in the form of SIPP SIMM, DIMM, RIMM memory modules (for PCI slots of system units)
The bottom picture of the case shows: from top to bottom: DIP, SIPP, SIMM (30-pin), SIMM (72-pin), DIMM (168-pin), DIMM (184-pin, DDR)
For example, the following are enclosed versions of RAM cards used in modern laptops: 
HDD.
Hard disk drive or HDD(English hard (magnetic) disk drive, HDD, HMDD), hard disk, in computer slang "winchester", "screw", "hard", "harddisk" - a storage device based on the principle of magnetic recording. It is the main data storage device in most computers.
Unlike a "floppy" disk (floppy disk), information in a hard disk drive is recorded on hard (aluminum or glass) plates covered with a layer of ferromagnetic material, most often chromium dioxide. The HDD uses one or more plates on one axis. The readheads in the operating mode do not touch the surface of the plates due to the interlayer of the incoming air flow formed at the surface during rapid rotation. The distance between the head and the disc is several nanometers (in modern discs about 10 nm), and the absence of mechanical contact ensures a long service life of the device. In the absence of rotation of the disks, the heads are located at the spindle or outside the disk in a safe zone, where their abnormal contact with the surface of the disks is excluded.
Also, unlike a floppy disk, a storage medium is combined with a drive, a drive and an electronics unit and (in personal computers in the overwhelming majority of cases) is usually installed inside the computer's system unit.
Main characteristics
Interface(English interface) - a set of communication lines, signals sent along these lines, technical means supporting these lines, and the rules (protocol) of the exchange. Commercially available internal hard drives can use ATA (aka IDE and PATA), SATA, eSATA, SCSI, SAS, FireWire, SDIO, and Fiber Channel interfaces.
Capacity(eng. capacity) - the amount of data that can be stored by the drive. Since the inception of the first hard drives, as a result of the continuous improvement of data recording technology, their maximum possible capacity has been continuously increasing.
Physical size(form factor) (eng. dimension). Almost all modern drives for personal computers and servers are either 3.5 or 2.5 inches wide - the size of standard mounts for them, respectively, in desktops and laptops. Also widespread are the formats 1.8 ", 1.3", 1 "and 0.85". The production of drives in the form factors of 8 and 5.25 inches has been discontinued.
External HDD storage
External HDD storage is regular hard a disk placed in a case and having a USB or FireWire output for connecting to a computer or other device with which you want to exchange data. External USB hard drives became popular in the 2000s, thanks to the general "mobilization". Portable hard drives differ, first of all, in the volume and speed of work.
Practically, external USB HDDs have exactly the same volumes as regular ones, so now you can buy external HDD up to 1 TB. Currently, external hard drives are produced by more than 30 companies around the world.
Network adapters.
Wired network controllers
Network board also known as network card, network adapter, ethernet adapter, NIC (English network interface card) - a peripheral device that allows the computer to communicate with other devices on the network. Nowadays, especially in personal computers, network cards are quite often integrated into motherboards for convenience and reduce the cost of the entire computer as a whole.
Types of network cards:
internal- separate cards inserted into the ISA, PCI or PCI-E slot;
external connected via USB or PCMCIA interface, previously mainly used in laptops;
embedded into the motherboard.
On 10-megabit network cards for connection to a local network use 4 types of connectors:
· 8P8C for twisted pair;
· BNC connector for thin coaxial cable;
· 15-pin AUI transceiver connector for thick coaxial cable.
Optical connector (en: 10BASE-EL and other 10 Mbps Ethernet standards)
These connectors can be present in different combinations, sometimes even all three at once, but at any given moment only one of them works.
On 100-megabit boards install either a twisted pair connector (8P8C, aka RJ-45) or an optical connector (SC, ST, MIC). Next to the twisted pair connector, one or more information LEDs are installed that indicate the presence of a connection and information transfer. Since our networks within the entrance are built using Fast Ethernet technology - network card must support 8P8C connector.
It is customary to share several generations of network controllers. Today's network adapters are of the fourth generation. These adapters necessarily include an ASIC that performs the functions of the MAC-level (MAC-PHY), the speed is developed up to 1 Gbit / s, and there are also a large number of high-level functions. The set of such functions may include support for the RMON remote monitoring agent, frame prioritization scheme, functions for remote computer control, etc. Server versions of adapters almost necessarily have a powerful processor that offloads the central processor.
Wireless network controllers
WI-FI is a technology that allows you to create computer networks that fully comply with the standards for conventional wired networks (for example, Ethernet), without the use of cabling. The transmission medium in such networks is radio waves 2.4 and 5 GHz
Wireless network controller... As you can imagine, this is the adapter that connects your computer to wireless network.
Wi-Fi controllers are of several types:
· Built-in. Already built into the motherboard. Most often used in laptops or PDAs. As a rule, you cannot dismantle the built-in controller from the computer, but you can disable it and use another one instead. Most modern laptops have built-in Wi-Fi controllers. It is worth highlighting the mass-produced controllers built on chips: Atheros, Broadcom, VIA, Realtek.
Internal with PCI interface. Perhaps one of the most common types of network controllers for personal computers. Typically, these NICs have one LED, an activity indicator, and an antenna slot. The boards can be supplied with different types of antennas: pin, which is installed directly on the adapter bracket and remote.
Internal with PCMCIA interface. The most convenient way to add wireless networking support to a laptop that is not equipped with wireless networking by default. They have a built-in antenna, are compact and easy to set up. There are also adapters with foldable large antennas that provide an increased range of the wireless network.
External USB controllers with USB interface. This is the most versatile type of controller and the most convenient. You can use the USB controller with both a laptop and a personal computer. This type of controller is especially relevant for owners of SFF computers, such as Shuttle XPC. Such controllers are convenient to carry with you and you can take them on a trip or vice versa - keep them at home or in the office as spare, in case guests come to you with laptops without Wi-Fi controllers, but who desperately need the Internet on their machines.
The basics information networks
Computer network concept
Let's start by defining a computer network.
Computer network - two or more computers connected by a transmission medium (for example, a network cable). The main function of the network is to enable the exchange of information between network users.
The same concept fits the principle of resource sharing, when a network user can access information, a program or a device located on another computer. For example, network users can work with network programs and files on a remote computer, or print to a printer that is physically connected to any computer on the network. To implement network access to resources, programs, files or printers must be shared.
Evolution of networks
The first multi-terminal systems appeared in the early 60s as a way of organizing the computing work of users. The principle of operation of multi-terminal systems is to divide the computing resources of one powerful computer between a number of users. Terminals carry out only output of information to the display and provide input from the keyboard. The entire computational load is taken over by a large and powerful computer. In the 1960s, these computers were the IBM mainframes - powerful and reliable general purpose computers.
