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CIBM BUSINESSINFORMATION SYSTEMSChapter Seven- Networking and Tele-Communications
7.1 LINKING UP: NETWORKBASICS A computer network is any computer system that links together two or more computers. The reason networking is important revolves around the three essential components of every computer system: Hardware. Networks allow people to share computer hardware, reducing costs and making it possible for more people to take advantage of powerful computer equipment. Software. Networks allow people to share data and software programs, increasing efficiency and productivity. People. Networks allow people to work together in ways that are otherwise difficult or impossible.
7.1.1 BASIC NETWORK ANATOMY A network extends the range of computer electrical pulses, allowing them to travel to other computers. A computer may have a direct connection to a network or it might have remote access to a network through a phone line and a dial-up connection. The Network Interface Personal computers communicate through serial ports with other computers. IBM- compatible PCs require a network interface card (NIC) containing the necessary serial port.
COMMUNICATION À LA MODEM The telephone network is ideal for connecting remote computers, too, except it was designed to carry sound waves, not streams of bits. Before a digital signal—a stream of bits—can be transmitted over a standard phone line, it must be converted to an analog signal—a continuous wave. At the receiving end, the analog signal first must be converted back into the bits representing the original digital message. Each of these tasks is performed by a modem (short for modulator/demodulator)—a hardware device that connects a computer’s serial port to a telephone line. A modem converts a computer’s digital signals into analog signals. The analog waves are transmitted through telephone lines to another modem, which converts them back into digital signals. An internal modem is installed on a circuit board inside the computer’s chassis. An external modem sits in a box linked to the computer’s serial port. Both types use phone cables to connect to the telephone network through standard modular phone jacks. Modems differ in their transmission speeds, measured in bits per second (bps).
EXAMPLE OF TWO PC’S CONNECTED TO ANETWORK HUB AND EXAMPLE OFWIRELESS MODEM
7.1.2 NETWORKS NEAR AND FAR A local area network (LAN) is a network in which the computers are close to each other, usually in the same building. Cables serve as information highways for transporting data between devices. A typical local area network includes a collection of computers and peripherals; each computer and shared peripheral is an individual node on the network. In a wireless network each computer has a tiny radio connected to its serial port so it can send and receive data through the air rather than through cables. All computers on a LAN do not have to be the same brand, or use the same operating system. Most organizations depend on network administrators to take care of the behind-the-scenes details so others can focus on using the network. A wide area network (WAN), as the name implies, is a network that extends over a long distance. Wide area networks are possible because of the web of telephone lines, microwave relay towers, and satellites that span the globe. Some WANs are private operations. Others are public or semi - public networks.
7.2 ELECTRONIC MAIL ANDTELECONFERENCING: INTERPERSONALCOMPUTING Electronic mail (e-mail) systems allow users to send messages (mail) from one computer to another. Each user has a mailbox—a storage area for messages. Users select a login name or screen name—the one- word or phrase name they have chosen to identify the user on the screen. A user then enters a password—a string of letters and numbers known only by the user— and as it is typed only asterisks appear on the screen. A variation of electronic mail is the teleconference— an on-line meeting between two or more people. Many teleconferencing systems allow users to communicate in real time, just as they would by telephone. In a real-time teleconference, each participant sits at a computer or terminal, watching the meeting transcript scroll by on the screen and typing comments on the keyboard.
7.3.1 ELECTRONIC BULLETINBOARD SYSTEMS (BBSS) An electronic bulletin board system (BBS) is a place for posting messages and reading messages left by others. BBS software allows the computer to receive, organize, and post messages in appropriate categories automatically. Many BBSs operate without human supervision for long periods of time. The system operator, or sysop, is needed only for occasional maintenance and troubleshooting. Many BBSs divide messages into categories called SIGs, for special interest groups. In addition, many bulletin boards serve as repositories for public domain software and shareware—two types of software that can be freely distributed without violating copyright laws. BBS users can download software—copy it from the BBS computer to their computers— and upload software—post it on the BBS so it’s available for others. Software
7.4 TELECOMMUNICATION TRENDS:MERGING AND EMERGINGTECHNOLOGIES 7.4.1 Alternative Communication Technologies The following forms of telecommunication don’t require users to type commands and messages. Facsimile Transmission A facsimile (fax) machine is a fast and convenient tool for transmission of information stored in paper documents, such as typed letters, handwritten notes, photographs, drawings, book pages, and news articles. A computer can send on-screen documents through a fax modem to a receiving fax machine. The fax modem translates the document into signals that can be sent over phone wires and decoded the receiving fax machine. A computer can also use a fax modem to receive transmissions from fax machines, treating the sending fax machine as a kind of remote scanner. Before a faxed document can be edited, it must be processed by optical character recognition (OCR) software.
VOICE MAIL AND COMPUTERTELEPHONY A voice mail system is more than an answering device; it’s a sophisticated messaging system with many of the advantages of e-mail. Computer telephony software and hardware allow a personal computer to serve as a speakerphone, answering machine, and even as a voice mail system. Video Teleconferencing A video teleconference allows people to communicate face to face over long distances by combining video and computer technology. Video teleconferencing comes to the desktop with video phones and video teleconferencing software.
ELECTRONIC FUNDS TRANSFER(EFT) Money, like other digital information, can be transmitted through computer networks. That’s why it’s possible to withdraw cash from your checking account using an automated teller machine (ATM) at a bank, airport, or shopping mall thousands of miles from your home bank. An ATM is a specialized terminal linked to a bank’s main computer through a commercial banking network. Many people have paychecks deposited automatically in checking or savings accounts and have bills paid automatically out of those accounts. Electronic funds transfer is one component of electronic commerce, or e-commerce —commercial activity that takes place through networked computers. Personal Digital Assistants
PERSONAL DIGITAL ASSISTANTS Many personal digital assistants (PDAs) combine cellular phone, fax modem, an electronic mailbox, a pager, and other communication equipment in a lightweight box. These devices are popular with a growing number of mobile professionals.
7.4.2 CONVERGINGCOMMUNICATIONTECHNOLOGIES ISDN The Integrated Services Digital Network, commonly called just ISDN, will link telephones, computers, fax machines, television, and even mail in a single digital system. ISDN is already available in a few cities, but most phone lines can’t handle ISDN. The main problem is bandwidth—the quantity of information that can be transmitted through a channel in a given amount of time. The bandwidth bottleneck disappears when copper phone lines are replaced with high-capacity fiber optic cables. Fiber optic cables use light waves to carry information at blinding speeds. Digital Communication Comes Home Integrated digital communication lines will eventually find their way into our homes, radically changing our lives in the process.