MAJMA'AH UNIVERSITY. Introduction to Computer

Transcription

1 MAJMA'AH UNIVERSITY Introduction to Computer 1

2 What are computers? Computers are electronic devices that accepts input or data from users, and then process it and then produce information. data processing information 2

3 computer components HARDWARE SOFTWARE 3

4 Hardware The parts of computer itself hardware including the Central Processing Unit (CPU) and, case,ram,rom,drives (hard, CD, DVD, floppy,,, etc...). Other extra parts called peripheral components or devices include keyboard, monitor,mouse, printers, modems, scanners, digital cameras etc... Together they are often referred to as a personal computer. 4

5 Hardware The parts of computer itself include : Input devices i.e. the keyboard and mouse Output devices i.e. monitor, printer CPU (or Processor) Memory (Main or Primary Memory & Secondary or Auxiliary Memory) Storage devices i.e. hard disk,flash memory others 5

6 6 Hardware

7 The Case (System Unit or System Cabinet) 7

8 Components of a Computer System Data Central Processing Unit (CPU) control unit (CU) Input units Arithmetic logic Unit (ALU) Memory ROM RAM output units 8 Auxiliary Memory Information /Knowledge

9 Input Devices... Hardware Organization CPU memory motherboard hard drive 9

10 Input Devices Input devices consists of external devices - that is, devices outside of the computer's - that provide data and instructions to the computer Translate data from form that humans understand to one that the computer can work with it Most common are keyboard and mouse Selector Buttons 10

11 Examples of Input Devices 1. Keyboard - The keyboard is used to type data into the computer or input data. There are many different keyboard layouts and sizes ex. ( ATMs keyboard) ATM: automatic teller machine The standard keyboard has 101 keys. Some of the keys have a special use. There are referred to as command keys. The 3 most common are the Control or CTRL, Alternate or Alt and the Shift keys though there can be more (the Windows key for example or the Command key). Each key on a standard keyboard has one or two characters. Press the key to get the lower character and hold Shift to get the upper 11

12 Examples of Input Devices 2. Mouse Most modern computers today are run using a mouse controlled pointer. Generally if the mouse has two buttons the left one is used to select objects and text and the right one is used to access menus. If the mouse has one button (Mac for instance) it controls all the activity and a mouse with a third button can be used by specific software programs. 12

13 Examples of Input Devices One type of mouse has a round ball under the bottom of the mouse. Laptop computers use touch pads, buttons and other devices to control the pointer Handhelds use a combination of devices to control the pointer, including touch screens. 13

14 Examples of Input Devices 3. Scanner Scanners allow you to transfer pictures and photographs to your computer. A scanner 'scans' the image from the top to the bottom 4. Pre-storage Devise (Disk, CD s, etc.) 5. Microphone 14

15 Examples of Input Devices(2) 6. Point and Draw devices 7. Touchpad 8. Touch screen 9. Magnetic stripes and smart cards. 10. Digital Cameras 15

16 Hardware Organization CPU memory hard drive 16 Output

17 CPU Output Devices Pieces of equipment that translate the processed information from the CPU into a form that humans can understand. 17

18 Examples of output devices: Screen (Monitor) Printer Speaker Etc. Output Devices 18

19 Monitors Output Devices Monitor - A monitor is the screen on which words, numbers, and graphics can be seem. The monitor is the most common output device. It s the most important output device 2 common types CRT (Cathode Ray Tube ) LCD (Liquid Crystal Display) 19

20 Output Devices Printers - A printer prints whatever is on the monitor onto paper. Printers can print words, numbers, or pictures. A computer printer, or more commonly just a printer, is a device that produces a hard copy of documents stored in computer form, usually on physical print media such as paper 20

21 Output Devices Printers kinds Dot matrix printers Ink jet printers Laser printers 21

22 Output Devices Printers kinds 1- Dot matrix printers A dot matrix printer or impact matrix printer refers to a type of computer printer with a print head that runs back and forth on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a typewriter. Unlike a typewriter, graphics can be produced. 22

