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Study Unit 4 COMPUTER SYSTEMS AND DATA COMMUNICATION Introduction Computerised information systems use hardware and software to generate information. This information must then be communicated to the user by using specific communication methods. In this study unit, we look at information systems, accounting information systems and modern methods of communication. Communication Theory Communication is the transfer of information from a sender to a receiver. It refers to the means and methods whereby data is transferred between processing locations through the use of communication systems. Communication systems are defined as systems for creating, delivering and receiving electronic messages. The communication system comprises of the following A device to send the message The channel or communication media A device to receive the message An information system is a system that comprises people, machines and methods by which data is collected, processed, transferred and distributed. The system may be manual or automatic. This study unit will focus on the automatic system. An accounting information system measures business activities (data), processes the data and communicates usable information to decision makers. What is a Network? Before the evolution of networks, organisations made use of stand-alone computer systems. Computers would be found in strategic places in the organisation but were not linked to each other. Stand-alone computers are now used mainly by sole proprietors and for personal use. Computer networks are now more accessible to organisations and individuals on a large scale. Terminals are linked to a mainframe and this gives users access to a central processing function. These terminals can be linked via internal or external communication channels. A network consists of two or more computers that are linked in order to share resources, such as printers and CD-ROMs, exchange files, or allow electronic communications. There are different configurations that can be used to ensure connectivity. Configuration refers to the way that hardware devices are connected to each other. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams. Fig 4.1 gives an example of a network in an organisation comprising a local area network or LAN connecting computers with each other, the Internet, and various servers. The three basic types of networks include: Local Area Network (LAN) Wide Area Network (WAN) Metropolitan Area Network (MAN) Local Area Network The Local Area Network (LAN) enables multiple users in a relatively small geographical area to exchange files and messages, as well as access shared resources such as file servers. Rarely are LAN computers more than a mile apart. It is generally limited to a geographic area such as a writing lab, school, or building. 2 In a typical LAN configuration, one computer is designated as the file server. It stores all of the software that controls the network, as well as the software that can be shared by the computers attached to the network. Computers connected to the file server are called workstations. The workstations can be less powerful than the file server, and they may have additional software on their hard drives. On most LANs, cables are used to connect the network interface cards in each computer. Wide Area Network The Wide Area Network (WAN) is an interconnection of various LANs through telephone network to unit geographically distributed users. Dedicated transoceanic cabling or satellite uplinks may be used to connect this type of network. Using a WAN, anybody in Zimbabwe can communicate with countries like Japan in a matter of minutes, without paying enormous phone bills. For example when we log on to the Internet, we become a part of a WAN. A WAN uses special communication tools such as multiplexers to connect local and metropolitan networks to global communications networks like the Internet. To users, however, a WAN will not appear to be much different than a LAN or a MAN. Metropolitan Area Network The Metropolitan Area Network (MAN) is usually the interconnection between various LANs in a particular geographical area like a metropolitan city like Harare. Computer Networks configurations Basically, there are two types of network configuration, peer-to-peer networks and client/server networks. A network is referred to as peer-to-peer if most computers are similar and run workstation operating systems. Peer-to-peer networks are more commonly implemented where less then ten computers are involved and where strict security is not necessary. All computers have the same status, hence the term 'peer', and they communicate with each other on an equal footing. Files, such as word processing or spreadsheet documents, can be shared across the network and all computers on the network can share devices, such as printers or scanners, which are connected to any one computer. Other computers can access these resources but a computer that has a particular resource must be turned on for other 3 computers to access the resource it has. For example, if a printer is connected to computer A and computer B wants to print to that printer, computer A must be turned on. A computer network is referred to as client/server if (at least) one of the computers is used to "serve" other computers referred to as "clients". Besides the computers, other types of devices can be part of the network. Client/server networks are more suitable for larger networks. A central computer, or 'server', acts as the storage location for files and applications shared on the network. Usually the server is a higher than average performance computer. The server also controls the network access of the other computers which are referred to as the 'client' computers. Typically, teachers and students in a school will use the client computers for their work and only the network administrator (usually a designated staff member) will have access rights to the server. In a client/server environment, each computer still holds (or can still hold) its (or some) resources and files. Other computers can also access the resources stored in a computer, as in a peer-to-peer scenario. One of the particularities of a client/server network is that the files and resources are centralized. This means that a computer, the server, can hold them and other computers can access them. Since the server is always On, the client machines can access the files and resources without caring whether a certain computer is On. Another big advantage of a client/server network is that security is created, managed, and can highly get enforced. To access the network, a person, called a user must provide some credentials, including a username and a password. If the credentials are not valid, the user can be prevented from accessing the network. The client/server type of network also provides many other advantages such as centralized backup, Intranet capability, Internet monitoring, etc. Table 4.1 provides a summary comparison between Peer-to-Peer and Client/Server Networks. Table 1: Peer-to-Peer Networks vs Client/Server Networks Peer-to-Peer Networks vs Client/Server Networks Peer-to-Peer Networks Easy to set up Less expensive to install Client/Server Networks More difficult to set up More expensive to install A variety of operating systems can be supported on the client computers, but the