WAN (wide area networks)
The first global networks ( Wide area Network - WAN) appeared as a result of solving the problem of terminal access to a central computer, remote from it at a great distance, of the order of hundreds of kilometers. And in order to interconnect central computers with each other, the type of communication "computer-computer" was developed. Now it is possible to access the resources of several large computers of the supercomputer class from the terminal. Some networking services have been implemented using the computer-to-computer communication type, such as file sharing, email, and others.
LAN (local area networks)
The first Local Area Networks (LANs) appeared in the early 70s as a result of a technological breakthrough in the field of electronics - large integrated circuits appeared. For changing large computers mini-computers came, which were much cheaper, and in performance they were not inferior to mainframes. Thus, each department of the enterprise was able to install its own multi-terminal system. And in order to connect the systems of departments into a single network of the enterprise, various non-standard interface devices were used.
Standard local area networks
The next step in the evolution of computer networks is the appearance of the first personal computers (PCs). It was the appearance of the PC that gave impetus to the standardization of local area network technologies. In the mid-80s, standards such as Ethernet, Arcnet, Token Ring appeared. The standards make the process of deploying local area networks easier. To deploy a network, it is enough to install standard network adapters, for example, Ethernet, connect them with a standard cable using standard connectors, and install an operating system (OS) on the computer that supports standard network protocols.
Classification of networks
LANs (Local Area Networks) are networks that connect computers within one or more adjacent buildings.
A distinctive feature of local networks is the use of high-speed highly reliable transmission media, such as coaxial cable or twisted pair. Distances covered by local area networks usually do not exceed several kilometers.
WANs (Wide Area Networks) are networks that interconnect computers or local area networks that are far apart from each other. Global networks can connect different cities, countries, and even continents. An example of a global network is worldwide network Internet. A distinctive feature of global networks is the use of a wide variety of data transmission technologies, including over low-quality lines. This is the reason for the use of highly reliable protocols in global networks that can guarantee the delivery of data without loss and distortion. In addition, the data transfer rates on wide area networks are generally much lower than on local area networks.
MAN (Metropolitan Area Networks). This class it is not always customary to distinguish it as a separate one when classifying networks. It refers to networks that cover distances of up to hundreds of kilometers. As a rule, they unite local networks of a single administrative subordination. Usually, the transport basis of such networks is formed by high-speed networks using optical fiber as a transmission medium.
Logical topology of ER-Telecom network
The structure of the ER-Telecom cable network assumes four levels. The first three are optical: main (city level), sub-main (campus level) and house inputs (mini-campus level). The fourth level is electrical (house distribution networks). The backbone level connects the central head station with the head stations. Currently, the backbone layer has a star topology. The sub-trunk level connects the Head Stations (PBC) with the mini-campus nodes. All in-campus wiring is done with a four-core optical cable. Two cores are used for the needs of cable television, two for the needs of the Internet. An optical coupler is installed on every house, which produces fission optical signal as a percentage. The sub-line topology is an optical ring. Each mini-campus node serves 24 houses, included in optics. This scheme allows you to cover the maximum number of houses. The ring connection topology used by ER-Telecom allows, firstly, to increase the economic efficiency of network construction. Loop connection saves cable. Secondly, the use of coaxial cable is minimized for external routing between houses. The ring circuit for switching on the mini-campus nodes provides for optical redundancy for supplying a television signal. Thus, when the optical ring is broken, the switching of the optical signal in the opposite direction is provided. This significantly increases the reliability of the network.
TIRE
In bus topology networks, computers are connected to a single cable. Information can be spread over the cable in both directions. The advantages of networks with the "Bus" topology are the low cost and simplicity of cabling. The cable is connected to the computer's network board using a special T-shaped connector.
Disadvantages - low reliability (for any defect in the cable system, the entire network fails) and low performance, because only one computer can transmit at a time.
STAR
In networks with a "Star" topology, computers are connected to a central hub (hub), which serves to transfer information from one of its ports to all the others. Advantages - higher fault tolerance, since only a failure of the hub can lead to a network shutdown. In addition, some models of hubs can act as smart filters that control the flow of information or block transmissions prohibited by the administrator. Disadvantages - additional costs for equipment and network installation.
RING
In a ring network, the computers are connected in series to close the ring. Information circulates around the ring in one direction. Ring topology networks provide a convenient opportunity for the sender to control the correctness of message reception, because the data, having made a turnover, will return to the sender. The disadvantages of such networks include the complexity of the algorithms for monitoring and restoring the integrity of the ring.
Devices designed to interact with objects of windows of folders and programs on the monitor screen in the same way as a hand would do, refer to manipulators (from lat. manipula - hand). Relative manipulators: mouse, joystick, touch pad; absolute - digitizer.
Mouse - a device for positioning the mouse pointer (in the form of an arrow, a cross, a vertical stick) on the screen image and for interacting with objects by giving commands to the buttons. The use of the mouse is based on the capabilities of the graphical interface (user-computer interaction) provided by modern operating systems.
An ordinary mouse slides on the table or on the mat, but when moving it, the sensors transmit data about the direction and length of the path to the system unit through the mouse tail-cable.
Mouse clicks send additional command codes. The processor processes all incoming codes and sends control signals to change the position of the mouse pointer on the screen image or a command.
The mouse has a primary and secondary buttons that can be pressed (hold down), clicked (to
short press) to start a program or open a file.
Mouse actions have several options:
- click buttons - pressing the right or left button with a quick release;
- double click- double short and quick pressing of the button;
- button hold when moving the mouse, allows you to select, hook and move an object or border;
- key hold keyboards Ctrl, Shift or Alt when the mouse button is pressed, modifies its action and the commands given.
By itself, moving the mouse without pressing any buttons causes the mouse pointer to slide across the screen over objects, but does not issue commands. Nothing happens except pop-up tips appear. But when the pointer is positioned and the mouse button is clicked, the image object will be affected.
Position of fingers on mouse buttons: index finger - left button; ring finger - right button; middle finger - scroll wheel (if available) or middle button (for a 3-button mouse); for a 2-button mouse, the middle finger is not used.
The main mouse button (usually the left one) is briefly pressed with the index finger (click) to select the position of the cursor in the text, select or make an object active on the screen.
Attention! Double-clicking opens a folder or file, if the clicks are short, sketchy, with very close spacing. Do not crush the mouse button, do not get stuck when pressed. You cannot push, jerk the mouse at the moment of clicking on the folder, because, having hooked the folder, the mouse may not open it, but push it into the next folder. Two gentle, but short presses (click-click) are required.
A long press of the mouse button while moving it is used to select an area of text or a picture, drag and drop with a "hook", displacement of objects and their borders on the screen. Some actions are performed by the mouse in combination with pressing the keys on the keyboard. For example, Ctrl and the left mouse button with the object's hook - not moving, but copying.
