Exam Time for IT. Ч.1. Практикум

Topic 8. Types of computers and their peripherals.

The types of computers range from the Hybrid to the Analog types. The computers you come across in the daily course of your day range from laptops, palmtops and towers, to desktop computers, to name a few. But the very word «computers» reminds one of the desktop computers used in offices or homes. Different categories of computers have been devised in keeping with our varied needs. According to the classification based on operational principle the types of computers: analog and hybrid.

Analog Computers: The Analog computer is almost an extinct type of computer these days. It is different from a digital computer in respect that it can perform numerous mathematical operations simultaneously. It is also unique in terms of operation as it utilizes continuous variables for the purpose of mathematical computation. It utilizes mechanical, hydraulic, or electrical energy or operation.

Hybrid computers: These types of computers are, as the name suggests, a combination of both Analog and Digital computers. The Digital computers which work on the principle of binary digit system of «0» and «1» can give very precise results. But the problem is that they are too slow and incapable of large scale mathematical operation. In the hybrid types of computers the Digital counterparts convert the analog signals to perform Robotics and Process control.

Apart from this, computers are also categorized on the basis of physical structures and the purpose of their use. Based on capacity, speed and reliability they can be divided into three categories of computers:

1.The Mainframe Computer — These are computers used by large organizations like meteorological surveys and statistical institutes for performing bulk mathematical computations. They are core computers which are used for desktop functions of over one hundred people simultaneously.

2.The Microcomputer — These are the most frequently used computers better known by the name of «Personal computers». This is the type of computer meant for public use.

A desktop is a PC that is not designed for portability. The expectation with desktop systems is that you will set the computer up in a permanent location. Most desktops offer more power, storage and versatility for less cost than their portable brethren.

Laptops, also called notebooks, are portable computers that integrate the display, keyboard, a pointing device or trackball, processor, memory and hard drive all in a batteryoperated package slightly larger than an average hardcover book.

Palmtops, more commonly known as Personal Digital Assistants (PDAs), are tightly integrated computers that often use flash memory instead of a hard drive for storage. These computers usually do not have keyboards but rely on touchscreen technology for user input. Palmtops are typically smaller than a paperback novel, very lightweight with a reasonable battery life. A slightly larger and heavier version of the palmtop is the handheld computer.

A tablet PC is a notebook or slate-shaped mobile computer, first introduced by Pen Computing in the early 90s with their PenGo Tablet Computer and popularized by Microsoft. Its touchscreen or graphics tablet/screen hybrid technology allows the user to operate the computer with a stylus or digital pen, or a fingertip, instead of a keyboard or mouse. The form factor offers a more mobile way to interact with a computer. Tablet PCs are often used where normal notebooks are impractical or unwieldy, or do not provide the needed functionality.

A workstation is a desktop computer that has a more powerful processor, additional memory and enhanced capabilities for performing a special group of task, such as 3D Graphics or game development.

3.The Mini computer — Mini computers like the mainframe computers are used by business organization. The difference being that it can support the simultaneous working of up to 100 users and is usually maintained in business organizations for the maintenance of accounts and finances.

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Yet another category of computer is the Super Computers. It is somewhat similar to mainframe computers and is used in economic forecasts and engineering designs. Today life without computers is inconceivable. Usage of different types of computers has made life both smooth and fast paced.

Peripherals are components which allow humans to interface with computers.

Display Device. Display devices include computer monitors and other display devices. CRTs and LCDs are common. LCDs are a more recent development, and are gradually replacing CRTs as they become more affordable. LCD’s in addition to being lighter also use less energy and generate less heat.

Sound Output. Sound output includes internal or external speakers and headphones. Mouse. A mouse is a user interface device that can enable different kinds of control than a

keyboard, particularly in GUIs. It was developed at the Xerox PARC (Palo Alto Research Center) and adopted and made popular with the Apple Mac. Today, nearly all modern operating systems can use a mouse. Most mice (sometimes the plural is ‘mouses’ to prevent confusion with the rodent) are made from plastic, and may use a ball to track movement, a LED light, or a laser. Today you can get a wireless mouse that allows you to easily give a presentation without being tied to a desk. These mouses are usually LED or Laser based tracking.