server needs to run an operating system that supports networking Can be implemented on a wide range of operating systems 4 More time consuming to maintain the software being used (as computers must be managed individually) Less time consuming to maintain the software being used (as most of the maintenance is managed from the server) Very low levels of security are supported or none at all. These can be very cumbersome to set up, depending on the operating system being used High levels of security are supported, all of which are controlled from the server. Such measures prevent the deletion of essential system files or the changing of settings Ideal for networks with less than 10 computers No limit to the number of computers that can be supported by the network Requires a server running a server operating system Does not require a server Demands that the network administrator has a high level of IT skills with a good working knowledge of a server operating system Demands a moderate level of skill to administer the network Why Network Computers? The primary purpose of a computer network is to share resources. Computers networks allow people to share information, software, and any resources, including hardware, more efficiently. For example: You can play a CD music from one computer while sitting on another computer You may have a computer with a CD writer or a backup system but the other computer doesn’t have it; In this case, you can burn CDs or make backups on a computer that has one of these but using data from a computer that doesn’t have a CD writer or a backup system You may have a computer that doesn’t have a DVD player. In this case, you can place a movie DVD on the computer that has a DVD player, and then view the movie on a computer that lacks a DVD player You can connect a printer (or a scanner, or a fax machine) to one computer and let other computers of the network print (or scan, or fax) to that printer (or scanner, or fax machine) You can place a CD with pictures on one computer and let other computers access those pictures You can create files and store them in one computer, then access those files from the other computer(s) connected to it 5 Components of a Network In order to set up a computer network relevant network hardware and software are required. Network hardware Networking hardware includes all computers, peripherals, interface cards and other equipment needed to perform data-processing and communications within the network. This section provides information on the following components: File Servers Workstations Network Interface Cards Switches Repeaters Bridges Routers File Server A File server is a high capacity computer that provides various resources to the network. It is the heart of a network and must have the following things: need a very fast computer with a large amount of RAM and storage space, a fast network interface card, and a tape back-up device need network operating system such as Novell Netware, Windows NT server, or Apple Share control the communication of information between the nodes on a network If you plan to use one of your existing computers as the server, check its hardware and make sure it meets the following requirements: A processor with 133-MHz or higher speed; 550-MHz recommended; up to eight processors supported on one server 128 MB of RAM minimum required; 256 MB or more recommended; 32 GB maximum 1.25 to 2 GB of available hard disk space CD-ROM or DVD-ROM drive VGA or hardware that supports console redirection required; Super VGA supporting 800 x 600 or higher-resolution monitor recommended 6 Workstations A computer in a network is called a workstation or client. This computer needs a network interface card to enable it to be connected to the network backbone. It does not necessarily need floppy disk drives or hard disks since files can be saved on the file server. When you are planning to use a computer as a workstation as a network, you should make sure that computer meets the necessary requirements. In some cases, it may only meet the hardware requirements without any software. In some cases, something could be missing. If you decide to purchase brand new computers, as a reminder of what we reviewed in chapter one, here are the hardware requirements the computer must meet: A processor with 300 megahertz or higher processor clock speed recommended; 233 MHz minimum required (single or dual processor system); Intel Pentium/Celeron family, or AMD K6/Athlon/Duron family, or compatible processor recommended 128 megabytes (MB) of RAM or higher recommended (64 MB minimum supported; may limit performance and some features) 1.5 gigabytes (GB) of available hard disk space Super VGA (800 x 600) or higher-resolution video adapter and monitor CD-ROM or DVD drive Keyboard Microsoft Mouse or compatible pointing device Network Interface Cards (NICs) A network interface card (NIC) which is pronounced 'nick', is also known as a network card. It connects the computer to the cabling, which in turn links all of the computers on the network together. Each computer on a network must have a network card. The three common network interface connections are Ethernet cards, LocalTalk connectors, Token Ring cards. Most modern network cards are 10/100 NICs and can operate at either 10Mbps or 100Mbps Only NICs supporting a minimum of 100Mbps should be used in new installations schools. Most of these are internal, with the card fitting into an expansion slot inside the computer and some build on the motherboard. 7 Fig 5: Network Interface Cards (NICs) We mentioned that a network card could also be used or installed externally. This can be done using USB. Here is another example: Hubs/Concentrators A hub is a device used to connect multiple devices, including PC, printers, and scanners, to the network. It serves as a central meeting place for cables from computers, servers and peripherals. To make this possible, a hub is equipped with small holes called ports. They usually have 4, 8, 12, or 24 RJ-45 ports. The entire network shuts down if there is a problem on a hub. Here are some examples of commonly found hubs. Fig 6a: An 8 port Hub Fig 6b: 2 Examples of 24 port Switches When configuring a hub, you connect an RJ-45 cable from the network card of a computer to one port of the hub. 8 The function of a hub is to direct information around the network, facilitating communication between all connected devices. However in new installations switches should be used instead of hubs as they are more effective and provide better performance. Switches Switches are the more recent technology and the accepted way of building today's networks. They are essentially high-speed multi-port bridges which are more efficient than with any other type of hub. With switching, each connection gets "dedicated bandwidth" and can operate at full speed. As a result, a switch is often termed a 'smart hub'. In contrast, a hub shares bandwidth across multiple connections such that activity from one PC or server can slow down the effective speed of other connections on the hub. Now more affordable than ever, Dual-speed 10/100 autosensing switches are recommended for all school networks. Schools may want to consider upgrading any hub based networks with switches to improve network performance, that is, the speed of data on the network. Repeaters A repeater is a device that regenerates and amplifies signals to create longdistance networks. They simply receive, amplify and rebroadcast the signals although some repeaters can provide basic error-checking. They are used to overcome distance limitations. Repeaters can be separate devices or they can be incorporated into a concentrator. Bridges A bridge is a device that links two homogenous packet-broadcast local networks. A bridge is used to connect two or more networks using the same address method or protocol. It is often used when LANs reach their capacity of nodes. It accepts all packets from each network addressed to devices on the other, buffers them, and retransmits them to the other network. It also monitors and manages the traffic to maintain optimum performance on both sides of the network. Routers Like a hub, a router is another type of device that acts as the central point among computers and other devices that are part of a network. Here is an example of a wired router. 