The operating system instructs the auxiliary mouse button (usually the right one) to open the context menu of commands or parameters (a list for selecting commands according to the position of the pointer on the screen). Contextual commands depend on the program in which you are currently working with the mouse.
In some models of mice, some additional service command is performed by the middle button (for example, closes Windows windows) or the scroll wheel of the contents when viewed in the windows of folders and programs.
The mouse is operated by a special program - the mouse driver. In the operating system Windows setting mouse executes the command Start, Control Panel, Mouse. You can change the maximum speed (frequency) of pressing the mouse button (interval of clicks), change the appearance of the pointer and its sensitivity to mouse movement, change the assignment of the primary and secondary buttons for left-handers.
A mechanical mouse follows its movement by rotating an inner ball that rolls on the mat. The optical mouse scans the flashing points of the surface with photocells and can work without a rug. The radio mouse and gyroscopic mouse take into account and transmit their movement using a radio signal, without a mat and without a cable. Such bats are suitable for remote control, in particular for presentations. (A gyroscope is a spinning top spinning up to a high speed, the axis of rotation of which has the property of holding its position under external influences. Gyroscopes are used to orientate flying objects, and now also "bats".) An interactive mouse has a vibration generator inside for transmitting tactile sensations, accompanies movement "by touch", with elasticity and trembling, transmits the passage of the pointer over the program buttons and across the window border.
Digitizer- a device for inputting a graphic vector image obtained as a result of movement of the pointer over a special surface by the hand of a PC operator. The device consists of graphics tablet and pointer (pen, cursor). The tablet connects to the PC and the pen connects to the tablet. The principle of operation of the digitizer is based on fixing the location of the pointer using a grid of conductors built into the tablet. The step of reading information is called the resolution of the digitizer. Digitizers are used when working with computer-aided design systems and graphic editors.
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Introduction
At all times, people had to count. In the hazy prehistoric past, they counted on fingers or made incisions on bones. Approximately about 4000 years ago, at the dawn of human civilization, quite complex number systems were invented, which made it possible to carry out trade transactions, calculate astronomical cycles, and carry out other calculations. Several millennia later, the first hand-held computing instruments appeared. And nowadays, the most complex computational problems, like many other operations seemingly unrelated to numbers, are solved with the help of an "electronic brain" called a computer.
Experts will probably not fail to note that a computer is not a brain (at least not yet, some will clarify). It is simply another tool, another device designed to make our work easier.
Data I / O design is a practical area closely related to computational theory and engineering. Its historical roots go even deeper than computers, and the best minds of the computer era were engaged in its development. Scientists and engineers have found effective solutions to two main issues - how to enter data and instructions into a computer and how to extract processed information from it in the most convenient form - have been embodied in the creation of a variety of hardware and software tools. These inventions expanded the scope of computers to almost the limits of the human imagination - from the detailed design of artificial bones to the execution of musical works or control of an "unguided" aircraft.
1. Computer device
Let's divide the parts of the computer into four main groups:
1. System unit;
2. Peripheral devices.
3. Means of manipulation;
4. Display facilities;
The system unit, the main part of the computer, where all computing processes take place. The system unit is quite complex and consists of various components. We'll look at these components later.
Manipulation tools: keyboard, mouse, game joystick. All those devices with the help of which we "tell" the computer what to do, what computing processes to start at the moment.
Display means are, first of all, a monitor. All information about the operation of the computer is displayed on the monitor. The monitor allows you to track what is happening in the computer at a given time, what computing process the computer is busy with.
Peripheral devices - a device structurally separated from the system unit. Devices that have their own control and work according to the commands of the system unit. Serve for external data processing. Peripheral devices include printers, scanners, modems, external storage devices.
System unit device:
The motherboard is the main part of the system unit, to which all the devices of the system unit are connected. Through the motherboard, the devices of the system unit communicate with each other, exchange information, power supply. The faster the buses (communication channels of devices) of the motherboard, the faster the communication between the devices occurs, the faster the computer works.
The processor is the brain of the system unit, it performs logical operations. The speed of the computer and its entire architecture largely depend on its speed, frequency.
Random access memory - memory for temporary storage of data in a computer, used only when the computer is running. The speed of the computer depends on the amount and speed of RAM.
Hard disk - serves for long-term storage of information, it contains programs necessary for the computer (Windows, Office, Internet Explorer.) And user files (Mail files, if you use an email client, video, music, pictures.).
Video card - a board inside the system unit, designed to connect the system unit and the monitor, transfers the image to the monitor and takes on some of the calculations for preparing the image for the monitor. The image quality depends on the video card. The video card has its own built-in RAM and its own image processing processor. The higher the frequency of the video card processor and the more memory of the video card, the cooler (later released) games you can play on your computer.
Sound card - designed to prepare sound signals reproduced by speakers. A sound card is usually built into the motherboard, but it can be structurally separated and connected via a bus.
Network card - a board, device, installed in the motherboard or built into it. A network card is used to connect a computer with other computers over a local network or to connect to the Internet.
CD / DVD-ROM - a device for reading / writing CDs, CDs, DVDs. These devices differ in the speed of reading or writing information, as well as the ability to read / write various media. Nowadays it is difficult to find anything on sale other than omnivorous CD-ROMs. Modern CD-ROMs are capable of reading and writing both CDs and DVDs of various capacities.
A floppy drive is a device designed to read / write information to floppy disks. It is rarely installed in modern computers. A card reader is installed in place of disk drives in modern computers.
Card reader - a device for reading / writing information on memory cards. Card readers differ in the speed characteristics of reading / writing information. Card readers are built into the system unit or constructively independent, connected to the system unit via a USB port.
Computer ports - connectors on the system unit for connecting peripheral devices, manipulators and display devices. We will not talk about the connectors in detail, we will just list some of them: USB, VGA, Power connector, COM port, Ethernet port, Standard connector for audio output, etc.
Power supply unit - the unit that powers all the devices inside the computer. Power supplies differ in power. The more powerful the power supply, the more devices you can connect to the inside of the system unit.
Coolers are fans designed for air cooling. Usually coolers are installed inside the power supply, on the processor, on the video card. An additional cooler can be installed on the system unit to cool the entire unit.
Radiators - metal plates are installed to remove heat from the processors in the system unit. Usually radiators are cooled by coolers, but not always.
Main PC peripherals:
The main peripheral devices of a computer include a printer and a scanner. The printer is designed to output information from a computer onto paper. Printers can be divided into laser and inkjet printers.
Inkjet printers print on paper using ink taken from cartridges. Printers can be equipped with a different number of cartridges, it all depends on the model. Inkjet printers are usually color. There are inkjet printers that can print photos. Some photo printers can be connected directly to the camera / phone, bypassing the computer. The disadvantage of inkjet printers is that they are expensive to print; ink from paper is usually washed off with water.