23 Output Devices Printers kinds 2- Ink jet printers Ink jet printers are a type of computer printer that operates by propelling tiny droplets of liquid ink onto paper. They are the most common type of computer printer for the general consumer due to their low cost, high quality of output, capability of printing in vivid color, and ease of use. 23

24 Output Devices Printers kinds 3- Laser Printers Laser printers are that uses laser technology to print images on the paper. These work in a manner similar to a photocopier. The laser recreates the image on a negatively drum. A roller is charged with electricity, then a laser is used to remove the charge from portions of the roller. Powdered ink (toner) sticks to the parts of the roller that were hit by the laser, and this toner is transferred from the roller to the paper. Then the ink is baked into the paper using a heater. 24

25 Output Devices Speaker A speaker gives you sound output from your computer. Some speakers are built into the computer and some are separate. Speakers allows the computer to display sound. 25

26 Mother-Board (or Main Board) CPU RAM ROM 26

27 Mother-Board (or Main Board) The Main Printed Circuit Board Inside The PC That Contains and Controls The Components That Are Responsible For Processing Data. Motherboard Holds : The Processor Memory Expansion Slots Connects Directly or Indirectly to Every Part of The PC 27

28 Hardware Organization CPU memory motherboard hard drive 28

29 Central Processing Unit (CPU) A specific chip or the processor 29 a CPU's performance is determined by the rest of the computers circuitry and chips. The Central Processing Unit (CPU) performs the actual processing of data The speed of CPU measured by Hertz (MHz)

30 The CPU consists of : Control Unit (CU) Arithmetic and Logical Unit (ALU) Some Registers 30

31 The Control Unit (CU) : coordinates all activities of the computer by: Determining which operations to perform and in what order to carry them out. The CU transmits coordinating control signals to other computer components. 31

32 The ALU : consists of electronic circuitry to perform: Arithmetic operations (addition (+), subtraction (-), multiplication (*) and division (/) Logical operations (and, or, not, ) and to make some comparisons (less-than (<=)equal (=), etc.) 32

33 Others : Case - The case houses of the microchips and circuitry that run the computer. They come in many sizes There is usually room inside to expand or add components at a later time. By removing the cover off the case you may find plate covered, empty slots that allow you to add cards. There are various types of slots including IDE, ASI, USB, PCI and Fire wire slots. 33

34 Modem - A modem is used to translate information transferred through telephone lines, cable or line-of-site wireless. The term stands for modulate and demodulate which changes the signal from digital, which computers use, to analog, which telephones use and then back again. Digital modems transfer digital information directly without changing to analog. 34

35 35 Modems are measured by the speed that the information is transferred. The measuring tool is called the baud rate. Originally modems worked at speeds below 2400 baud but today analog speeds of 56,000 are standard. Cable, wireless or digital subscriber lines (DSL) can transfer information much faster with rates of 300,000 baud and up.

36 36 Anyone who has used the Internet has noticed that at times the information travels at different speeds. Depending on the amount of information that is being transferred, the information will arrive at it's destination at different times. The amount of information that can travel through a line is limited. This limit is called bandwidth

37 Others Cards - Cards are components added to computers to increase their capability. When adding a peripheral device make sure that your computer has a slot of the type needed by the device Sound cards Network cards etc 37

38 Others Cables connect internal components to the Motherboard, which is a board with series of electronic path ways and connections allowing the CPU to communicate with the other components of the computer. 38

39 Others Drives : CD ROM Drive Floppy Disk Drive DVD Drive (Digital Video Disc) 39

40 40 Kinds of Disk Drives

41 Memory We may be put memory in two sections: Main or Primary Memory Secondary or Auxiliary Memory But now will use the term of memory (or main memory) in two general parts: 1.RAM 2.ROM And we will use term storage devices to Secondary or Auxiliary Memory 41