In 1964 the first prototype computer mouse was made to use with a graphical user interface (GUI), windows. Douglas Engelbart received a patent for the wooden shell with two metal wheels (computer mouse U.S. Patent # 3,541,541) in 1970, describing it in the patent application as an «X-Y position indicator for a display system.» It was nicknamed the mouse because the tail came out the end, Engelbart revealed about his invention. His version of windows was not considered patentable (no software patents were issued at that time), but Douglas Engelbart has over 45 other patents to his name.

Keyboard. A keyboard is an input device which is connected to a computer and used to type instructions or information into the computer. Typically, a keyboard has about 100 or so keys. Keyboards differ between languages. Most English-speaking people use what is called a QWERTY layout. This refers to the order of the top row of keys. Some foreign languages (i. e. German) use QWERTZ, where the Z and Y are switched. Many laptop computers do not include a number pad. (There is sometimes a function on the keyboard to enable a numpad-like mode.) Modem keyboards sometimes have extra controls such as volume, and keys that can be programmed to bring up programs of the user’s choice.

Printer. A printer makes marks on paper. It can print images and text. The most common types of printers today are:

Laser printer prints very crisp text, but cheaper models can only print in black and white. Good for places like offices where high printing speed is needed.

Color inkjet printer: Prints photos and other images in color (using 4 colors of ink — cyan, magenta, yellow, and black), but the text they print is often not as crisp as a laser printer.

The average printer of the early 1990s would connect to a computer through its parallel port. To connect it to the computer via parallel port, one would have to screw it into the port. Today many printers are connected through USB. This is because it is easier to connect and remove through a simple plug and play system. It also allows for faster transfer speeds than parallel.

Scanner. A scanner is a device for digitizing paper documents into images that may be manipulated by a computer. The two main classes of scanner are:

hand-held scanners (in which the user manually drags a small scanning head over the document);

• flat-bed scanners (which is designed to accommodate a whole sheet of paper, which is then examined by a motorized scanning head).

If the original document contained text, Optical Character Recognition (OCR) software may be used to reconstruct the text of the document from the scanned images.

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Modem. A contraction of «Modulator — demodulator», a modem allows a computer to communicate over an analogue medium (most commonly a telephone line). The modem encodes digital signals from the computer as analogue signals suitable for transmission (modulation) and decodes digital data from a modulated analogue signal (demodulation). Using modems two computers may communicate over a telephone line, with the data passed between them being represented as sound.

Modems are usually involved with dial-up internet services. As broadband catches on, they are falling into disuse. However, the devices used to connect to broadband connections are also called modems, specifically DSL Modems or Cable Modems.

Questions for self-check:

Which types of computers are there in terms of the classification based on operational principle?

How can computers be classified according to the principle of physical structures and the purpose of their use?

What is the difference between analog and hybrid computers?

What are the most common types of printers?

What's a scanner?

Exercises:

1. Give English-Russian equivalents of the following words and expressions:

tower; suggest; точный, определенный; robotics; наблюдение, обозрение, обзор; frequently; настольный компьютер; tablet; основная масса, большая часть чего-л.; reliability; основной, базовый; incapable; немыслимый; come across; simultaneously;

исходя из, на основе; in respect that; устаревший, вышедший из употребления; Personal Digital Assistant; зачастую, часто; laptop; precise; аводить на мысль,

говорить о, означать; variable; крупный масштаб; extinct; (случайно) встретиться с кем-л., натолкнуться на что-л.; core; desktop; надёжность; large scale; одновременно, совместно; неспособный к чему-л.,на что-л.; bulk; fast расе; карманный компьютер; in terms of; smooth; учитывая, принимая во внимание; survey; переменная (величина); inconceivable; робототехника; palmtop;

персональный цифровой секретарь; handheld PC.

2.Choose the most suitable words from those given in brackets without consulting the text. Translate the sentences into Russian:

1.The analog computer is almost (a precise, an extinct) type of computer these days.

2.The digital computers are too slow and (inconceivable, incapable) of large scale mathematical operation.

3.Based on speed and (capacity, large scale, reliability) they can be divided into three categories of computers.

4.Mainframe computers are (core, bulk) computers which are used for desktop functions of over one hundred people (simultaneously, frequently).

5.Mini computers can support the (simultaneous, smooth) working of up to 100 users.

6.The Super Computer is somewhat similar to mainframe computers and is used in economic (forecasts, surveys).

