Summary of Computer Components PDF

‫تلخيص حاسب‬ ‫القسم النظري‬ ‫شهد الغامدي‬  1 COMPUTERS AND HARDWARE Computers: are information processing machines used in different departments and organisations and they can connected all over the world The bene ts of computers: 1 leading...

‫تلخيص حاسب‬ ‫القسم النظري‬ ‫شهد الغامدي‬  1 COMPUTERS AND HARDWARE Computers: are information processing machines used in different departments and organisations and they can connected all over the world The bene ts of computers: 1 leading to more productivity 2- good quality 3- less cost 4- legal construction Computers perform 4 main operation: 1- Receiving input ( Data raw facts) 2- storing data 3- processing the data 4- producing output ( information, which is meaningful data) Computer systems 1- Hardware: physical component like screens, keyboards and printers. The hardware is useless without software. 2- Software:A set of instructions that tell the computer what to do, and how to do it. 3- Users: persons who use the software on the computer to perform some tasks. Information Technology (IT): A set of tools that are used to: receive, process, store and transmit data in an electronic form through all computers. These tools include: hardware, software and connectivity. Types of Computers: Computers are classi ed according to their capacity and performance into the following categorise: 1- Super computers: are high capacity computers that cost millions of dollars and are often used for research. They are used in weather forecasting , oil, exploration and aircraft design. 2- Mainframes: a room sized expensive and high-speed computers that are very powerful with large storage capacities.They occupy special air-conditioned rooms and are used in banks, government departments and large organisations. they are connected to a larger number of terminals that could be 1- dumped (cannot operate on their own) or 2- intelligent terminals (have a processing power themselves that can be used by the user) 3- Mini Computers: ( also known as midrange computers): do the same jops performed by a mainframes but on a smaller scale. They are used by medium-sized companies for speci c purposes such as accounting where personal computers would be inadequate 4- Microcomputers: are the most widely used and fastest- growing type of computers. They are relatively inexpensive and less powerful than large computers. A more common term for microcomputers is Personal Computers or PC Microcomputers are designed for individual users. There are four types of Microcomputers: 1- desktop 2- laptop (notebook) 3- tablet 4- handheld computers fi fi fi 1- Desktop: small enough to t on top of a desk in of ces and at home. They are still very popular because they are fast cheap and have as large capacity. 2- Laptops(Notebook): are small briefcase-sized and portable computers. They have a small screen and a small keyboard. They are as powerful as PCs and they are more expensive then them 3- Tablet Computers: are a small computers that are simpler than Laptops. They have a small screen and a small keyboard. They perform some special functions and are considered to be cheap. 4- Handheld Computers: are the smallest and are designed to t into the palm of one’s hand. Examples of handheld computers include : a) Personal Digital Assistant(PDA): are small pen controlled and handheld computers, instead of pecking at a tiny keyboard. You can use a special pen to write out Commands on the computer screen using PDAs. They can be used to send and receive faxes and emails to write memos and to keep an appointment calendar. b) Smartphones: is a mobile phone with PC-like functionalities. It runs complete operating system software providing a standardized interface for application developers. It has advanced features like email checking, Internet sur ng a built in camera and the ability to play music and read the documents.Some smart phone have keyboards built into them, while other have a touch screen Main parts of personal computers: System Unit (chassis or case): is the container which houses most of the electronic components that make up a computer system such as a CPU and RAM System board (Motherboard): is a at circuit board that controls communications for the entire computer system. Every component inside the system unit is connected to the mother board. The main physical components of a PC are: Central processing unit (processor,CPU): the most important part in a PC. It performs all calculations and determines how fast your computer will run. The CPU speed is measured by Megahertz (MHz) or Gigahertz (GHz) the faster the speed is the more instructions the processor will perform. A CPU on a chip is called a microprocessor.The CPU has two units: A. Control Unit: which is responsible for controlling all computer units B. Arithmetic logic unit(ALU): which performs arithmetic operations such as addition and subtraction operations and logical operations like comparison operations. Bus lines: which are a collection of wires through which data is transmitted from one part of a computer to another. For example the data bus transfers data between the microprocessor and RAM chips. The size of a bus known as it’s width is important because it determines how much data can be transmitted at one time. For example a 16-bit bus can transmit 16 bits of data whereas a 32-bit bus can transmit 32 bits of data. Sockets: which provide a connection point for small electronic parts called chips including the