9 Routers are similar to bridges in that they link two or more physically separate network segments. The network segments linked by a router, however, remain logically separate and can function as independent networks. A router functions a little differently than a hub. In fact, a router can be considered a little "intelligent" than the hub. Like a hub, the computers and other devices are connected to a router using network cables. To make this possible, a router is equipped with holes, called ports, in the back. Here is an example. Network Operating System A network operating system is a supervisory software program that resides on the server. It controls how the network operates by defining who can use the network and how information and peripherals are shared among users. The most commonly used network operating systems in schools are from the Microsoft windows family, which include Windows NT, Windows 2000 Server. Novel Netware, UNIX, LYNX and others are not common in our schools. Network Media Network Cables Cable is the medium through which information usually moves from one network device to another. There are several types of cables which are commonly used with LANs. In some cases, a network will utilize only one type of cable, other networks will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. You need to understand the characteristics of different types of cables and how they relate to other aspects of a network in order for you to develop a successful network. In this section we discuss the following types of cables used in networks: Unshielded Twisted Pair (UTP) Cable 10 Shielded Twisted Pair (STP) Cable Coaxial Cable Fiber Optic Cable Wireless LANs The two most popular types of structured network cabling are twisted-pair (also known as 10BaseT) and thin coax (also known as 10Base2). Unshielded Twisted Pair (UTP) Cable Twisted pair cabling comes in two varieties: shielded and unshielded. Unshielded twisted pair (UTP) is the most popular and is generally the best option for school networks (See fig. 1). This cable looks like ordinary telephone wire, except that it has 8 wires inside instead of 4. It consists of two insulated copper wires arranged in a regular spiral pattern to minimize the electromagnetic interference between adjacent pairs. It is a low frequency transmission medium. This cable is the most popular and is generally the best option for school networks, because of its low cost and easy installation. It is also ideal for short distance, usually less than 100 meters. Fig 4a: Cat5e Cable and a close up of RJ-45 connector Fig 4c: Cat5e Patch Panel Fig 4b: Cat5e Wall Outlets 11 Fig4d: Wall Mounted Cabinet Categories of Unshielded Twisted Pair Type Category 1 Category 2 Category 3 Category 4 Category 5 Use Voice Only (Telephone Wire) Data to 4 Mbps (LocalTalk) Data to 10 Mbps (Ethernet) Data to 20 Mbps (16 Mbps Token Ring) Data to 100 Mbps (Fast Ethernet) 10BaseT cabling is available in different grades or categories. Some grades, or "cats", are required for Fast Ethernet networks, while others are perfectly acceptable for standard 10Mbps networks--and less expensive, too. All new networks use a minimum of standard unshielded twisted-pair (UTP) Category 5e 10BaseT cabling because it offers a performance advantage over lower grades. The standard connector for UPT cable is an RJ-45 connector, which looks like a large telephone modular connector Coaxial (Coax) Cable Thin coax looks like the copper coaxial cabling that's often used to connect a Video Recorder to a TV. It has an inner conductor surrounded by a braided mesh. Both conductors share a common center axial, hence the term "co-axial". It can support a size of 12 bandwidth of up to 400 Mhz and can be used for distances between 300 and 600 meters. Its major advantage is that it is highly resistant to signal interference. Its major disadvantage is that it is quite bulky and sometimes difficult to install. The most common type of connector used with coaxial cables is the BNC (Bayone-Neill-Concelman) connector, which is shown in fig …. below. There are two types of coaxial cable namely thin coaxial which is also referred to as thinnet and thick coaxial which is also referred to as thicknet . The 10Base2 is the IEEE standard for Ethernet running on thin coaxial cable. The 2 refers to the approximate maximum segment length being 200 meters. This is popular in school networks, especially linear bus networks. The IEEE standard for Ethernet running on thick coaxial cable is 10Base5. The 5 refers to the approximate maximum segment length being 500 meters. Thicknet has an extra protective plastic cover that helps keep moisture away from the center conductor. Its major disadvantage is that it is difficult to bend and install. Fibre Optic Fibre optics consists of a center glass core surrounded by several layers of protective materials. Fibre optic’s major advantage is that it is immune to environmental interference and has a greater capacity (bandwidth of up to 2 Gbps) It is used for distances up to 100 kilometers and carries information at vastly greater speeds. It is also very small and lighter in weight than other media. Its major limitation is that it is very expensive. It is difficulty to install, hence requires highly skilled installers and modifiers. Even with highly skilled personal adding additional nodes is difficult. Network media access methods How computing devices access the network cable and send data is known as the media access method. There are four commonly used media access methods: Ethernet, Token Ring, Local Talk, and FDDI. 13 Ethernet Ethernet is the most popular media access method which can allow for linear bus, star, or tree topologies. It use access method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection). It is able to transmit data over UTP, thincoaxial, thick-coaxial and fiber optic cables at rates of 10 Mbps. Fast Ethernet supports 100 Mbps, but requires faster hubs and network interface cards Token Ring Token ring was developed by IBM in the mid 1980s. It uses a star-wired ring topology over shielded and unshielded twisted-pair wiring. A central hub (referred to as a "MAU" Multi-station Access Unit) is at the center of the ring. There are two versions of Token Ring, namely 4 Mbps and 16 Mbps. They both use a token passing process to circulate packets around the ring. These are more expensive than Ethernet, but are a good option for PC networks. Local Talk Local talk was developed