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Topic 9. Operating system

An operating system (commonly abbreviated as OS and O/S) is the software component of a computer system that is responsible for the management and coordination of activities and the sharing of the resources of the computer. The operating system acts as a host for application programs that are run on the machine. As a host, one of the purposes of an operating system is to handle the details of the operation of the hardware. This relieves application programs from having to manage these details and makes it easier to write applications. Almost all computers, including hand-held computers, desktop computers, supercomputers, and even modern video game consoles, use an operating system of some type. Some of the oldest models may however use an embedded OS, that may be contained on a compact disk or other storage device.

Operating systems offer a number of services to application programs and users. Applications access these services through application programming interfaces (APIs) or system calls. By invoking these interfaces, the application can request a service from the operating system, pass parameters, and receive the results of the operation. Users may also interact with the operating system by typing commands or using a graphical user interface (GUI). For handheld and desktop computers, the GUI is generally considered part of the operating system. For large multi-user systems, the GUI is generally implemented as an application program that runs outside the operating system.

Common contemporary operating systems include Microsoft Windows, Mac OS X, Linux and Solaris. Microsoft Windows has a significant majority of market share in the desktop and notebook computer markets, while servers generally run on Linux or other Unix-like systems. Embedded device markets are split amongst several operating systems.

Technology

An operating system is a collection of technologies which are designed to allow the computer to perform certain functions. These technologies may or may not be present in every operating system, and there are often differences in how they are implemented. However, as stated above, most modern operating systems are derived from common design ancestors, and are therefore basically similar.

Boot-Strapping

In most cases, the operating system is not the first code to run on the computer at startup (boot) time. The initial code executing on the computer is usually loaded from firmware, which is stored in read only memory (ROM). This is sometimes called the BIOS or boot ROM.

The firmware loads and executes code located on a removable disk or hard drive, and contained within the first sector of the drive, referred to as the boot sector. The code stored on the boot sector is called the boot loader, and is responsible for loading the operating system’s kernel from disk and starting it running.

Some simple boot loaders are designed to locate one specific operating system and load it, although many modern ones have the capacity to allow the user to choose from a number of operating systems.

Program Execution

An operating system’s most basic function is to support the running of programs by the users. On a multiprogramming operating system, running programs are commonly referred to as processes. Process management refers to the facilities provided by the operating system to support the creation, execution, and destruction of processes, and to facilitate various interactions, and limit others.

The operating system’s kernel in conjunction with underlying hardware must support this functionality. Executing a program involves the creation of a process by the operating system. The kernel creates a process by setting aside or allocating some memory, loading program code from a disk or another part of memory into the newly allocated space, and starting it running.

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Operating system kernels store various information about running processes. This information might include:

a unique identifier, called a process identifier (PID);

a list of memory the program is using, or is allowed to access;

the PID of the program which requested its execution, or the parent process ID (PPID);

the filename and/or path from which the program was loaded;

a register file, containing the last values of all CPU registers;

a program counter, indicating the position in the program.

Interrupts

Interrupts are central to operating systems as they allow the operating system to deal with the unexpected activities of running programs and the world outside the computer. Interruptbased programming is one of the most basic forms of time-sharing, being directly supported by most CPUs. Interrupts provide a computer with a way of automatically running specific code in response to events. Even very basic computers support hardware interrupts, and allow the programmer to specify code which may be run when that event takes place.

When an interrupt is received, the computer’s hardware automatically suspends whatever program is currently running by pushing the current state on a stack, and its registers and program counter are also saved. This is analogous to placing a bookmark in a book when someone is interrupted by a phone call. This task requires no operating system as such, but only that the interrupt be configured at an earlier time.

In modem operating systems, interrupts are handled by the operating system’s kernel. Interrupts may come from either the computer’s hardware, or from the running program. When a hardware device triggers an interrupt, the operating system’s kernel decides how to deal with this event, generally by running some processing code, or ignoring it. The processing of hardware interrupts is a task that is usually delegated to software called device drivers, which may be either part of the operating system’s kernel, part of another program, or both. Device drivers may then relay information to a running program by various means.

A program may also trigger an interrupt to the operating system, which is very similar in function. If a program wishes to access hardware for example, it may interrupt the operating system’s kernel, which causes control to be passed back to the kernel. The kernel may then process the request which may contain instructions to be passed onto hardware, or to a device driver. When a program wishes to allocate more memory, launch or communicate with another program, or signal that it no longer needs the CPU, it does so through interrupts.