42 RAM (Main Memory) The main memory in a computer is called Random Access Memory. It is also known as RAM. This is the part of the computer that stores operating system software, software applications and other information for the central processing unit (CPU) to have fast and direct access when needed to perform tasks. It is called "random access" because the CPU can go directly to any section of main memory, and does not have go about the process in a sequential order. 42

43 RAM (Main Memory) it temporarily holds data and programs for use during processing (volatile) Any information stored in RAM is lost when the computer is turned off. RAM is the memory that the computer uses to temporarily store the information as it is being processed. The more information being processed the more RAM the computer needs. RAM consists of locations or cells. Each cell has a unique address which distinguishes it from other cells. RAM memory chips come in many different sizes and speeds and can usually be expanded. 43

44 Older computers came with 512 Kb of memory which could be expanded to a maximum of 640 Kb. In most modern computers the memory can be expanded by adding or replacing the memory chips depending on the processor you have and the type of memory your computer uses. Memory chips range in size from 1 Mb to 4 Gb. As computer technology changes the type of memory changes as well making old memory chips obsolete. Check your computer manual to find out what kind of memory your computer uses before purchasing new memory chips. 44

45 RAM is one of the faster types of memory, and has the capacity to allow data to be read and written. When the computer is shut down, all of the content held in RAM is purged. Main memory is available in two types: Dynamic Random Access Memory (DRAM) and Static Random Access Memory (SRAM). 45

46 DRAM Dynamic random access memory (DRAM) is the most common kind of main memory in a computer. It is a prevalent memory source in PCs, as well as workstations. Dynamic random access memory is constantly restoring whatever information is being held in memory. It refreshes the data by sending millions of pulses per second to the memory storage cell. 46

47 SRAM Static Random Access Memory (SRAM) is the second type of main memory in a computer. It is commonly used as a source of memory in embedded devices. Data held in SRAM does not have to be continually refreshed; information in this main memory remains as a "static image" until it is overwritten or is deleted when the power is switched off. Since SRAM is less dense and more power-efficient when it is not in use; therefore, it is a better choice than DRAM for certain uses like memory caches located in CPUs. Conversely, DRAM's density makes it a better choice for main memory. 47

48 48 Main Memory

49 ROM: Read Only Memory ROM is part of memory Programmed at manufacturing time Its contents cannot be changed by users It is a permanent store Q: Mention some examples of ROM? A: (PROM & EPROM ) 49

50 Other Kind of Memory PROM: Programmable Read Only Memory. EPROM: Erasable Programmable Read Only Memory Cache Memory Registers: not part of the main memory. Q : Registers are part of? 50

51 Storage Devices Stores data and programs permanently: its retained after the power is turned off Discs are used to store information. All information on computers are stored in files. The size of a file is measured in bytes. A byte is approximately one character (letter 'a', number '1', symbol '?' etc...). 51

52 Storage Devices byte is made up of 8 bits. A bit is simply an on or an off signal which passes through the computers circuitry. Every piece of software can be broken down into a series of on or off signals or it's Binary Code. About a thousand bytes is a kilobyte (Kb). About a million bytes is a megabyte (Mb). About a billion bytes is a gigabyte (Gb). About a trillion bytes is a terabyte (Tb) Note: I say 'about' because everything in computers must be divisible by 8 so a kilobyte is actually 1,024 bytes. The reason for this goes beyond the scope of an introductory level document but as it can cause some confusion I thought it should be mentioned 52

53 Units of Measurements Bit (Binary Digit)(takes two values: 1 or 0) Byte = 8 bits KB (Kilobyte) = 1024 bytes MB (megabyte) = 1024 KB GB (gigabyte) = 1024 MB TB (Terabyte) = 1024 GB 53