microprocessor and memory chips. Expansion slots: which provide a connection point for specialized cards. For example a wireless networking card plugs into an expansion slot to provide a connection to a Local Area Network (LAN) Ports: any piece of hardware that is connected to a computer to perform a special task is called a Peripheral. Most peripheral connect through a port on the back of the system unit. fi fl fi fi fi The most important and known type of ports is: Universal Serial Bus (USB) :is designed to connect multiple peripherals, such as the keyboard, mouse, printer, scanner and digital camera. It provides the connected device with a small amount of electrical power. Hence, there is no need to use other power supplies when using the (USB) port Memory or the main memory: is the part of the computer where data and programs are stored(temporarily), until they are no longer needed Data processing When data is entered into the computer it is processed according to a set of instructions and then the information comes out. A computer goes through the following steps: 1. Information and programs are entered into the computer through input devices such as the keyboard 2. The data is stored in RAM 3. The processor takes data from RAM and processes it through a program 4. The results are stored in another location in RAM 5. The processed data is transferred from the memory to the monitor or printer 6. The processed data is written to a hard disk, oppy disk or optical disc. The data processing steps discussed above are called the machin cycle Input Devices Input Devices: allow you to input data to the computer. Keyboard: contains the standard typewriter keys plus a number of specialized keys. The standard keys are used to enter words and numbers. Examples of specialized keys are called (function keys) Wireless keyboard: works just like a television remote control device; the computer receives input signals and sends them to the CPU for quick processing and then they are displayed on the computer monitor as the nal result Mouse: controls the screen cursor. The cursor is the symbol on the screen that shows where data may be entered next. It has usually two buttons and performs many actions. It works when any of the buttons is pressed down. A wireless mouse transmits infrared or radio signals to a receiver Trackball: is the mouse turned upside down. The user rotates the ball with ngers to move the cursor on the screen. It saves the space, which is taken up by the mouse and the mouse mat. Touch pad: is a touch sensitive device. When the nger moves on its surface, the cursor of the screen will move. It is used in laptops and in some keyboards. Scanners: convert page contents, taxts, images, pictures, graphics, and other forms of content into electronic signals. These signals can then be stored in a computer and manipulated. They can be: Flatbed: (scanners, which scan a single document at a time Document scanners: scan multiple documents at a time Portable: scanners are handheld ones Optical- character Recognition (OCR): especially preprinted characters are read by the OCR reader as images. To convert the image to characters, you need to buy an OCR software. Magnetic card reader (MCR): information is stored on a thin magnetic strip on the back of the card. This information is read when swiped through a magnetic card reader. fi fl fi fi  Magnetic Ink character recognition (MICR): is used by banks to read, magnetically, encoded characters on the bottom of checks. Optical-mark recognition (OMR): devices sense the preasence or absence of marks. They are commonly used for standardized and multiple choice test scoring. Bar code readers (BCR):or bar code screeners read bar codes or vertical zebra striped marks printed on product containers, and then convert them into texts that can be read. Joystick: is a small hand-lever that can be moved in any direction to control the movement on the screen. it can include buttons to perform some actions and it’s used for playing games on the computer. Microphone: is used to record sounds on the computer, and it allows speech to enter the computer. The spoken sound is then converted to a text using a word processor. Digital camera: it’s similar to ordinary camera, but its uses a ash memory to save images. Well Camera: is a small digital camera are used by people to communicate via Internet. Output devices: Allow you to output information from the computer. The main output devices include the following: Monitors: which the display the results of processing through diplaying texts, graphics, images, forms and so on. The size of monitors is always measured diagonally from one corner to another corner. There are two types of monitors: Traditional computer monitors: which are similar in size and technology to television. The disadvantage is that they are heavy and occupy a space on the desktop. Flat-Panel display monitors: thinner and require less power to operate. however, they are expensive. Projectors: are connected to computer to the display outputs on large boards. They are used in business for training and presentation and in education. Speakers: are used in Multimedia to produce sounds. They can be used either with loudspeakers or with headphones or can be built into the unit. Printers: translate the information processed by the system unit and present information on a paper.The printed output is often called a (hard copy printers) printers have some distinguishing features such as: resolution ( dots per inch- dpi; the higher the dpi, the better the quality of images produced). There are different types of printers, among them are: Laser printers: which use a technology is similar to the one used in a photocopying machine. They use a laser, light beam and an ink-like toner. They produce a high print quality at high speed and are very quiet. The coloured laser printer is very expensive. Inkjet: sprays one or more colours of small droplets of ink at high-speed onto paper. It’s running cost is high. it’s lower than laser printers Cloud printers: are printers which are connected to the Internet and provide printing services on the Internet. An example of this type of sprinters is: Google Cloud printer. 