Laser printers are available in color and black and white. Laser printers print using a laser beam. The laser beam bakes toner onto the paper, which is released from the cartridge onto the paper. Laser printers differ in print speed, the number of sheets printed per minute. As a rule, laser printers are located in offices, because have a high print speed and an inexpensive printed sheet. Like inkjet printers, laser printers have cartridges. These cartridges are filled with toner (powder).
Scanner- a device for scanning documents, photos and even photo negatives. The most common type of scanners is flatbed. Different scanners have different scanning speeds. Also, scanners can be divided by the extension that they support when scanning. Some scanners have a special device for scanning negatives. The scanner is usually connected to a computer via a USB port.
Multifunctional devices - printer / scanner / copier (copier) in one device. Combine all of the above functions. A distinctive feature of such devices is the ability to use them as a copier, bypassing a computer. Such combined devices can be both inkjet and laser.
Manipulation means:
Keyboard and mouse, these are the main means of manipulating, controlling a computer. Also, various joysticks, steering wheels with pedals, steering wheels can be attributed to the means of manipulation, but they are mainly designed to control the game process. It should be noted here that not all released games can correctly use or even use this or that game pad.
P.S:
I want to draw your attention to the fact that progress does not stand still and this article will become outdated over time. But the architecture of the personal computer will not change so soon. Therefore, this text will be useful as an introductory part for studying computers in more detail.
Every day new production technologies appear in the world or old methods are improved. Scientists and engineers are struggling with new inventions. But the "bicycle" has not yet been invented.
Some very zealous opponents of the Stone Age predict the imminent extinction of keyboards. They motivate this by the fact that the keyboard will replace speech input. Of course, it would be very good, but there are, firstly, different languages (it is not proper, for example, for Russian to speak English), and, secondly, not everyone can do without interjections like "mmm ...", "uh ...", "This ... how is it there? ..." and so on. All this creates problems in writing. software, which, in principle, can be written, but difficult, and it requires a lot of resources. At this stage in the development of personal computers, even the most primitive speech recognition system, the reliability of which would be sufficient to replace the keyboard, is very demanding on system resources. Therefore, it is unlikely that in the foreseeable future it will go into the "stone age" (or, more precisely, we will leave it), so the keyboard will remain the standard for a long time and, perhaps, the only means of entering text information. By the way, how, when the operating system is not yet loaded, enter the BIOS or install this very system? Embed support for speech input in the BIOS? Well, before that, oh, how far away.
Based on the foregoing, some attention should be paid to the choice of keyboard. When you go to the store for this very "non-evolving" device, pay attention to the following factors:
Ergonomics
Keyboard type
Ease of keystroke
Interface
Additional features
Let's start in order. It's not for nothing that I put the ergonomics of the keyboard in the first place, since, in my opinion, this is the main thing - if the keyboard is not comfortable, then a fast processor and a powerful video card will hardly be able to correct the situation, and it is better not to save money on the keyboard. After all, you may have to type on it more than a dozen megabytes of text, and if you worked a lot with text on a bad keyboard, you should know that the latter very darkens the whole picture. And many users, unfortunately, pay very little attention to this and are guided by the principle "the cheaper the better." And in vain. Although, on the other hand, when playing in Unreal, the quality of the keys is not particularly important, but it is still more pleasant to press good keys, and it’s not all the time to play in Unreal! So spare a few extra dollars (although I, however, have hardly met people who have "extra" dollars) and buy a good keyboard.
Ergonomics
Ergonomics can be understood as all the properties of a keyboard that are related to usability. We will discuss only the most, in my opinion, the most important of them.
The location of the keys, as well as their shape, size, and so on. There are several keys that can have different shapes and sizes: BackSpase, Enter, Shift.
There are two types of BackSpase keys: large or small. It is preferable, of course, a large one, because it is easier to hit on it, but the payment for this is the downward shift of the slash key and, as a consequence, the small Enter key.
Which also happens to be large. But the small size is quite enough, so it seems to me that it is better, considering the fact that BackSpase is getting large. True, there are keyboards that have large BackSpace and Enter, but then the right Shift is shortened, which is very bad. If the Enter key is large, then there are also two options: in the form of the letter "L" turned in the other direction, and in the form of the letter "G". The last option is the most inconvenient, since pressing usually occurs on the near part of the key, and in the L-configuration it is easy to touch the adjacent keys.
As already mentioned, depending on the sizes of Enter and Backspace Shift key(right) may decrease. This is highly undesirable, because Shift is used often, especially in combination with other keys, and it is quite easy not to get on it in this case. For example, it is easy to use the Cntrl + Shift combination to switch the keyboard layout, but when this Shift is small, it becomes not so convenient. True, you can use the left Shift "th, but after all, two hands must be used when typing.
Therefore, choose a keyboard with a large Shift and BackSpace and a small Enter. A good alternative is also this key configuration: a small BackSpace, a large L-shaped Enter and a large Shift key. But the first option seems to me to be better.
There are keyboards with the so-called Eraze-Eaze configuration, in which the space bar is divided into two halves. One of them (optional) acts as a space bar, and the other acts as the BackSpace keys. This was done again for convenience, but the doubtfulness of the idea lies in contradiction to the basic rule of blind dialing, according to which the space is pressed by the free (and therefore any) hand. That is, if the last letter of a word is entered by one hand, then the subsequent space is entered by the other. Fortunately, in the case of Eraze-Eaze, you do not have to program the halves, leaving both the Space function (space). Some keyboards may have an increased Escape. This feature can be attributed to the pluses, because it becomes easier to get to it. True, this is already easy to do, because Escape is always located separately.
In connection with the emergence of operating systems that allow you to manage power supply, modern keyboards usually (although not necessarily always) have three so-called sleep keys that allow you to sleep, wake up and turn on / off the computer. Whether these keys are needed is up to you, but if they are, then pay attention to their location. There are three options: the keys are located next to the paging keys in the bottom row, the keys are located next to the paging keys in the top row, the sleep keys are located above the Break group, while the Break group is pushed down and merged with the paging keys. The last option is bad in that if you are used to pressing Insert (for example, Shift + Insert), then due to the change in the usual arrangement of the keys, you can press PrintScreen, and a picture of a megabyte by 3-4 or more will be pushed into the buffer (depending on resolution and color palette), and even overwrite the previous content. The second way of positioning is even "better" - when you click on the intended Insert, you will actually be pressing the power off key. Therefore, the first option, in my opinion, is the best.
For those using the great and mighty Russian language, it is important how the Russian keyboard layout is made and what color the Russian letters are applied in. The Cyrillic layout can be Russian (Russian and Russian Typewriter. The typewriter layout, as the name suggests, repeats the keys of a typewriter. It was almost standard before Windows, in which a new layout appeared. They are almost the same, but in Russian they were introduced small but effective improvements. For example, the almost unused letter "ё" was moved to a far corner, and in its place was replaced by a key with frequently used periods and commas. that a foreign company has developed a more perfect layout for us.