54 Storage Devices Disc are a common way of transporting information such as bringing files home from work or sharing files. Floppy disks have become less useful as file sizes increase and Compact disks (CDs), Flash drives and Digital Video Devices (DVDs) are becoming more popular. Most software is sold on a CD. Internal Hard disks are the most common storage device. 54

55 Storage Devices Compact disks or CDs can store large amounts of information. One disk will store 650 Mb. One type is a CD-ROM which stand for Compact Disk Read Only Memory. Another type is a CD-RW which stands for Compact Disk - Read/Write. CD drives can copy information or burn information on to a blank CD. Common Read Only CD blanks can only be written to once though more expensive Read/Write CD's can be used over and over again. 55

56 Storage Devices Hard disks store the majority of information on today's modern computer. Some of the first hard disk stored 10 to 40 Mb. Today the standard hard disk stores 150 Gb or more (this number is constantly increasing). Information can be stored and deleted as necessary. As files get larger the speed that hard disks can read and write become more important 56

57 Storage Devices Hard Drive (Hard Disk) Located outside the CPU, but most often contained in the system cabinet Data is represented magnetically as with diskettes These disks are not removable Significantly more capacity and faster operating than diskettes 57

58 Common Secondary Media Diskettes Data represented as magnetic spots on removable flexible plastic disks Most common size is 3 1/2 inches, in a rigid plastic case Disk drive holds the diskette, reads or retrieves the data and writes or stores data 58

59 Common Secondary Media Disk size Amount of storage Approximate printed 8.5 x 11 inch pages 5.25 low density 3.5 low density 5.25 high density 3.5 high density CD DVD 360 Kb 720 Kb 1.2 Mb 1.44 Mb 700 MB 8.5 GB 180 pages 360 pages 600 pages 720 pages a small library a feature length movie 59

60 Common Secondary Media tapes Panasonic's LS inch diskettes Iomega's Zip & Jazz disks VCR tape (Video Cassette Recorder ) Flash USB disks MMC (Multi Media Card ) 60

61 61 The benefits of secondary storage can be summarized as follows: Capacity. Organizations may store the equivalent of a roomful of data on sets of disks that take up less space than a breadbox. A simple diskette for a personal computer holds the equivalent of 500 printed pages, or one book. An optical disk can hold the equivalent of approximately 400 books. Reliability. Data in secondary storage is basically safe, since secondary storage is physically reliable. Also, it is more difficult for unscrupulous people to tamper with data on disk than data stored on paper in a file cabinet.

62 62 Convenience. With the help of a computer, authorized people can locate and access data quickly. Cost. Together the three previous benefits indicate significant savings in storage costs. It is less expensive to store data on tape or disk (the principal means of secondary storage) than to buy and house filing cabinets. Data that is reliable and safe is less expensive to maintain than data subject to errors. But the greatest savings can be found in the speed and convenience of filing and retrieving data.

63 Four Kinds of Computers 1. Microcomputers 2. Minicomputers 3. Mainframe computers 4. Supercomputers 63

64 Comparison between the previous kinds of computers may made based on : Price Processing Speed Storage Capacity Powerful Single-user or Multi-user Supporting hundreds (or thousands) of users simultaneously Computer Size Companies size etc. 64

65 Microcomputer =>Personal Computer => PC There are 3 types of the Microcomputers : 1.Laptop 2.Desktop 3.Workstation 65

66 Personal Computer: A small, single-user computer based on a microprocessor. Workstation: A powerful, single-user computer. A workstation is like a personal computer, but it has : a more powerful microprocessor and, in general, a higher-quality monitor. 66

67 Minicomputer, Mainframe, and Supercomputer Minicomputer: A multi-user computer capable of supporting up to hundreds of users simultaneously. Mainframe: A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously. Supercomputer: An extremely fast computer that can perform hundreds of millions of instructions per second. 67

68 Desktop Computer Small enough for a desktop, but not easily portable Personal computers (PC s) run general purpose software and are employed by a wide spectrum of users 68

69 Desktop Computers Cont. Workstations are powerful machines, running more advanced software, for technical, scientific, or dataintensive tasks These distinctions, however, are blurring 69

70 Portable Computers Easily transported from one place to another 70

71 Portable Computers Four categories 1. Laptops 2. Notebooks 3. Sub-notebooks 4. Personal Digital Assistants (PDA) 71 Q: list all portable computer categories?