3-D printers: These printers can print 3-D models Computer memory Computers store data in a storage media called memory. There are two types of computer’s memory: 1. Primary memory 2. Secondary memory fl 1. Types of Primary memory: RAM: which is the main memory in a computer. It’s the place where data and programs are stored(temporarily), until they are no longer needed. It consist of locations to store data and the addresses of these locations.RAM is volatile which means that the data is only there while the power of the computer is turned on(when the computer is shut off the content ofRAM is it erased). RAM’s storage capacity is measured in Gigabyte while at speed is measured in Megahertz. Read Only Memory (ROM): is another type of primary memory, but with a very small capacity. It keeps instruction which make the computer work when, turning it on the computer cannot write or store on it. Since ROM cannot be modi ed, it is only suitable for storing data which is not expected to need modi cation at all. Therefore, the use of ROM to store such a small amount of data has disappeared, almost completely in modern general purpose computer and it has been replaced by the (Flash Memory) that can be reprogrammed and on which the data stored can be erased. Flash Memory: it’s a memory that can’t save and erase data in a fast way it is a non-volatile memory (like ROM) and can store and change data (as RAM) but it is faster than RAM. It is used in many devices such as smart phones, laptops and digital cameras. Memory Capacity Measurement: Memory is one of the most important parts of the computer. If the memory has enough space the computer will be fast the most commonly used to measure data storage are shown in the table: 2. Secondary memory Secondary storage devices: to keep software, programs and data permanently you have to save your work on the secondary storage devices before shutting down your computer. Internal hard disks: are locked within the system unit. They are the most important storage media in the computer system. They are thin but rigid metal platters which are covered with a substance that allows data to be held in the form of magnetized spots. Hard disk preform, data storage by rotating platters and they have read/write heads that move in and out. Hard disks are tightly Sealed.within an enclosed unit to prevent any foreign matter from getting inside. Hard on disks are used to store programs and large data les. They are very rst, and their capacity is measured by Terabytes (TB). External hard disks: are disks connected to a USP port on the system unit. They are ideal for backup data and are slower but more expensive than internal disks. They have the same capacity which the internal disks have. Optical disks: in optical disk technology, a laser the surface of a plastic or metallic disk to represent data. The most widely used optical disk or the following: The Compact Disk: is an optical disk which uses laser to read information. They have capacity to 700 MB. They are the three types of comeback desk: fi fi fi fi  CD-ROM: which stands for compact Disk read only memory, is similar to a commercial music CD. The term Read Only means that the disk cannot be written to, and the data on this cannot be erased by the user. CD-ROMs are used to distribute large databases and reference box and to distribute large software application packages. Write Once CD-R: which stands for CD-Recordable can be written to once. After that, they can be read many times without deterioration but cannot be written to nor can the user erase the information stored on them. Rewritable CD-RW: stands for compact Disk Rewritable this disks are very similar to CD-R except that you can change the data stored on them, erase it, or add to it. Digital versatile disk (DVD): is a high capacity development of CD-ROMs. Its capacity as measured by (GB). it is used to store high quality lms and videos, the basic types of DVDs which are similar to CDs are: read only, right ones, and Rewritable. Blu-ray Disks (BD): have high capacity compared to the digital disks (DVD). The name comes from the blue-colored laser technology that is used to read the disk. They have a typical capacity of 50 GB on one side. There are three types of Blu-ray Discs: BD-ROM, BD-R, BD- RW Solid-State Storage: Unlike hard drives, which spin their records and internal moving heads to read and write, the parts of the Solid-State disks are xed and do not move. In spite of their high storage capacity and cheap price, the hard disks face the following problems: The spam sound that is aired as a result of the calendar rotation process during the read and write operations The impact magnetism where the data is exposed to damage, if exposed to a magnetic current. The high energy-consuming