by Apple Computer, Inc. for Macintosh computers and is best suited to small networks of Macs. It allows for linear bus, star, or tree topologies using twisted pair cable and can connect up to 32 devices (computers, printers, and file server). Local talk uses the CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) process for transmitting data. A single network can be up to 300 meters. Its major disadvantage is that it is slow, transmits data at only 230 Kbps. FDDI (Fiber Distributed Data Interface) FDDI uses fiber optics for speeds of up to 100 Mbps. The system is used primarily to interconnect two or more LANs, often over long distances. It employs the token ring passing process to transmit data; but use a dual counterrotating ring topology, meaning there are two rings of cable with two tokens circulating in opposite directions. Wireless Not all networks are connected with cabling; some networks are wireless. The term 'wireless network' refers to two or more computers communicating using standard network rules or protocols, but without the use of cabling to connect the computers together. Wireless LANs use high frequency radio signals, infrared light beams, or lasers to communicate between the workstations and the file server or hubs. Each workstation and file server on a wireless network has some sort of transceiver/antenna to send and receive the data. Information is relayed between transceivers as if they were physically connected. For longer distance, wireless communications can also take place through cellular telephone technology, microwave transmission, or by satellite. 14 Fig 7b: Desktop PC Wireless LAN card Fig 7c: Laptop PC Wireless LAN card A wireless local area network (WLAN) consists of two key components: an access point (also called a base station) and a wireless card. Information can be transmitted between these two components as long as they are fairly close together (up to 100 metres indoors or 350 metres outdoors). The types of infrared communications that we could use in schools are line-of-sight and scattered broadcast. Line-of-sight communication means that there must be an unblocked direct line between the workstation and the transceiver. If a person walks within the line-of-sight while there is a transmission, the information would need to be sent again. This kind of obstruction can slow down the wireless network. Scattered infrared communication is a broadcast of infrared transmissions sent out in multiple directions that bounces off walls and ceilings until it eventually hits the receiver. Networking communications with laser are virtually the same as line-of-sight infrared networks. Wireless LANs have several disadvantages. They provide poor security, and are susceptible to interference from lights and electronic devices. They are also slower than LANs using cabling. Advantages of a Wireless LAN Wireless LANs have advantages and disadvantages when compared with wired LANs. A wireless LAN will make it simple to add or move workstations, and to install access points to provide connectivity in areas where it is difficult to lay cable. Temporary or semi-permanent buildings that are in range of an access point can be wirelessly connected to a LAN to give these buildings connectivity. Where computer labs are used in schools, the computers (laptops) could be put on a mobile cart and wheeled from classroom to classroom, providing they are in range of access points. Wired network points would be needed for each of the access points. The installation of cables is time consuming and expensive. The advantages of not doing so are apparent: the amount of work required and the time taken to complete it are significantly reduced the network is accessible in places where wiring would have been difficult or impossible 15 with no cables linking computers together, cable-related faults and network downtime are minimised Where a wireless network is in place, teachers or students can have continuous access to the network, even as they move with their equipment from class to class. The space over which a wireless network operates is not planar but spherical. Therefore, in a multi-level site, network access is available in rooms above or below the access point, without the need for additional infrastructure. In a location within a school where network access is required occasionally, desktop computers fitted with wireless network cards can be placed on trolleys and moved from location to location. They can also be located in areas where group work is taking place. As they are connected to the network, documents and files can be shared, and access to the Internet is available, enhancing group project work. As the range of the wireless network extends outside the building, students and teachers can use wireless devices to gather and record data outside, e.g., as part of a science experiment or individual performance data as part of a PE class. Below are some specific advantages of a WLAN: It is easier to add or move workstations It is easier to provide connectivity in areas where it is difficult to lay cable Installation can be fast and easy and can eliminate the need to pull cable through walls and ceilings Access to the network can be from anywhere in the school within range of an access point Portable or semi-permanent buildings can be connected using a wireless LAN Where laptops are used, the ‘computer suite’ can be moved from classroom to classroom on mobile carts While the initial investment required for wireless LAN hardware can be similar to the cost of wired LAN hardware, installation expenses can be significantly lower Where a school is located on more than one site (such as on two sides of a road), it is possible with directional antennae, to avoid digging trenches under roads to connect the sites In historic buildings where traditional cabling would compromise the façade, a wireless LAN can avoid drilling holes in walls Long-term cost benefits can be found in dynamic environments requiring frequent moves and changes They allows the possibility of individual pupil allocation of wireless devices that move around the school with the pupil. 16 Disadvantages of a WLAN As the number of computers using the network increases, the data transfer rate to each computer will decrease accordingly As standards change, it may be necessary to replace wireless cards and/or access points Lower wireless bandwidth means some applications such as video streaming will be more effective on a wired LAN Security is more difficult to guarantee, and requires configuration Devices will only operate at a limited distance from an access point, with the distance determined by the standard used and buildings and other obstacles between the access point and the user A wired LAN is most likely to be required to provide a backbone to the wireless LAN; a wireless LAN should be a supplement to a wired LAN and not a complete solution Long-term cost benefits are harder to achieve in static environments that require few moves and changes It is easier to make a wired network ‘future proof’ for high data transfer. Network Topologies Networks have a physical and a logical topology. In this section the physical topology of a network is discussed. The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations. Main Types of Physical Topologies The physical topologies that are commonly found in computer networks are: Linear Bus Star Star-Wired Ring Tree Considerations When Choosing a Topology Summary Chart Linear Bus (Trunkline) A linear bus topology consists of a main run of cable with a terminator at each end (See fig. 4.1). All nodes (file server, workstations, and peripherals) are connected to the linear cable. 