72 72 PDA

73 73

74 Minicomputers Desk-sized More processing speed and storage capacity than microcomputers General data processing needs at small companies Larger companies use them for specific purposes 74

75 75

76 Mainframe Computers Larger machines with special wiring and environmental controls Faster processing and greater storage than minicomputers Typical machine in large organizations 76

77 Supercomputers The most powerful of the four categories Used by very large organizations, particularly for very math-intensive types of tasks 77

78 78 Supercomputers

79 Characteristics of Computers 1- Store a large amount of data and information for a long period of time. 2- process data and information in high accuracy level. 3- Speed in processing data information Sharing of information / network.

80 Understanding the difference between Data, Information and Knowledge: Data Computer Information Knowledge 80

81 Data: is the name given to basic facts such as names and numbers. Information: is data that has been converted into a more useful or intelligible form. Knowledge: arrangement of information and classifying information of the same type or the same topic. 81

82 Data Data: are details of various types of transactions and details relating to specific situations, which are input to a data processing system (e.g. computer) for processing in a prescribed way. Examples of data relating to students are studentnumber, student-name and grades. 82

83 e. g (data) sort \ / (information) 83

84 Data Document files Worksheet files Database files 84

85 Information Information: the result of processing data. Information: Must serve a useful purpose Must be of an acceptable level of accuracy Must be available at the right time Must be relevant to the enterprise, person, etc. Knowledge Putting a number of information with the same type or same topic would be a knowledge. 85

86 Generation of Computers The history of computer development is often referred to in reference to the different generations of computing devices. Each generation of computers is characterized by major technological development that fundamentally changed the way computers operate 86

87 Generation of Computers First Generation : Vacuum Tubes The first computers used vacuum tubes for circuitry and magnetic drums for memory, and were often enormous, taking up entire rooms Second Generation : Transistors 87 Transistors replaced vacuum tubes and ushered in the second generation computer. Transistor is a device composed of semiconductor material that amplifies a signal or opens or closes a circuit

88 Generation of Computers Third Generation : Integrated Circuits The development of the integrated circuit was the hallmark of the third generation of computers. Transistors were miniaturized and placed on silicon chips, called semiconductors, which drastically increased the speed and efficiency of computers. 88

89 Generation of Computers Fourth Generation Present: Microprocessors The microprocessor brought the fourth generation of computers, as thousands of integrated circuits we rebuilt onto a single silicon chip. A silicon chip that contains a CPU. In the world of personal computers,the terms microprocessor and CPU are used interchangeably. At the heart of all personal computers and most workstations sits a microprocessor. Microprocessors also control the logic of almost all digital devices, from clock radios to fuel-injection systems for automobiles 89

90 Generation of Computers Fifth Generation - Present and Beyond: Artificial Intelligence Fifth generation computing devices, based on artificial intelligence, are still in development, though there are some applications, such as voice recognition, that are being used today. 90

91 Software The instructions that tell the computer what to do Application Software - helps end-users perform general purpose tasks System Software - enables application software to interact with the computer The software that controls everything that happens in a computer. 91

92 System Software The most important System Software is the : Operating Systems Programs or applications software Programming languages

93 Examples of Operating System Software DOS - original standard for IBM compatibles Windows - a graphical operating environment Windows7, VISTA, XP, millennium,nt 2000, 98, and 95 93

94 Examples Operating System Software Windows NT - for powerful workstations & networks Macintosh Operating System Unix - originally for minicomputers, now used on microcomputers and Internet servers Question: List some examples of operating systems? 94