which shortnes the life of the device’s battery Heavy weight - SSD has emerged to replace the hard drive problems through the following features: 1. High speed 2. No noise 3. It’s not affected by magnetism 4. A greater degree of safety, leading to dif culty in damaging the data stored 5. Light weight 6. SSDs use controllers to read, and write data. There are three types of solid-state storage: Solid-state disks (SSDs): which are designed to be connected inside of microcomputer system the same way an internal hard disk would be, but the difference is contain slowed state memory, instead of magnetic disks to store data. Data is stored electronically and directly on Solid state memory (microchips).There disks are faster and require less power. They are used for tablet PCs like the iPad Flash Memory Cards: are Solid- state electronic data storage devices that are used with digital cameras, telephones, music players, video games, and other electronics. They can be moved from the camera and placed in a card reader that is connected to the computer or printer. USB Flash Drives: are compact and easy to use devices that are similar in use to your computer’s hard drive. USB ash drives nally ful ll the real promise of the digital age, which is complete freedom, and mobility. fl fi fi fi fi fi One way of data storage is: - Cloud Storage: is the where the Internet provides cloud storage which is also known as online storage.Cloud services provide storage, processing, and memory. you can retrieve data from the servers any time cloud servers are owned and managed by hosting companies such as Google, Microsoft, and Amazon. These hosting companies are responsible for keeping their data available and accessible. 2 SOFTWARE Computer software concept: Hardware can not work without programs. A program is a set of sequence instructions that tell the computer what to do. Software is a collection of programs. Hardware is built on physical equipment but Software is built on thinking, knowledge and planning. A programmer is the person who makes the program, using one of the computer’s programming languages. Types of software: 1. System Software: is the software which is used by the computer to handle computer technical tasks. For example, System Software controls where a word processing program is stored in memory. System software consists of four types of programs: Operating System: is the most important system software. It holds all the instructions that make the computer work, such as starting the computer, displaying on the monitor, using the keyboard, saving and loading les, using Secondary Memory, and managing the application software by being an interface between them and the computer’s equipment. Some of the operating systems are: Windows Linux Unix Macintosh Operating System (Mac OC). Android iOS (iPhone OS) Functions of operating systems: - Booting up - User Interface - Task and resources management - Monitoring - Files management - System security Utilities : are specialized programs designed to make computing easier. They include anti-virus programs, backup programs and le compression programs. Device Drivers: work with the operating systems to allow communications between the device and the rest of the computer system. Language Translators: are programs that translate the source code (high-level code) to object code (low-level or machine code). fi fi  2. Application Software: is used by users to perform certain tasks. Examples of application software include: Word Processing: Application, which are used for producing letters memos, etc. An example is MS-Word. Spreadsheet Applications (MS-Excel): which can be used to do budget, sales projections and nancial plans. Excel allows you to use formulas to display, analyze, and summarize data. Database Applications: which are used for organizing large amounts of information.An example is MS-Access Desktop publishing (DTP): which is used to mix texts and graphics, including photos, to produce a high-quality printed output used for Journal issuing. An example is Adobe Photoshop. Presentation Applications: which are used for producing pictures, advertisements, and manuals. An example is MS-PowerPoint Web Browsing: applications ( such as Internet Explorer and Google chrome) which are used for displaying Web pages from the Internet. E-Mail Software: which allows you to type a message, attach it to le stored on the disk, and send the message to one or more users at the same time, and forward it to other users. Examples are Outlook Express and Microsoft Outlook. Computer Games: are games played on personal computers. PC games are created by one or more game developers, and are then distributed on physical media such as DVDs and CDs or as Internet downloadable shareware. 