17 It is easy to connect a node to a linear bus and less expensive since network structure requires less cable. Its major disadvantage is that the entire network shuts down if there is a break in the main cable and it is difficult to identify the problem if the entire network shuts down. Advantages of a Linear Bus Topology Easy to connect a computer or peripheral to a linear bus. Requires less cable length than a star topology. Disadvantages of a Linear Bus Topology Entire network shuts down if there is a break in the main cable. Terminators are required at both ends of the backbone cable. Difficult to identify the problem if the entire network shuts down. Not meant to be used as a stand-alone solution in a large building. Star A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub or concentrator (See fig. 5.2). A separate cable connects to each computer, and if one cable breaks, only a single computer should be affected. The hub or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. Data on a star network passes through the hub or concentrator before continuing to its destination. The hub or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable. Advantages of a Star Topology Easy to install and wire. No disruptions to the network then connecting or removing devices. Easy to detect faults and to remove parts. 18 Disadvantages of a Star Topology Requires more cable length than a linear topology. If the hub or concentrator fails, nodes attached are disabled. Star Wired Ring (Token Ring) Star wired ring (Token ring) network was developed by IBM for IBM-compatible computers. It employs a special coded message called a token that the operating software passes in sequence to each computer on the network. It has a bandwidth capacity of 4 or 16 Mbps using twisted pair cables. Daisy-Chain The Daisy-Chain network is similar to a bus, except the electrical signal is routed through each computer as it moves along the line. Thus it is not practical in multiroom network installations. It is mainly used on the Macintosh network. Its major advantage is that it is easy to install. The entire network shuts down if there is a problem on a node. The Daisy-Chain network is very slow. 19 Wireless Network Configurations Wireless networks can be configured in an ad hoc/peer-to-peer arrangement or as a local area network. Ad Hoc/Peer-to-Peer Configuration This is the most basic wireless network configuration. It relies on the wireless network adapters installed in the computers that are communicating with each other. A computer within range of the transmitting computer can connect to it. However, if a number of computers are networked in this way, they must remain within range of each other. Even though this configuration has no real administration overhead, it should only be a consideration for very small installations. The Internet What is the Internet? The Internet which is also known as the Net is simply a network of networks. It is a world wide computer network that interconnects computer networks across countries. A network is a group of computers that are connected so that they can share information. The computers are linked together through high speed telephone wires, satellite and any other telecommunication system such as cable networks. All computers on the Internet communicate with one another using the Transmission Control Protocol/Internet Protocol suite, which is commonly abbreviated to TCP/IP. As a network of networks, the Internet allows people on one network to share information with people on another network that may be thousands of miles away. Through the Internet, one has access to a wide variety of services which include : vast information resources, interactive collaboration tools, multimedia displays, real-time broadcasting, shopping opportunities, and much more. These services are available through the: World Wide Web, electronic mail (email), file-transfer between any two computers and, remote access to a computer connected to the Internet. 20 What is needed to connect to the Internet The minimum set of requirements to connect to the Internet is: a computer attached to an Internet entry point (a service provider) via a telecommunication link such as the telephone line and a modem. These are discussed in detail below. Internet Service Providers An Internet Service Provider (ISP) is a company that gives you access to the Internet. In Zimbabwe the common ISPs are ComOne, ZARNet, AfricaOnline, Ecoweb, ZOL , PowerTEL and many others. You sign up for an Internet access account through your selected ISP. Once you sign up for a dial-up account with an ISP, you will be able to communicate through the Internet and use the services offered, such as email and Internet access. Your ISPs can also provide you with numerous other Internet related services, such as domain name registration and website hosting. Modem When you are connecting through a telephone link, a modem is required. The modem must be connected to a telephone line to dial up your ISP’s computer network. A modem (MODulator - DEModulator) is a device that translates digital (numerical) signals from your computer into analogue signal (sounds) that are acceptable for an ordinary telephone line. A modem could be internal, that is, attached on the computer’s motherboard or connected external through a communication port on your computer. To connect to the Internet using a dial-up connection you need a modem with a speed of 56 Kbps modems, which is the maximum for an ordinary telephone line. The speed at which data circulates through the modem and the telephone line is called bandwidth. The first modems had very low bandwidth of 300 to 1200 bit per second (bps). Today, even 14.4 Kbps (kilobit per second) and 28.8 Kbps modems have become obsolete. 21 Telecommunication link A telecommunication link such as the telephone, satellite, fibre optics is required for connecting to the Internet. For a dial-up connection, a telephone link is required. When you dial to link your computer to the ISP network, your computer is connected to the Internet. As with ISP, your telephone services provider will offer many different plans and charging systems from flat rates to blocks of time. You must find the plan that works best for you according to prices that are offered and your specific needs. It is always better to connect to the Internet on a direct telephone line through an automatic connection system because the quality of the line is very important. However, some technical solutions can correct mistakes and remove noise and disturbances. When the Internet entry point is in your local area, you will not need to pay for an intercity or trunk call, but for a local call. In Zimbabwe we dial 041 as the local call to connect to the Internet. This Internet connection will provide you with access to the entire world through your local connection. Please note that you are responsible for paying the telephone bill for the time you will be connected to the Internet. Other types of telephone connection are dedicated lines, and the Integrated Services Digital Network (ISDN) Dedicated lines