95 Application Software Packaged Custom Packaged - off the shelf, pre-written programs ( General purpose) Custom - written for an organization s specific purpose (Special purpose) 95

96 Application Software Basic Tools Word processors example: Microsoft word Spreadsheets-- example: Microsoft Excel Database managers-- example: Microsoft Access Graphics-- example: Photoshop 96

97 programming languages are : Low level languages example : machine language Assembly languages High level languages example : C,C++,JAVA,etc 97

98 Computer Viruses A computer virus is an application program designed and written to destroy other programs. It has the ability to: Link itself to other programs Copy itself (it looks as if it repeats itself) Example of viruses : Monkes,ABC,Crabs 98

99 Viruses and Virus Protection A virus program Infects programs, documents, databases and more It is man-made It can hide and reproduce It can lay dormant (inactive) and then activate Anti-virus programs can help 99

100 Viruses and Virus Protection (2) A variety of highly contagious viruses can spread from computer to computer, much the way biological viruses do among human beings. Just as a virus can infect human organs, a computer virus can infect programs and databases. It can also hide duplicates of itself within legitimate programs. 100

101 Viruses and Virus Protection(3) These viruses, which are programs, reside on and are passed between magnetic disks. Most people who write and circulate virus programs fall into two groups. 1. The first group uses viruses to show off for their peers. 2. The second, and far more dangerous group, creates viruses with malicious intent. 101

102 Types of Computer Viruses Macro viruses Written into the program macro Shuts down functions Worm A program that makes copies of itself It will interfere with normal operations 102

103 Sources of Computer Viruses Three primary sources The Internet Via downloads and exchanges Diskettes Exchanging disks Computer networks Can spread from one network to another 103

104 How do you know if you have a virus? Lack of storage capability Decrease in the speed of executing programs Unexpected error messages Halting the system 104

105 Virus Protection The software package distributed with new PCs always includes an antiviral program. The best way to cope with viruses is to recognize their existence and use an antiviral, or antivirus program. 105

106 Some tips that will help minimize your vulnerability to viruses: 1. Delete s from unknown or suspicious, untrustworthy (unreliable) sources, especially those with files attached to an Never open a file attached to an unless you know what it is, even if it appears to come from a friend. 3. Download files from the Internet only from legitimate and reputable sources. 4. Update your antivirus software at least every two weeks as over 200 viruses are discovered each month. 5. Backup your files periodically 6. Traditionally virus protection has been at the PC or client level. However, this may change as companies look to network and Internet service providers for more services. 106

107 Network What is a Network? A network consists of two or more computers that are linked in order to share resources (such as printers and files), exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams. 107

108 Network The three basic types of networks include: Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN) 108

109 Network Local Area Network A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a lab, school, or building. Rarely are LAN computers more than a mile apart. 109

110 Network Metropolitan Area Network A Metropolitan Area Network (MAN) covers larger geographic areas, such as cities or school districts. By interconnecting smaller networks within a large geographic area, information is easily disseminated throughout the network. Local libraries and government agencies often use a MAN to connect to citizens and private industries. 110

111 Network Wide Area Network Wide Area Networks (WANs) connect larger geographic areas, such as bank branches in KSA, or the world. Dedicated trans-oceanic cabling or satellite may be used to connect this type of network. 111

112 Internet What is the Internet? The Internet is a communication system that allows computers around the world to communicate and to exchange of the data with each other. 112

113 Internet The short history of the Internet It's in the 60's, in the middle of the "cold war" between the east block and the western countries, that one finds the starting point of the Internet. The American army needed a way to coordinate their nuclear weapons in case of atomic war. They needed a system of communication that could "survive" even if several bases were destroyed. 113

114 Internet The short history of the Internet 1964: ARPANET project: The beginning of the project to create the first distributed network. The advantage of this technology is that it's decentralized. The system is not dependent on a main computer to coordinate communications. If one, two, even several computers go out of order, are overloaded or are unavailable, the system can bypass these problems without any difficulty. This is the kind of network the military needed. 114