3 DATA COMMUNICATION AND COMPUTER NETWORKS Data communication: is the process of sharing data, programs, and information between two or more computers. Examples of applications that depend on communication systems include: E- government, E-mail and E-commerce. Communication System: are electronic systems that transmit data from one location to another. Communication systems can be: wired or wireless and their basic elements are: Sending and Receiving Devices: from/to computer or a specialized communication device. Communication Channel: which carries the message and can be consist of a physical wire or be wireless. Connection Devices: which act as an interface between sending and receiving devices and convert outgoing messages into packets( key term) that can travel across the communication channel Data Transmission Speci cations: which are the rules and procedures that coordinate the sending and receiving devices. Transfer Rate: is the volume of data that can be traveled via a transmission media in one second and measured via several ways: Bps: is the number of bits transmitted in one second ( it is the slowest). Kbps: is the number of kilobits transmitted in one second. Mbps: is the number of megabits transmitted in one second. Gbps: is the number of gigabits transmitted in one second( it is the fastest). fi fi fi The speed of data transmission is affected by several factors, including: 1. Bandwidth: A bandwidth is a measurement of the width of capacity of the communication channel.It means how much information can move across the communication channel in a given amount of time. There are four types of bandwidth: Voiceband: which is also known as low bandwidth, is used for standard phone lines. It is too slow, and its typical speeds are 56 to 96 kbps. Medium band: which is used with special leased lines to connect minicomputers and mainframes as well as to transmit data over long distances. It is not typically used by individuals Broadband: which is used for high-speed, high-capacity and high-quality transmission. Baseband: which is widely used to connect individual computers that are located close to each other. It is slower than the broadband 2. Protocols: are a set of instructions and procedures that rule exchanging data between computers. Types of protocols include: HTTP(HyperText Transfer Protocol): is a protocol widely used for web traf c. It allows a text with links to be transmitted from one computer to another. HTTPS(HyperText Transfer Protocol Secure): is widely used to protect the transfer of sensitive information. Transmission Control Protocol/Internet Protocol (TCP/IP): is the standard protocol for the Internet. Every computer on the Internet has a unique numeric address called an IP address. The Internet uses the IP address to deliver e-mail and to locate Wep sites as these numeric addresses are dif cult for people to remember and use.The Domain Name Server (DNS) is a system used to convert a text address to a numeric IP address. When you send a message, it will be broken into small parts called Packets. At the receiving end, the packets are reassembled in the correct order. Digital and Analogue Signals: Many computer communications take place over telephone lines. However, because the telephone was originally designed for voice transmissions, telephones typically send and receive Analogue Signals, which are continuous electronic waves. computers, in contrast, send and receive Digital Signals Modem: modem ( short for modulate/demodulate) converts digital signals into an analog form( a process known as Modulation) to send over phone lines. A receiving modem at the other end of the phone line then converts the analog signal back to a digital signal (a process known as Demodulation). The speed with which modems transmit data varies. This speed is called the Transfer Speed, and is typically measured in Megabits per second (Mbps). The higher the speed is, the faster you can send and receive information. fi fi Types of Modems: 1. The telephone: where computers are linked to the phone. This technique is very slow compared to other techniques. 2. The DSL(Digital Subscriber Line): uses standard phone lines to create a high speed connect. ASDL( asymmetric digital subscriber line) is one of the most widely used types of DSL. 3. The Cable: which uses the same coaxial cable used by the television,creating a high speed connection. 4. The Wireless modem: which is also known as the WWAN modem, creates a high speed connection. Networks: Is a group of computers connected to each other to exchange information and to share resources such as printers ,peripheral equipment, les and programs. Some network necessary concepts: Node: is any device connected to a network. It could be a computer, printer or data storage device. Client: is a note that requests and uses resources from other nodes. Server: is a node that shares resources with other nodes. Depending on the tasks it performs, a server may be called an application server, a communication server, a database server , a le server or a Web server. The Network Interface Card (NAC): each computer that is part of the network must have a network interface card installed. This device creates a communication channel between the computer and the network. The Network Operating Systems (NOS): control, and coordinate the activities of all computers and other devices on a network. These activities include: electronic communication and the sharing of information and resources. Types of Networks: The Local Area Network (LAN): is the number of computers that are linked together by cables in a limited area(a building or a group of nearby buildings). For instance, if 10 people are working together within an of ce when connected to a network, they can share printers, modems, scanners and les. Wireless LAN (WLAN): is a network that links two or more computers or devices using wireless technologies, such as radio waves to enable communication between devices in a limited area. This gives users the mobility to move around within a board coverage area and still be connected to the network. Home Network: is similar to LANs and WLANs but works within a very small area, sharing resources include common Internet