Protected Mode and Supervisor Mode

Modern CPUs support something called dual mode operation. CPUs with this capability use two modes: protected mode and supervisor mode, which allow certain CPU functions to be controlled and affected only by the operating system kernel. Here, protected mode does not refer specifically to the 80286 (Intel’s x86 16-bit microprocessor) CPU feature, although its protected mode is very similar to it. CPUs might have other modes similar to 80286 protected mode as well, such as the virtual 8086 mode of the 80386 (Intel’s x86 32-bit microprocessor or i386).

However, the term is used here more generally in operating system theory to refer to all modes which limit the capabilities of programs running in that mode, providing things like virtual memory addressing and limiting access to hardware in a manner determined by a program running in supervisor mode. Similar modes have existed in supercomputers, minicomputers, and mainframes as they are essential to fully supporting UNIX-like multi-user operating systems.

When a computer first starts up, it is automatically running in supervisor mode. The first few programs to run on the computer, being the BIOS, bootloader and the operating system have unlimited access to hardware. However when the operating system passes control to another program, it can place the CPU into protected mode.

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In protected mode, programs may have access to a more limited set of the CPU’s instructions. A user program may leave protected mode only by triggering an interrupt, causing control to be passed back to the kernel. In this way the operating system can maintain exclusive control over things like access to hardware and memory.

The term «protected mode resource» generally refers to one or more CPU registers, which contain information that the running program isn’t allowed to alter. Attempts to alter these resources generally causes a switch to supervisor mode.

Questions for self-check:

What are the purposes of an operating system?

How may users interact with operating systems?

The operating system is the first code to run on the computer at startup (boot) time, isn’t it? Speak on the steps of bootstrapping.

What facilities are provided by the operating system?

What is a process? How is it created?

Where is various information about running processes stored? What does it include?

What is interrupt-based programming required for?

How are interrupts processed?

What does dual mode operation supported by modern CPUs mean?

Exercises:

1. Give English-Russian equivalents of the following words and expressions:

current state; драйвер устройства; supervisor mode; освобождать; allocate;

запускать, активировать; cause; запрашивать; launch; разделять; host; attempt; предшественник; boot (bootstrap); request; изменять(ся); переделывать; relieve; размещать, распределять; counter; relay; прерывание; invoke; режим разделения времени; ancestor; приостанавливать, откладывать (на более позднее время); time sharing; текущее состояние; запускать, инициировать; split; передавать, ретранслировать; device driver; (начальная) загрузка; запускать; protected mode; защищенный режим; хост; trigger; привилегированный режим (процессора); alter; счетчик; suspend; попытка, проба; interrupt; быть причиной, вызывать.

2.Find the word belonging to the given synonymic group among the words and word combinations from the previous exercise:

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Topic 10. Computer networking

Computer networking is the engineering discipline concerned with communication between computer systems or devices. Networking, routers, routing protocols, and networking over the public Internet have their specifications defined in documents called RFCs. Computer networking is sometimes considered a sub-discipline of telecommunications, computer science, information technology and/or computer engineering. Computer networks rely heavily upon the theoretical and practical application of these scientific and engineering disciplines.

A computer network is any set of computers or devices connected to each other with the ability to exchange data. Examples of networks are:

local area network (LAN), which is usually a small network constrained to a small geographic area;

wide area network (WAN) that is usually a larger network that covers a large geographic area;

wireless LANs and WANs (WLAN & WWAN) is the wireless equivalent of the LAN and WAN.

All networks are interconnected to allow communication with a variety of different kinds of media, including twisted-pair copper wire cable, coaxial cable, optical fiber, and various wireless technologies. The devices can be separated by a few meters (e.g. via Bluetooth) or nearly unlimited distances (e.g. via the interconnections of the Internet).

Views of Networks

Users and network administrators often have different views of their networks. Often, users share printers and some servers form a workgroup, which usually means they are in the same geographic location and are on the same LAN. A community of interest has less of a connotation of being in a local area, and should be thought of as a set of arbitrarily located users who share a set of servers, and possibly also communicate via peer-to-peer technologies.

Network administrators see networks from both physical and logical perspectives. The physical perspective involves geographic locations, physical cabling, and the network elements (e.g., routers, bridges and application layer gateways that interconnect the physical media. Logical networks, called in the TCP/IP architecture subnets, map onto one or more physical media. For example, a common practice in a campus of buildings is to make a set of LAN cables in each building appear to be a common subnet, using virtual LAN (VLAN) technology.