The layout of the Cyrillic alphabet, of course, depends only on the driver (Windows usually has Russian after installation, but you can also change it), and you can buy stickers or just remember the location of inappropriate labels. But is it worth doing this? Therefore, choose a keyboard with a Russian layout. By the way, others are no longer produced. The color of the applied Cyrillic alphabet is also of great importance. Better, of course, red, since the red color is immediately noticeable, but in principle, this is a matter of habit. Although preference should probably still be given to red.
Microsoft at one time spent almost two years developing a new type of keyboard designed for Windows 95. This keyboard was named Natural Keyboard. Literally translated - a natural keyboard, in the literary - ergonomic. Subsequently, this name became a household name. The Natural Keyboard has vertical rows of keys that are rotated to the sides, corresponding to the zone of each hand. The user is relieved of the stress of keeping the hands parallel to each other. The profile of the alphabetical part of the keyboard presents a convex arc. This eliminates the need to keep the hands parallel to the plane of the table. There is a hand rest. After looking at the Natural Keyboard, it's clear that legacy keyboards simply inherited the conservative style of typewriters. Natural Keyboard has served as an example to follow. However, manufacturers sometimes do not hesitate to call their keyboards ergonomic if there is at least one of the three innovations reviewed by the original Microsoft keyboard. Perhaps the only drawback of such keyboards is the space they occupy. If you work a lot with text and you are not limited by space, then get exactly an ergonomic keyboard. It should be noted that they are significantly more expensive than conventional ones.
Later, broken keyboards appeared, allowing you to adjust the angle of rotation of the two halves. Each half has its own feet, so you can still adjust the tilt in different directions. Some went even further and came up with a keyboard, generally consisting of two halves. This can be quite handy, but a keyboard like this is not hacky to put on your lap.
The palm rest introduced in MS Natural Keyboard has now extended to regular keyboards as well. It is designed to rest the hands, and not their working position: according to the rules, the hands should be bent and hang over the keys. That is why it is called Palm Rest (rest of the brushes). However, how many people follow these rules, relying on the table when working with their wrists (I myself am one of them)? For the latter, the stand will be a significant relief, especially in the case of tall keyboards. The stand also enhances the look, especially when done in a different color. The stands are detachable and cast. Understandably, the detachable stand is a more flexible solution, allowing you to painlessly switch to a keyboard without a stand. If the stand is detachable, then it is good that it has an attachment that allows some rotation relative to the attachment line, so that when the keyboard is tilted using the legs, the stand does not break. Choose keyboards with detachable stands. Note that the palm rest is sold separately as an accessory, so owners of keyboards without a palm rest can get one at any time.
2. Keyboard type
Membrane
Semi-mechanical
Mechanical
Name membrane keyboards occurs because when a key is pressed, two membranes are closed. The return of the key is carried out by a rubber dome (with a shaft in the center). Membranes usually look like discs on printed plastic sheeting. An intermediate foil with holes is used to separate the membranes. Therefore, sentences are often written "film" or "membrane keyboard". Since the membranes are located on the inner sides of the films, the structure is well protected, for example, from spilled coffee. In a more secure implementation, everything looks like a single rubber mat with protruding domes located under the keys. The advantages of such keyboards include low noise, ease of pressing the keys, protection from small objects and liquids, and low price. The only drawback is the shorter durability compared to other types.
In the floor mechanical keyboards ah, more durable (up to 50-100 million clicks) and non-rubbing metal contacts are used, in expensive models they can be gold-plated. All this is hosted on printed circuit board... The key is returned by a rubber dome. Otherwise, semi-mechanical keyboards are similar to membrane ones. But they cost a little more.
In mechanical keyboards, the key is returned by a spring. The disadvantages of such a mechanism are the lack of tightness and high cost. For example, cleaning up spilled coffee will take a long time. True, there are models with protection, but they are even more expensive. The advantage is durability and reliability, especially when the contacts are gold-plated, as well as the absence of fatigue (that is, the resistance to pressing is practically independent of the number of clicks, which cannot be said about mechanical and semi-mechanical keyboards).
In my opinion, mechanical keyboards have more disadvantages than advantages. Firstly, they are poorly protected, and secondly, they make more noise than membrane ones, and they are much more expensive. Therefore, it is better to choose between membrane and semi-mechanical. By the way, these keyboards are identical in many respects, so the choice here is often determined by the price. True, semi-mechanical ones are more durable, but an expensive membrane one should also be enough for you (somewhere around 20-30 million clicks for good models) that when it breaks down, then all other computer components will already be in the landfill.
Keyboards come with or without a click. Literally, click is a click. It is realized with an arcuate thin plate under the key, which bends with a jerk. Clicking allows you to accurately feel that the key is pressed and not skip letters when typing. Many users like the click, but it's better to buy a reliably working keyboard and not interfere with your work and other people with all sorts of clicks. Typically, a click is found in mechanical keyboards (since it changes their cost little), but also occurs in other types of keyboards.
There is another type of keyboards - touch keyboards. Its principle of operation is based on the amplification of the potential difference applied to one element. The number of these elements corresponds to the number of keys. Conductive contacts made in the form of two plates separated by a small gap are used as sensitive elements. At the moment the finger touches the contact pads, the statistical potential is amplified by the corresponding circuit, the output of which generates a signal similar to the signal of a conventional keyboard. Touch keyboards are the most durable because there are no mechanical elements in them, but due to this, they are noticeably more expensive than conventional ones. Since the electronics are covered with a layer of polymer film (symbols are also applied on it), the touch keyboard is almost completely protected from external influences. True, such devices have not received any widespread use due to the inconvenience of use and high cost, therefore they can only be found at large industrial enterprises in production workshops, and even then rarely.
Ease of keystroke
In my opinion, the lighter the better. Pressing lightly allows you to type quickly and without missing letters with less effort. When buying, press the keys, compare with other keyboards. Remember that you may have to press these keys quite a lot, so isn't it worth making your life easier?
3. Interface
There are three interfaces: AT, PS / 2 and USB. AT is already outdated and buying a keyboard with such a connector is worth it only if the motherboard is designed to connect such a keyboard.
If you have an ATX motherboard, then it has another keyboard connector called PS / 2. Therefore, choose a keyboard with a PS / 2 connector at the end of the cable.
Recently, devices for the USB bus, including keyboards, have become very popular. In addition to the possibility of hot plugging / unplugging, they have no obvious advantages, but they are much more expensive. But, nevertheless, if you have money, then a keyboard with a USB interface is better than with a PS / 2 (if only because such a keyboard is more modern). By the way, the prices for USB keyboards are dropping all the time and will probably soon be at the level of regular keyboards, which is another plus. However, until it drops enough, there is hardly anything objectively good in USB.