connections. Personal Area network (PAN): is a wireless network, which works within a very small area. For example, PANs connect PDAs two other PDAs, keyboards to sell phones, and so on. Metropolitan Area Network (MAN): spans distance up to 100 miles.MANs network links nodes and resources within the geographical bounds of a city. fi fi fi fi  Wide Area Network (WAN): computers and computer networks are linked together over a large area. Many WANs use satellite communications. WAN is used to connect of ces of an by organisation that are located in different cities in the same country or in different countries.Moreover, WAN is used to connect the Bank ATMs. The largest WAN is the Internet. Internet: is the largest global network. It’s a collection of linked computer networks. It uses standard protocols such as the (TCP/IP) protocol. The Internet was launched in1969. Intranet: Is a private network within an organisation used by the organisation’s employees. The intranet resembles the Internet and that it uses browsers, websites and web pages. Extranet: It’s also a private network, but it connects more than one organisation. It also allows suppliers and other limited access to the network. 4 IT & COMMUNICATIONS IN OUR EVERYDAY LIFE The Internet and web provide numerous resources and activities that can be used in our daily life. The following every everyday activities, often use computer applications and the Internet: E-Commerce: is buying and selling goods or services via the Internet. You can pay using Credit Cards. In this case, you need to enter your credit card details. You can also pay via by Digital cash. Which is preformed through a third-party( your bank, for example). This third party is responsible for the payment security. A famous Wep site for e-commerce is Amazon.com. You can browse the site and add any products to your shopping cart and then move to the checkout stage, where you should enter your name, address, time of delivery and payment details. The advantage of using e-commerce are as follows: Service available 24/7/365: Purchase can be made 24 hours a day and 7 days a week, making it available to every place in the world, at any time. Large stock range: the stock does not have to be distributed over many physical stores Detailed product information: you can compare between product of mini companies and then decide on the product you want. Ability to compare prices: you can compare between the product’s price on different sites. Equal Delivery: no matter where you live, you can get the product and save time as you can buy software and pay for it and then download it immediately. Right to Return Defective Goods: Most sites will have a Returns policy, and it is available to read this prior the purchase. Forms of e-commerce are: - Business to Consumer (B2C): describes activities of business between a company and individuals consumer directly. - Business to Business (B2B): this is a term commonly used to describe commerce transactions between business companies. fi - Consumer to Consumer (C2C): this is a term commonly used to describe commerce transactions between individuals. Individuals can set up their own webpages and take orders directly for goods and service.A common example, is the online auction in which a customer posts an item for sale and other customers bid to purchase it. To avoid problems when making online purchases, do the following: 1. Choose the (secure server) option when making purchases online. 2. Use a separate credit card with lower limit and use only that card for online purchases. 3. Do not share your credit card information with anyone 4. Avoid using your credit card to pay through sites with a bad reputation. 5. Check the feedback from others who have used the site if possible. E-Banking: Banks: use computers to enable customers to access their accounts via ATM machines. You can control your day today nances pay bills and move money between accounts from your home. The service is available 24 hours and it’s reduce the bank’s investment and staff and buildings. E-banking include the following: Telephone Banking: which allows customers to perform nancial transaction over a telephone that uses an automated phone answering system with a phone keypad response or voice recognition capability. Online Banking: which allows customers to conduct nancial transitions on a secure Wep site operated by there retail or bank. It offers features such as: bank statements, electronic bill payment, funds transfer, loan applications, and transitions. It also allows users to monitor all their accounts in one place. SMS Banking: which uses customers’ mobile phone with SMS to perform nancial transactions. The bank sends messages about updates on the customer’s account, such as a large withdrawal of funds from the ATM E- government: The performance of governmental institutes can be improved through the use of computers which can save, search for and sort a large amount of data. Examples on information that can be stored in a computer or data related to names, addresses and national numbers. When I knew transaction is performed, new details are added to the database. The data stored can be used in national records to perform marketing research as well as social and statistical surveys such as population statistic, funds collection, and others. Additionally, it can be used for registering vehicles through keeping a record for the persons who have a driving license and for every vehicle. E-learning: refers to learning through the Internet or through computers. Computers are used in registration and timetabling. There are many special programs designed to computeriz management tasks: Computer-Based Training (CBT): uses interactive programs and modern multimedia computers to enable people to acquire skills and knowledge in a way that may be more convenient, more practical and less expensive than traditional methods. The advantages of CBT are: 1. One trainer can train many people are different locations. 