A dedicated line is a telecommunication path between two points that is available 24 hours a day for use by a designated user. A dedicated line is rented from a telephone company, in which case it is called a leased line. Thus unlike dial-up lines, it is not shared in common among multiple users. In this type of connection, you will pay the agreed rate to ISP, but you do not pay additional costs for the time spent while surfing the Internet. Such lines are ideal for schools and colleges where the Internet is need throughout the day. Integrated Services Digital Network (ISDN) Using an Integrated Services Digital Network (ISDN) adapter, instead of a conventional modem allows the transmission of data on an ordinary telephone wire at a much higher speed. When you connect using an ISDN adapter in place of a modem, you can access highly graphic webpages with easy and at a fast speed of up to 128 Kbps. This new technology is not readly available in many developing countries. Since ISDN requires adapters at both ends of the transmission, your access provider also needs an ISDN adapter. So before you make the decision to install an ISDN adaptor you must check if your ISP has one. In some countries, ISDN is available from phone companies in urban areas. 22 The web browser In addition to the things listed above, there are a number of pieces of software that works together to connect us to the Internet. One such software is the Internet browser. The browser helps us to locate websites and allows us to maneuver around or surf the World Wide Web as we view web pages. The two most frequently used graphic browsers are Microsoft's Internet Explorer, and America Online (AOL)'s Netscape Navigator. Before these graphic browsers were in use, Mosaic and Lynx were the most popular browser and these are still available for text browsing. Internet Services On the Internet we have access to a wide variety of services. In this section were are going to discuss, a few of these services, namely, the World Wide Web (WWW), electronic mail (e-mail), file transfer protocol (FTP) and UseNet news. Electronic Mail Electronic mail (e-mail) refers to the sending of digitally encoded messages through the network. Electronic mail is one of the fastest and easiest ways of sending electronic messages from one person to another or to a group. Email systems enable us to conveniently and quickly send a message to many people at one time. Messages sent through e-mail can arrive within a matter of seconds. Although email is used primarily for sending written messages, we can also send and receive pictures, sounds and video images as attachments to the text message. These files are referred to as MIME attachments. MIME stands for Multimedia Internet Mail Extension. This technique was developed to help e-mail software handle a variety of file types. For example, a document created in Microsoft Word can be attached to an e-mail message and retrieved by the recipient with the appropriate e-mail program. They are basically two types of e-mail accounts, these are, the one we can be given by our Internet Service Provider (ISP) and the one we can get free from the Internet. The email account we can obtain from the ISP is some times called the computer-based account. Computer based accounts have the advantage that students can downloads all their messages to read and respond to them offline. That is when they are not connected to the Internet. Students can only connect to download or post their messages. This saves on the telephone bill if the connection is a dial-up connection. The Internet based email account is sometimes known as web-based account. Web based email accounts are usually free of charge and they are available from a number of providers on the Internet. These include yahoo mail, Hotmail, Gmail and many others. The major advantage of web-based mail is that students can easily gain access from any computer with Internet access. The World Wide Web 23 The World Wide Word (WWW) or simply the Web is another commonly used Internet service. The World Wide Web is a system of Internet servers that supports hypertext to access several Internet protocols on a single interface. It provides Internet users with a uniform and convenient means of accessing a wide variety of resources including pictures, text, sound and video, available on the Internet. It provides a vast array of experiences including multimedia presentations, real-time collaboration, interactive pages, radio and television broadcasts. Both the teacher and the learner can retrieve documents, view images, animations and videos, listen to sound files, speak and hear voices through the Web. The information is found on files called web pages or web sites. A web site is a set of interlinked files on a web server computer. Each website has an address, known as a “URL,” that locates it on the internet. Websites are typically organized around a “home page” that serves as the entry point to other pages. Websites can present information in words, pictures and sounds, and they can enable us to exchange information with our students. A web page is written in a special programming language called hypertext mark up language (HTML) and its filename ends with file extension html. Hypertext is basically a document containing words that connect to other documents. The principle of hypertext is that one text or web page can refer to or point to another web page, either on the same website or another website somewhere else in the world. Thus it is easy for the web pages to link to another web page on the same computer or different computers, anywhere on the Internet. The pages are linked by special links called a hyperlinks. The hyperlink can be taken as a method of instant cross-referencing of information on web. A hyperlink is shown by a coloured and underlined stretch of text or graphic image where the shape of the cursor changes to a pointing hand. These words are called links and are selectable by the user. In some cases hyperlinks take the form of buttons, images, or portions of images that are clickable. A single hypertext document can contain links to many documents. When you select one of these words or phrases, you will be transferred to the site or page that is linked by the word or phrase. How to Access the World Wide Web For you to access the World Wide Web a Web browser is required. A browser is a software program that allows users to access and navigate the World Wide Web. There are two types of browsers, namely graphical and text browsers. These are explained in detail below. Text Browsers Text browsers, such as Lynx provide access to the Web in text-only mode. Navigation is accomplished by highlighting emphasized words on the screen with the up and down arrow keys, and then pressing the forward arrow or the Enter key 24 to follow the link. Today, these browsers are fast loosing their popularity due to the development of more user friendly graphical browsers. Graphical Browsers A graphical browser such as Internet explorer, Netscape Navigator, Mozilla and opera, enable us to retrieve text, images, audio and video. These browsers are available for Windows, Apple, Linux and other operating systems. Navigation is accomplished by pointing and clicking with a mouse on highlighted words and graphics. Browser buttons Address bar Back Forward Home Refresh Stop Scroll bar Homepage Location on the browser