115 Internet The short history of the Internet : The ARPANET is put in operation with the use of a protocol for communications called NCP (Network Control Protocol). It's the first time computers communicate among each other over long distances. The whole network is composed of super-powerful computers for the period. The network could even survive the devastation of an atomic war because every site is physically connected to four others. The communication and the coordination of the surviving armed forces in a nuclear attack was and still is assured. For reasons of national security, the armed forces refuses scientists the access to the military network and the use of the protocol of communication between sites.

116 Internet The short history of the Internet 1973: The scientists take their revenge by developing their own network through universities and by using an improved protocol of communication named TCP / IP (Transfer Control Protocol Protocol/Internet Protocol). The protocol IP makes sure that every computer connected with the network has an unique address and that each is capable of communicating with the others. This protocol is used on several platforms to allow a communication from these. The access became, in time, international. The foundations for the current Internet ware placed. Research started to increase the potential of the Internet with several other services. 116

117 Internet The short history of the Internet Among these services, there is a . It allows people to send messages, " ", to each other who have an address. There is also " gopher " who allows to show data, mostly text, and to make it available to all. It's in a sense the "grandpa" of the World Wide Web. There is also a FTP service, for File Transfer Protocol, which allow the transfer of files through the Internet to FTP servers. There are several other services that will be described in this section of the site. 117

118 Internet The short history of the Internet 1995: It's this year when the term "Internet" entered the vocabulary of most people. It's especially because of a "new" service: the World Wide Web (WWW or W3). Some people think, even today, that the WWW is the Internet. By now 118

119 Internet The services of the Internet The Internet offers you several services. The main services are explained in the following. I can not give you a complete list of services because some people invent news ways to use the Internet every day! The potential of the Internet increases constantly. 119

120 Internet The services of the Internet Send and receive messages to other people that also have an address. Newsgroups Leave messages on the equivalent of " community board " on subjects that interests you. You can return later to see if you had answers to your comments or questions. Internet Relay Chat ( IRC) Communicate in real time with the other people who share your interests. 120

121 Internet The services of the Internet FTP or File Transfer Protocol Transfer files to or from FTP servers. Used to transfer files on Web sites or to get some files from servers. Telnet Allows to enter and to manage an account on a server. Telephony on the Internet 121 This is to have conversations by the voice on the Internet. Because of the configuration of the Internet, the parts of the message does not arrive in time and is not so agreed by the receiver. It's the equivalent of interurban without paying the expenses of it. To pay you only the costs of subscription of the service of access to the Internet.

122 Internet The services of the Internet Video Conference The video conference is the communication from the users by using of the video and the sound. With a small specialized video camera and a special program of communication, you connect to a server who takes charge of the communication between two or several persons. 122

123 Other terms Intranet Internet The use of tools and necessary resources to work on the Internet but for the internal needs of the company. For example, more and more companies use internal documents (memos, company reports and policies...) by using the same tools as on the Internet. However, these documents are only available from inside the company. 123

124 Other terms Extranet Internet It's the former term to describe what is now called Business to Business or B2B. This consists in the purchase of services and materials by transactions on the Internet between companies. 124

125 Other terms IP Address Internet Every computer connected to the Internet at an address IP (Internet Protocol). Like a postal address or a telephone number, it's used to know that computer made a query for data and to pass it on the correct place. So forget the anonymity on the Internet. It doesn't really exist. Your IP address is always used, always know. Act accordingly. 125

126 Other terms IP Address 126. Internet This address consists, at present, of a series of four figures between 0 and 255 ( 256 possibilities). All the addresses you will find so between and That gives you more than 4,2 billions addresses. The addresses are assigned in segments, or blocks, of 256 addresses to Internet service providers (ISP). It's they that assign an address to its users.