If you are neophytes (that is, you love everything new) and decide in favor of USB, then you need to choose next whether you want to turn the keyboard into a USB hub or not. The fact is that a USB keyboard can have several more USB ports (1, 2, 4) for connecting other peripheral devices with a chain. In my opinion, using the keyboard as a hub is not entirely convenient, since the keyboard sometimes has to be moved, and then all the cables will be pulled behind it, which is inconvenient.
Finally, keyboards come in wireless and wired. Wireless keyboards consist of a keyboard itself and a transceiver that uses high frequency radio waves. There are also transmitters that use infrared radiation, but they are not widely used due to the fact that the device requires direct contact of devices for the operation of the device, and radio keyboards are more common. If you like to play Unreal or type something, lounging in a chair and putting your feet on the table, then wireless keyboards will provide such an opportunity. In other cases, their advantages are controversial, but the disadvantages are obvious - it is necessary to change the batteries, do not obstruct the transmitter with objects through which radio waves do not penetrate well, etc. In addition, such keyboards are much more expensive than conventional ones. And if you just do not have enough cable length, then you can increase it using a keyboard extension cable.
Additional features
Before the advent of Windows, all keyboards had 101 keys. Then three more keys were added: two keys to invoke the Start menu and one key to invoke context menu... It is unlikely that their presence can be considered as additional features, because they have already become standard. But now on keyboards you can find many other additional keys and buttons.
Internet buttons. The rapid development of the Internet has led to the emergence of the corresponding buttons. Usually they perform the following functions: connect to the Internet, go to a given site, make an exchange with the post office. The number of such buttons is different: from zero to two dozen. Buttons are usually located at the very top, above the function keys. If you often use the Internet, then the buttons of the same name will help save you time.
Multimedia buttons. Multimedia means everything here. These buttons allow you to control your media players, including: increase or decrease volume, mute, skip to next / previous track, start playback, pause, end playback, eject disc. Sometimes there are fewer such buttons than the listed functions, and then the buttons are programmed for the current functions. If you often use multimedia players, then you can opt for a keyboard with multimedia buttons. Note that the multimedia buttons have changed the interpretation of the multimedia keyboard: earlier this was the name of a combine with a built-in speaker and volume control (it still exists). Despite the fact that it is hypothetically possible to think of keyboards with separate groups of buttons, in practice keyboards are produced either with only sleep keys or with all of them at once. In the latter case, the keyboard is still called multimedia, so multimedia means the presence of all keys.
Usually, additional buttons are physically implemented, which increases the size and cost of the keyboard. But there is an original solution, when only one button is introduced - the MF (Multimedia Function) switch, which translates 12 function keys into multimedia. Such keyboards are available, for example, from the BTC company. In Genius, the button is called EasyKey, but the meaning is the same. Some inconvenience is the need to switch. Another easy way to add programmable keys is to add one key, which is used in a chord with the existing ones. An example is the Fn key available on some keyboards. Used for Fn + functional chords.
There are also keyboards with various additional input devices. For example, this illustration shows a keyboard with a touch pointer. Personally, I do not understand the purpose similar devices- they are very expensive, and all sorts of mouse replacements are there touch panels all the same they cannot. Try to play Unreal with the help of such a Touch Pad "ah! It is unlikely that you will succeed, and for office applications, the Touch Pad is perhaps not the best solution. Well, unless there is no place to place a mouse ... keyboards with a barcode reader (a trade code that is often found on packaging), they are used for PCs used as cash registers.This keyboard either comes with a reader pencil or has a reader on it. There are also keyboards for the blind , the keys of which have corresponding projections; they, as a rule, are equipped with an output device in the form of a bar in the lower part, divided into squares, inside which there are 6 floating points covered with a layer of rubber. up and press on the rubber layer, which allows a person to identify the information being entered.
In order to reduce the size of some keyboards, some models of keyboards may have a compact number block, when the paging keys are not duplicated, and the block of keys of the Break group is located at the top. Others may not have a digital block at all. Sometimes (if it is not there) it is possible to connect an additional block with numeric keys to the keyboard.
In other cases, the dimensions are reduced by reducing the distance between the keys and / or reducing the thickness of the outer edge. The second method is harmless, but the first one cannot be welcomed in any way, because as the distance between the keys decreases, the likelihood of touching neighboring keys increases when typing. It is even worse when the keys are also reduced in size.
And finally, all sorts of little things, but which are also very important. Firstly, it is a way of applying a pattern to the keys. Nice keyboards have a drawing made with a laser, on cheaper ones it is applied with paint. The second, of course, is worse, although the paint also lasts a very long time.
Pay attention to the presence of clues on the "F" and "J" keys and on the "5" key of the digital block. Although few people know how to use them, but what the hell is not kidding, you may someday learn to type blindly. In addition, in the dark, these protrusions sometimes help to orientate (when the screen is black, turn on the light too lazy, and you need to enter the boot password). So make sure that there are tabs on the keyboard.
One of the requirements for the periphery is their low radiation. This ensures, firstly, health protection, and secondly, which is more important (more precisely, it is much less important, but even the most radioactive keyboard cannot cause visible harm to health), the radio will not crack and hiss near the periphery. There must be compliance with the American FCC standard (part 15, subpart B, class B), which is reflected in the documentation, and also applied to the back of the keyboard. You can ignore this parameter, since any more or less well-known manufacturer produces only such keyboards. For those who like to keep the keyboard on their lap, we recommend models with a metal bottom.
Service keys can be either darker or indistinguishable from alphabetical ones. The choice is determined only by your taste - here the main thing is to like it.
Also pay attention to the apparent quality of the product. If at the very first touch or other external influence the plastic starts to creak, if burrs are visible at the corners, if the inscriptions are clearly inferior, then such a device is hardly worth attention. It is very good if the seller gives a guarantee for his product. Usually it lasts no more than a year, but this is usually quite enough - if the keyboard has worked properly for one year, then, most likely, it will work for a very long time, unless, of course, you level the nails on it and arrange a bath with lavender foam ... , if you spilled coffee on the keyboard, for example, and it stops working, then you can try to take out the board and rinse it under a strong stream of water (of course, you need to dry the board before installing it back). The probability that the keyboard will work is somewhere around 50%.
Along with the keyboard, the mouse is also the most important input device. Actually, these are the buttons located on it. You cannot enter text information using the mouse (unless you take the appropriate keyboard emulator programs), but this is precisely its main advantage.
The principle of operation of mice is very simple: two sensors track the movement of the mouse, respectively, horizontally and vertically, and based on their data, the mouse driver generates the movement of the cursor on the screen.