where one enters addresses to web sites. The address bar is usually located on the top of the screen and it written “address.” Clicking this button brings you back to a previous screen. The back button is located in the upper left hand corner of the screen. Clicking on the “Forward” button brings you to a page that you viewed earlier Clicking on “Home” on the top of the screen brings you to the home location to which the computer is set. Computers can be and are set to open to different Web site addresses. Clicking on “Refresh” reloads an expired page or a page that has timed out. Clicking this button stops the computer from loading a new page. The vertical gray space on the right and the horizontal gray space on bottom of the browser screen allows you to view parts of a Web page that do not fit inside the screen. When you cannot see the entire Web page, use the small box or the small arrows to move the page up and down, left and right. Refers to the beginning page of a Web site. This page will link to other information found within the Web site as well as outside of the Web site. A Note on Clicking Clicking Double clicking Drop down menu Link Use one quick (left) mouse click to open up a link or to darken (highlight) the address bar to type in a new web address. Use two quick (left) mouse clicks to open up a program on your screen (such as Microsoft Word, Internet Explorer, etc.). Programs are usually represented by symbols known as icons. Clicking on a drop down menu reveals links. These menus are recognized by a small downward pointing arrow Links are found on nearly all Web sites and take you from one part of the Web site to another (usually referred to as another “page”). Links can also take you to a completely different Web site. Links may be text (often underlined and colored blue) or a picture. When using a mouse, the arrow becomes a hand when it is placed over a link. 25 Telnet Telnet is one of the services available on the Internet. Telnet allows the user to log onto computers on the Internet and use online databases, library catalogs, chat services, and more. The major disadvantage of Telnet is that there are no graphics in Telnet sessions. The most common Internet based resources available through Telnet are library catalogs, although most catalogs are now migrating to the Web. As the Web gains more popularity, Telnet is less frequently used as a means of access to information on the Internet, thus why most library catalogues are now migrating to the web. A Telnet program must be installed on your local computer and configured to your Web browser in order to work. To Telnet to a computer, you must know its address. The addresses may consist of words (msu.ac.zw) or numbers (10.10.1.8). File Transfer Protocol (FTP) FTP stands for File Transfer Protocol. This is both a program and a method used to transfer files between computers. FTP is used primarily as a tool to efficiently uploading and downloading files on the Internet. FTP sites contain books, articles, software, games, images, sounds, multimedia and many other forms of information. FTP transfers can also be performed on the World Wide Web without the need for special software. Programs such as WS_FTP for Windows can be used to conduct a file transfer. FTP files can also be retrieved via search engines such as FtpFind, with URL http://www.ftpfind.com. This option is easiest because one does not need to know FTP program commands. The Web browser is sufficient to carry out the process. In fact every time we download software from a Web site to our computer, we will be using FTP. 26 StudyUnit 5 THE ROLE OF INFORMATION AND COMMUNICATION TECHNOLOGIES IN BUSINESS Introduction Businesses rely on information because it allows them to make decisions. Incorrect decisions can be fatal and reliable information is therefore of critical importance. The output of information systems consists of information, which is made available to users who then base their decisions on it .This study unit will look at: Who these users are And why these users need the information that they need END USERS OF INFORMATION External users Internal users TYPES OF INFORMATION SYSTEMS Transaction processing systems Management information systems Decision support systems Executive information systems Expert information systems USES OF INFORMATION SYSTEMS They help an organisation to maintain an advantage over its competitors by offering new services to clients before competitors can and by improving the cost and quality of existing services. IMPACT OF INFORMATION AND COMMUNICATION TECHNOLOGIES Increasing use of the internet, e-mail, and e-commerce Has also led to the development of new legislations to govern the use and conduct of users of these technologies In the work environment , computers have led to the following 27 Reduced need to follow chain of command Information overload Retraining of staff Closer business relationships Working from home Human computer interface Effects of technology on the workforce OPPORTUNITIES, ADVANTAGES AND RISKS OF USING COMPUTERS IN BUSINESS Information technologies have allowed people around the globe to be able to trade with each other any time of the day and year. Business opportunities are now unlimited but they bring with them new risks and threats. FURTHER STUDY Read from ISSABE, Chapter 28 8 (para 8.5.5) 29 Study unit Study Unit 6 1 THE MANAGEMENT OF INFORMATION SYSTEMS Introduction Because of the rapid developments in the field of information technology, it must be managed effectively. Management should be carefully plan hoe to handle the information systems. Such a plan is called a strategy. An organisation that does not have an information systems strategy is like a rowing boat adrift a big ocean. The information strategy Information systems are critical for the success of many organisations and hence the need to have a well organised information management system in place. This need also stems from the following: The high costs involved in acquiring and maintaining information systems The increased levels of customer service due to the use of information systems The achievement of competitive advantage The improved quality of information that can impact on the quality of decisions taken by management. 30 The formulation of an information systems Plan Strategic analysis using critical success factors This involves analysis of small numbers of key and vital goals that are vital for the success of an organisation. SWOT Analysis An organisation must analyse its internal environment 31 Study unit 7 DEVELOPING NEW INFORMATION SYSTEMS Introduction This study unit presents an overview of the main stages involved in the development of information systems. There are a number of ways by which an information system can be developed. The choice of a particular method depends on the specific characteristics of the development project such as The size Scope Limitations Time scale And the user’s specifications One of the more popular methods is the systems development life cycle (SDLC).This model is based on a logical step-by-step approach to system development There are other strategies that an organisation could use if it doesn’t want to develop the new system on its own. These will be discussed later in the study unit as well. Reasons why systems get obsolete or become outdated 1. The rapidly changing technological environment 2. Changing output