Both users and administrators will be aware, to varying extents, of the trust and scope characteristics of a network. Again using TCP/IP architectural terminology, an intranet is a community of interest under private administration usually by an enterprise, and is only accessible by authorized users (e.g. employees). Intranets do not have to be connected to the Internet, but generally have a limited connection. An extranet is an extension of an intranet that allows secure communications to users outside of the intranet (e.g. business partners, customers).

Informally, the Internet is the set of users, enterprises, and content providers that are interconnected by Internet Service Providers (ISP). From an engineering standpoint, the Internet is the set of subnets, and aggregates of subnets, which share the registered IP address space and exchange information about the reachability of those IP addresses using the Border Gateway Protocol. Typically, the human-readable names of servers are translated to IP addresses, transparently to users, via the directory function of the Domain Name System (DNS).

Over the Internet, there can be business-to-business (B2B), business-to-consumer (B2C) and consumer-to-consumer (C2C) communications. Especially when money or sensitive information is exchanged, the communications are apt to be secured by some form of communications security mechanism. Intranets and extranets can be securely superimposed onto the Internet, without any access by general Internet users, using secure Virtual Private Network (VPN) technology.

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When used for gaming one computer will have to be the server while the others play through it.

Networking Methods

Networking is a complex part of computing that makes up most of the IT Industry. Without networks, almost all communication in the world would cease to happen. It is because of networking that telephones, televisions, the internet, etc. work.

One way to categorize computer networks is by their geographic scope, although many real-world networks interconnect Local Area Networks (LAN) via Wide Area Networks (WAN) and wireless networks (WWAN). These three (broad) types are:

Local Area Network (LAN)

A local area network is a network that spans a relatively small space and provides services to a small number of people. Depending on the number of people that use a Local Area Network, a peer-to-peer or client-server method of networking may be used. A peer-to-peer network is where each client shares their resources with other workstations in the network. Examples of peer-to-peer networks are: small office networks where resource use is minimal and a home network. A client-server network is where every client is connected to the server and each other. Client-server networks use servers in different capacities. These can be classified into two types: single-service servers, where the server performs one task such as file server, print server, etc.; while other servers can not only perform in the capacity of file servers and print servers, but they also conduct calculations and use these to provide information to clients (Web/Intranet Server). Computers are linked via Ethernet cable, can be joined either directly (one computer to another), or via a network hub that allows multiple connections.

Historically, LANs have featured much higher speeds than WANs. This is not necessarily the case when the WAN technology appears as Metro Ethernet, implemented over optical transmission systems.

Wide Area Network (WAN)

A wide area network is a network where a wide variety of resources are deployed across a large domestic area or internationally.

An example of this is a multinational business that uses a WAN to interconnect their offices in different countries. The largest and best example of a WAN is the Internet, which is a network comprised of many smaller networks. The Internet is considered the largest network in the world. The PSTN (Public Switched Telephone Network) also is an extremely large network that is converging to use Internet technologies, although not necessarily through the public Internet.

A Wide Area Network involves communication through the use of a wide range of different technologies. These technologies include Point-to-Point WANs such as Point-to-Point Protocol (PPP) and HighLevel Data Link Control (HDLC), Frame Relay, ATM (Asynchronous Transfer Mode) and Sonet (Synchronous Optical Network). The difference between the WAN technologies is based on the switching capabilities they perform and the speed at which sending and receiving bits of information (data) occur.

Metropolitan Area Network (MAN)

A met network is a network that is too large for even the largest of LAN’s but is not on the scale of a WAN. It also integrates two or more LAN networks over a specific geographical area (usually a city) so as to increase the network and the flow of communications. The LAN’s in question would usually be connected via «backbone» lines.

Wireless Networks (WLAN, WWAN)

A wireless network is basically the same as a LAN or a WAN but there are no wires between hosts and servers. The data is transferred over sets of radio transceivers. These types of networks are beneficial when it is too costly or inconvenient to run the necessary cables. The media access protocols for LANs come from the IEEE.

The most common IEEE 802.11 WLANs cover, depending on antennas, ranges from hundreds of meters to a few kilometers. For larger areas, either communications satellites of

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