2. Student can work in their free time and repeat the course parts, which they don’t understand. 3. It’s more con dent, more practical and less expensive than traditional methods fi fi fi fi fi  The disadvantages of CBT are: 1. The learners do not have the bene t of interacting with each other 2. The Internet connection may fall for any reason 3. The downloading speed may be too slow 4. The material may not be available for sometime, following the release of a new version of software or adding a new syllabus Teleworking: One works at home and communicates with the of ce by a computer network. Advantages of teleworking are: 1. It saves time and money for the employee and reduce environmental pollution. It can help ease traf c and the stress resulting from it. 2. Its focus on one task, as there are no interruption from low priority phone calls, or from colleagues who want to chat or complain about the boss. 3. Flexibility of working hours. As long as the job gets down at doesn’t matter “when” it gets down Therefore, there will be time for other activities. 4. It’s reduce of ce desk space requirements. From anywhere the employee has access to the Internet or he or she can use his telephone device to get the task done.Hence there’s no need to move closer to the actual job site 5. The employer can hire employees from different regions Disadvantage of teleworking: 1. Self-discipline: at home, there are a lot of distractions that can be dif cult to get the work done if you have children phone calls, or guests. 2. Lack of Human Contact: you will not be working with workers, so you will not be able to develop the types of relationships that can help your network. You also may not have a lot of interaction with others. 3. Negative Impact on Teamwork: as you do not meet with the rest of the team, it’s hard to feel that you are part of the team Internet Telephones: (VoIP): which stands for voice over Internet protocol means hardware and software that enable people to use the Internet as the transmission medium for telephone calls by sending voice data in packets using IP(Internet protocol) rather than using traditional circuit transmission. Instant Messaging: is an online communication between two or more people who are connected to the Internet. Skype Service: provides audio and video service that do not require any dedicated hardware. Once you subscribe to this free service, you can use your computer’s existing audio and video devices to connect to any (online) Skype subscribers fi fi fi fi fi  5 PRIVACY AND SECURITY Viruses: Are software programs which are written with the intention of causing inconvenience and disruption or serious damage in a computer system. Files can spread the viruses cause a network or via e-mail and the Internet. Types of viruses : 1. Worms viruses: spread by replicating themselves. They don’t make any damage, but they spread very quickly and networks and keep computer systems busy wasting vast amount of computers time. 2. Time Bombs: which cause the damage at a speci c time. 3. Boot-Sector: is that part of the system software containing most of the instructions for booting or powering up the system. The boot sector virus replaces these boot instructions with some others of its own. Then the system never starts up. 4. File Viruses: attach themselves to executable les( les, having the extensions.com and.exe). When the program is run, the virus starts working, trying to get into the main memory, and infects other les. 5. Macre Viruses: our computer viruses that use and application’s own macro programming language to distribute themselves. Opening an MS-word document, or a template that contains a macro virus will infect your system and the virus will spread to other decrements and templates you may have on your system. 6. Trojan Horse: covertly places illegal distractive instruction in the middle of a legitimate program, such as a computer game. Once you run the program the Trojan horse starts to work causing damage while you are unaware. How can viruses enter a computer system? Viruses hide on disks. when you access the disk the virus will, infect you computer.It then can spread from one computer to another. When you connect to the Internet, you have to make sure that Antivirus programs are working and are updated. Protection Against Viruses: Some of the indicators that your computer might be infected are the following: When it runs slower than normal When it crashes and restarts every few minutes When it restarts on its own, and then fails to run normally When applications it do not work correctly When you see unusual error messages and then disks or disk drives are inaccessible To protect your computer from viruses use high-quality anti-virus programs such as: Norton Kasper Sky McAfee And be sure to updated regularly. Use it to scan any les, program ,software or diskettes (even new software from a commercial company) before you use them on your computer. ‫ال تنسوني من دعواتكم‬ ‫شهد الغامدي‬ fi fi fi fi fi