There are three types of mice. It:
Mechanical, in them the main element is sensors that track the movement of the ball. The sensors are mechanical, hence the name of mice. As a result, the movement of the mouse is not so smooth, and its durability is also small. Therefore, since their quality leaves much to be desired, and the cost price is not much lower than optomechanical mice, almost all manufacturers have stopped producing them.
Optomechanical. Similar to mechanical, but the movement of the ball is tracked by optical sensors. Such mice are quite reliable, versatile (they can work on any flat surface, are cheap, therefore they are very widespread, and they are usually used.
Optical. An optical mouse sends a beam to an opaque surface, and after reflection, the beam goes back to the mouse and is analyzed there by electronics, which, depending on the characteristics of the received signal, tracks the two directions of the mouse movement, based either on the angles of incidence or on some other signs. The advantage of such a mouse is its very high reliability, reliability and smoothness of movement. The downside is perhaps the relatively high price of such a mouse, as well as the fact that you need to keep it pressed against the mat (or other surface) all the time, otherwise the cursor moves wherever it pleases.
I must say that earlier optical mice were used only with a special mat with markings applied to it, which was usually supplied with the mouse itself. Now, advances in this area have made it possible to create optical mice that work on almost any surface. Here, the optical sensor is a kind of video camera, and the processor built into the mouse takes pictures at a certain frame rate and, analyzing the results obtained, determines the direction of mouse movement. The disadvantage of this technology is that if the processor does not have the required speed, then with very fast movements of the manipulator, the cursor begins to behave in an unpredictable manner. However, good (and therefore expensive) mice are usually fine with this. From the peculiarities of use, it can be noted that the optical mouse does not work on transparent and diffractive surfaces, such as window glass or the surface of a CD.
Other important characteristic mouse - a way to connect it to a PC, that is, an interface. Previously, the COM interface was mainly used, but now PS / 2 is the standard. There is no particular difference between them, but you will still be unable to connect anything except a mouse to the PS / 2 port, so a mouse with a 6-pin circular PS / 2 connector is preferable. It should only be noted that very old computers do not have such a connector, and there is only one way out - a mouse for a COM port with a 25 - (less often) or 9-pin socket at the end of the cable.
There are also USB mice that are designed to work with the USB bus. They are better than others, because, firstly, they provide a larger number of readings per unit of time (more on that later), and, secondly, they can be turned on while the computer is running, which is especially important for owners of laptop PCs. True, mice for the COM port are also adapted for hot plugging, but in the case of PS / 2, although it is possible, it is not necessary for the reason that it is very easy to burn the port. Plus, USB mice are more modern. But the price is disappointing ... And until it drops to the level of non-USB mice, in my opinion, it will not be possible to say for sure that USB mice are much better. And if you have an antique computer, then there is only one choice - COM.
Now about the resolution and the readings. Mouse resolution is measured in dpi and shows how many counts (pulses into which the distance traveled is divided) the mouse takes when it travels one inch. Naturally, the larger the better, since the higher the resolution allows you to more accurately position the cursor, and the cursor movement becomes smoother. Normal mouse resolution is 200-900 dpi. In this case, the accuracy, of course, depends on the resolution of the monitor screen and the selected speed. By the way, an increase in speed by setting the corresponding option in the control panel is not associated with an increase in dpi, as some believe, the driver simply maps a larger number of screen pixels to one sample. When working at low resolutions, this is not so important, but at high resolutions the cursor starts moving in noticeable jumps, which is very annoying, especially when working with small objects, so either get a good mouse, or set a low resolution, or slow down the cursor movement.
Optical mice can have a resolution of 1000 dpi or more, so when using them, the cursor can be very accurately positioned even at high screen resolutions and maximum speed of its movement. So if you have the money, opt for optical mice, as they have the highest resolution of any mouse. Unfortunately, the dpi parameter is indicated in few places, but it, as a rule, can be determined by price - the higher it is, the better the mouse is (more precisely, on the contrary: the better the mouse, the higher its price).
Another thing is how many counts the mouse can do in a second. It no longer depends on the mouse, but on the interface. For mice with COM and PS / 2 interfaces, this number is 40, and for USB it is more than 100. This parameter indicates how smoothly the mouse pointer can move when it moves quickly (namely, fast movements of the mouse itself). With slow movements, this parameter does not really matter, since 40 samples per second is quite enough, but when playing, say, in Unreal Tournament, it is very important. Let's say you are playing at 1024x768. Then someone comes up to you from behind and inserts a rocket into the appropriate place. If you are still alive, then in no more than one second you need to turn 360 degrees and retaliate, otherwise you will not be able to do this later. It is easy to calculate that when a mouse is connected to the PS / 2 port, the screen will move in "portions" of at least 25 pixels. And if you make a mistake by 25 pixels when aiming, then it will be a significant miss. True, there are utilities that can overclock the mouse (sounds funny: overclock the mouse) and increase the number of samples per second from 40, say, to 60. But why bother with utilities that only eat up memory and overload the processor, besides possessing good effect Isn't it easier to use a USB mouse that is three times more accurate?
Earlier there were also the so-called Bus Mouse, using the system bus. They were sold with their expansion cards and had a special connector. Now such a solution is outdated and therefore we will not dwell on it in detail. Let's just say that older notebooks may have built-in ports for the Bus Mouse.
If you don't like tailed animals, then there are tailless mouse breeds. Like keyboards, they can use either infrared or radio waves. The latter, of course, are better, since they can work even in the absence of line of sight with the transceiver. Just remember to change the batteries. They say, by the way, that such mice do not work on batteries, because the battery gives 1.2 V instead of the required 1.5. I don’t know, I didn’t check it myself.
A standard mouse has three buttons. Two-button mice are very common, as the third button is hardly used. But most mice have other useful and not-so-useful additions. Most often it is a wheel that allows you to scroll through the contents of the window. Of course, this is more convenient than poking the pointer along the ruler and pulling it down. Therefore, choose a mouse with a wheel. It can be located either on the side or in the middle - each conveniently has a different position. There can also be additional buttons on the mouse (from 1 to 40), which can be assigned different functions. If you do not use them, then I think they are not needed, since they will only interfere.
Another interesting type of mouse is its modification in the form of a phone. The phone is the most common there, plugged into an ordinary telephone socket. So that two wires do not leave the mouse, they are usually combined into one, and the separation into a telephone cable and the mouse cable itself occurs in a separate small block, to which everything is connected. You can speak using the speakerphone without being distracted from the main activity; for this, the “mouse phone” has a speaker and a microphone. Such an original solution is a very good alternative to both conventional and miniature telephone sets, which, for example, are hung on a monitor. Since there is nothing complicated and expensive in these devices, they are also relatively inexpensive (about the same as a phone with the same functions and a similar mouse), so such mice can be very useful for those users who like to talk on the phone not looking up from the screen.