needs of the information system The Systems Development Life Cycle 32 The phrase “systems development” covers the development of computer systems from the initial idea through to the eventual installation of working systems The development of particular system is carried out by a project team which will consist of: Users Managers Data processing staff consisting of systems analysts, programmers and database analysts All projects to develop information systems go through a number of stages known collectively as the Systems Development Life Cycle (SDLC).The SDLC is an example of a systems development methodology. A methodology is simply a collection of stages, procedures and techniques to assist systems developers in the construction of new information systems. It is the segmenting of projects which allows managers to verify the successful completion of project phases before allocating resources to subsequent phases. A disadvantage of this model is that it does not guarantee the optimal use of human resources, because each stage deends on the successful completion of the previous stage.It alsdo focuses primarily on project organisation, rather than meeting the users’ needs. The stages in the SDLC and their respective end products are: 1. Project Definition The result is statement of scope and objectives 2. Feasibility study Result is the Feasibility report 3. Systems Analysis Result is a detailed requirements specifications report 4. Systems Design Result is Systems specification 5. Programming Result is a Program specifications and Program code 6. Implementation Result is a live system 33 FURTHER STUDY What is involved at each stage of the SDLC Why it is important to involve the user during each stage of the SDLC ALTERNATIVE WAYS OF DEVELOPING OR ACQUIRING INFORMATION SYSTEMS There are disadvantages in using structured system analysis and design methods when developing information systems and for this reason one may choose to use alternative methods. The information system does not to be developed by the organisation itself. Please read ISSABE, Chapter 10 ( Para 10.4) paying particular attention to the following: Off the shelf software packages Prototyping (modelling) Application development tools Software houses/ bureaus End-user development Outsourcing Re-engineering of business processes Joint applications development Rapid applications development 34 Study unit 8 Information System Controls Introduction An organisation’s protection of its information-based assets is now seen as an important and real challenge. The violation of privacy and the illegal use of information systems to commit crime or to bring about economic loss to a third party have a number of legal and financial implications. Most common threats that exist include: Errors of omission at data input/entry Fraud by theft Disgruntled employees Physical and infrastructure threats Malicious hackers Industrial espionage Unauthorised and inappropriate use of information systems Employee lack of know-how on use of information technologies. 35 COMPUTER CRIME Computer crime includes criminal activities of a traditional nature, such as theft, fraud, forgery and mischief. In summary the types of Computer Crimes are: Fraud by computer manipulation Computer forgery Damage to or manifestation of computer data or programs Unauthorised access to computer systems and services Unauthorised reproduction of legally protected computer programs. Introduction of malicious programmes/ viruses Computer hacking DATA SECURITY This refers to measures that are meant to reduce unauthorised access to, use and destruction of an organisation’s data and data resources. Threats to security come from outside (external) and inside (internal) the organisation. Securing data entails making sure that the computers are in the right environment, there are right software measures to reduce loss or theft of data. Security of Equipment This entails the need to look after the computer hardware well to avoid loss of data or the computers themselves. These include 36 Ventilation A good room has to be adequately ventilated. If ventilation is poor the computer may over heat and thus fail to operate properly. Power supply Should be of the right voltage and supplied from safe socket outlets Use of Uninterrupted Power Supplies (UPS) Carpet These are good dust absorbers. Fust interferes with the operation of electronic equipment. Curtains They reduce the amount of light an heat getting to the computer screens. Lockable doors Metal bars and shutters This reduces unauthorised access An alarm system This may help warn of an intrusion ID badges They limit access to the room to authorised individuals only Security guards Attach computers permanently to the desks using clamps to avoid theft of the computers Have all equipment serial numbers for use if equipment is stolen. Have fire fighting systems in place to deal with any risks of fire to the equipment. 37 Security of Data Data itself is at risk of accidental or deliberate loss and theft. Accidental loss may occur this way Document may be accidentally deleted Computer breaks down or power fails File or disk becomes corrupted File is is destroyed by fire or flood To reduce the risk of loss there is the use of back-up of data. Best way to keep backups is to make sure that a copy is kept on a different medium and in a different place. Deliberate damage is loss of data by viruses or hackers. Computer Virus A virus is a harmful program that copies itself onto other programs and destroys them or interferes with their proper functioning. To reduce the risk of virus infections, the following may be effective: Use anti-virus software Use genuine software Write protect all software programs Make regular back-ups 38 CONTROLS A security policy should clearly state what controls need to be implanted to limit computer crime. This policy should be revised regularly to determine whether the organisation’s confidentiality and integrity are still protected. Controls are usually categorized as: Preventative These are designed to prevent unauthorised or invalid data entries Detective These help to identify unauthorised or invalid entries Corrective These assist in recovering from unwanted occurrences Typical control mechanisms that maybe included in such a policy are: APPLICATION CONTROLS and CONTROL STANDARDS Application controls include policies and procedures associated with user activities and the automated controls designed into applications. Application controls are categorized as follows: Input controls These help ensure employees accurately input information, systems properly record input, and systems either reject or accept and record, input errors for later review and correction. Database and file controls 39 Processing controls They help ensure systems accurately process and record information and either reject, or process and record, errors for later review and correction. Processing includes merging files, modifying data, updating master files and performing file maintenance. Output controls They help ensure that systems securely maintain and properly distribute processed information. Controls should be in place to address both batch and on-line environments. Standards should address procedures to ensure management appropriately approves and control overrides. OPERATIONAL CONTROLS and STANDARDS Please read ISSABE Chapter 11 ( Para 11.4- 11.4.3.2.4) 40