A small variety of mouse-like manipulators is the Trackball, which is essentially the same mouse, only inverted. The movement of the cursor is carried out by the movement of the ball (more precisely, the ball, since its dimensions are larger than that of a mouse). Personally, I find the convenience of such a device questionable (maybe because I just never used it), but it presents a good alternative for those users whose table is filled with coffee cups and other utensils. If you are such a user, then pay attention that the body is massive enough and does not slide on the table, and the ball is large. Trackballs are believed to be particularly useful when working with graphics programs, since they allow you to more accurately position the cursor. It may seem a little strange, but trackballs can also be wireless.
Choose large mice. It is very unpleasant when it constantly falls out of your hands. It is good if it is not too heavy, then it is easier and more pleasant for it to move. And in general, everything should be good in a mouse, because an uncomfortable or poorly working mouse greatly overshadows everything that you would not do with it. The rug should also be large and comfortable. Recently there have been mats with a gel wrist pad, but it seems to me that the extra unevenness only gets in the way. By the way, especially if the mouse is optical, it is very good to use a sheet of paper instead of a mat - it will grip better, and it absorbs all dirt, grease and sweat (very important in the summer when you play Unreal) well. And when it gets dirty, it's easy and not a pity to replace it with a new one.
CRT monitors (Cathode Ray Tube) are the most common type. As the name implies, all such monitors are based on a cathode ray tube, or, as they say in domestic literature, a cathode ray tube (CRT). The technology used in this type of monitor was created many years ago and was originally created as a special instrument for measuring alternating current, in other words, for an oscilloscope. The development of this technology led later to the creation of monitors.
A CRT monitor has a glass tube with a vacuum inside. On the front side, the inner part of the glass of the tube is coated with a luminofor. Rather complex compositions based on rare earth metals - yttrium, erbium, etc. are used as phosphors for non-ferrous CRTs. A phosphor is a substance that emits light when bombarded by charged particles, in this case electrons. Note that sometimes the phosphor is called phosphorus, but this is not true as the phosphor used in the CRT coating has nothing to do with phosphorus. In addition, phosphorus glows as a result of interaction with atmospheric oxygen during oxidation to P2O5 and is short in time. To create an image in a CRT monitor, an electron gun is used, which emits a stream of electrons through a metal mesh onto the inner surface of a glass screen, which is covered with multi-colored phosphor dots. The flow of electrons on the way to the front of the tube passes through an intensity modulator and an accelerating system, operating on the principle of a potential difference. As a result, electrons acquire a large energy, part of which is spent on the glow of the phosphor. Electrons fall on the phosphor layer, after which the energy of the electrons is converted into light, that is. the flow of electrons causes the dots of the phosphor to glow. These luminous dots of the phosphor form the image you see on your monitor. As a rule, in a color CRT monitor, three electron guns are used (each of which illuminates its own phosphor, which can glow in one color - red, green or blue, therefore CRT-based monitors are often called RGB (Red, Green, Blue), but this is not absolutely correct, since the RGB principle is also used in other monitors, as well as in devices that have a very distant relationship to monitors). One gun is used in monochrome monitors, which are now practically not produced and are of little interest to anyone.
To understand how a cathode-ray tube works, it would be nice to remember physics. As already mentioned, it is based on three electron guns that emit electrons. By means of Coulomb forces, these electrons are deflected and thus separate beams of the desired direction are created. A special deflection system deals with the deflection of electrons. When each of the three beams hits its own phosphor, the glow of each of them is obtained. From these three colors, as is known, it is possible theoretically to obtain any color shade by changing the current of each of the three electron beams falling on the triad of points. Theoretically, because it is very difficult to create such a complete system, although in practice good CRTs can create so many colors that it is unlikely that the "average" human eye can distinguish them all. Since the beam is one and very narrow, it is necessary to move the beam across the screen to create a complete frame. Moreover, this must be done quickly enough, since the phosphor dots do not glow for too long, and before they go out, they must be activated again. The ray begins its course from the upper left corner and gradually reaches the lower right.
In order for a CRT to show what is needed, and not what it wants, it needs appropriate control electronics, the quality of which largely determines the quality of the monitor. By the way, it is the difference in the quality of control electronics created by different manufacturers that is one of the criteria that determines the difference between monitors with the same cathode-ray tube. It is understood that the electron beam, for example for red phosphor elements, should not affect the green or blue phosphor. To achieve this, a special mask is used, whose structure depends on the type of CRTs from different manufacturers, although, probably, the type of CRT (as well as its cost, image quality and other parameters) depends on the type of mask. CRTs can also be divided into two more classes - with delta-shaped arrangement of electron guns and with planar arrangement of electron guns. Various masks can be used in these tubes, this will be discussed later. At the same time, tubes with a planar arrangement of electron guns are also called kinescopes with self-alignment of beams, since the effect of the Earth's magnetic field on three planar beams is practically the same, and when the position of the tube relative to the Earth's field changes, additional adjustments are not required.
The shadow mask is the most common type of mask for CRT monitors. The shadow mask consists of a metal mesh in front of the glass part of the tube with a phosphor layer. Typically, most modern shade masks are made from Invar (an alloy of iron and nickel). The holes in the metal mesh work like a sight (although not entirely accurate), and this is what ensures that the electron beam hits only the required phosphor elements, and only in certain areas. The shadow mask creates a lattice with uniform circular holes through which the electron beams pass. The name "shadow" is not entirely correct, because the masks considered below will also be shadow, but traditionally a mask in the form of a lattice with round holes is usually called shadow. Since the shadow mask is quite cheap and gives good image quality, picture tubes with it are the most popular. The shadow mask is used in most monitors from Hitachi, Panasonic, Samsung, Daewoo, LG, Nokia, Viewsonic, etc.
The slot mask is a technology widely used by NEC under the name CromaClear. In this case, the phosphor elements are arranged in vertical elliptical cells, and the mask is made of vertical lines. In fact, the vertical stripes are divided into elliptical cells that contain groups of three phosphor elements in three primary colors. The minimum distance between two cells is called slot pitch. The size of the cells can be different horizontally and vertically. The lower the slot pitch value, the naturally higher the image quality on the monitor. The slit mask is used, in addition to monitors from NEC (where the cells are elliptical), in Panasonic monitors with a PureFlat tube (formerly called PanaFlat). By the way, the very first flat-tube monitor was a Panasonic with a PanaFlat tube. LG in its monitors uses a flat slit tube Flatron with a pitch of 0.24 mm (this technology has nothing to do with Trinitron, about which you read below). Note that Samsung's Infinite Flat Tube (DynaFlat series) does not use a slit mask, but a regular shadow mask. Slit mask tubes are generally completely flat and give better image quality than shadow mask tubes.
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