Communication and Network

Twisted - Pair

• Least expensive and most widely used
• Consists of two insulated copper wire arranged in a regular spiral patter, act as a single communication link
• Used to transmit both analog and digital signals. Analog signals amplifiers are required about every 5 to 6 km. Digital signals, repeaters are required every 2 or 3 km.
• Commonly used medium for in the telephone network.
• Come in two varieties which are Unshielded Twisted Pair ( UTP ) Cable and Shielded Twisted Pair ( STP ) Cable.

• Coaxial Cable
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• • Contains thick, conductive metal wire at the center that is surrounded by meshed or braided metal shield along the same parallel axis.
  • Used for high-speed data transmission over distance of several kilometers.
  • Commonly used for radio antennae, cable TVs and LAN applications.
  • Can transmit signals greater distances and at a higher bandwidth.
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  Fiber - optic cable
  
  
• • Offers higher bandwidth and lower signal losses.
  • Allows higher data rates over longer distances.
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• Advantages of using :
• Information carrying capacity – Fiber optic capacities are well in excess of that required by today’s network applications. If the wavelength is different, the actual bandwidth can rise up to 5Cbps.
• Low signal loss – optical fibers offer low signal loss. It permits longer transmission distances. In comparison with copper, the longest recommended copper horizontal link is 100 meters; when using fiver it is 2000 meters or more.
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  Node
  
  
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  Client
  
• Communicates only with server, not with other clients.
• A standard PC that is running an operation system such as Windows 9x, Windows Me, Windows 2000 Professional, or Windows XP.
• Windows contain the client software that enables the client computers to access the resources that servers share.
• The connection in between the client and server is maintained only during the actual exchange of information.
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  Server
  
  
• Refers to the various type of software that process the requests from a visitors to a website.


• Used for running larger programs for multiple users often simultaneously and typically accessed only via a network.
• Maintained and housed by the institution or organization that sets up the CMC.
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  Hub
  
  
• Commonly used LAN connectivity devices ( although inexpensive switches are rapidly replacing hubs on networks)
• Serve as a central connection points for LANS.
• Contains no active electronics and therefore cannot be used to extend a LAN.
• Organizes your cable and relays data signals to all the computers on the LAN.
• Used on network that use twisted-pair cabling.
• A new HUB can be attached to the current HUB, thus providing greater port density.
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  Network Interface Card ( NIC )
  
  
• Hardware component that connects a station to the network medium.
• An adapter that plugs into a computer, enabling it to connect to a local area network(LAN) for the purpose of communicating with other computers and devices.
• Can be configured to improve the performance or security of data transfer between the station and the network.
• To improve network security, a NIC can be configured to apply encryption to all messages before transmission.
  
  Network Operation system ( NOS )
  
  
• Communicates with the PC hardware to make connection between the machines
• Provides basic file and supervisory services over a network.
• Provide a structure for access to application
• Enable users to manipulate programs and data
  
  Host Computer
  
  
  Receive calls from other computer and stores information that can be retrieved.
  Computer that access the host computer are called remote computers.
  
  Network Manager
  
  
• Provides one-stop shopping for all of your network configuration needs.
• Usually considered someone who maintains an existing network, making sure it runs as smoothly as possible, making adjustments for new users and programs and solving problems.

Secondary Storage.

Disk Caching

Object caching is a mechanism used by SharePoint to cache site, page, and page layout properties. Disk caching is used to cache BLOBs so that they do not have to be retrieved from the database. Object and disk caching are extremely fast and can significantly improve performance of sites, especially when large media files are involved. By default, object caching is always on, and disk caching is turned off. In order to enable disk caching, you must edit the web.config file for the web application where you want to use it.

Redundant arrays of inexpensive disks ( RAID )

A redundant array of inexpensive (or redundant) disks is a storage solution that uses multiple disks that function together to provide reliable data recovery. RAID can prevent the loss of data and/or improve performance. It can be used to provide connectivity when an organization’s primary ISP’s service becomes unavailable. RAID provides several methods of writing data across multiple disks, and writing to several disks. Rather than losing a single disks and all the information, administrators can replace the damaged risks and regenerate the data quickly.

File Comprassion and Decompression

The programs used to perform the compression and decompressions of image files are called codecs (compression decompression software). Many of them are integral parts of the most popular file formats for moving images like JPEG, MPEG-2, MPEG-4 and QuickTime, and some can compress and decompress the information on the fly. Compression is about reducing the size of the file so that the transmission time is shorter and the storage requirements are smaller. Decompression is about bringing back the data to a format that can be viewed with standard software.


Input source file → Compression Algorithm → Output compressed file

Input compressed file → Decompression Algorithm → Output decomposed file

Input and Output

Magnetic Ink Character Recognition (MICR)

All banks use MICR for processing cheques. Along the bottom of a cheque the bank’s sort code, customer account number and cheque number are encoded in special characters in magnetic ink. The amount of the cheque is encoded in magnetic ink when it is handed in at a bank. The cheque can be processed extremely fast by high-speed MICR devices that read, sort and store the data on disk. MICR has several advantages for processing cheque :
• It is hard to forge the characters
• The characters can be read even if the cheque is crumpled, dirty or smudged
• The characters are readable by humans, unlike bar codes.


Optical-Character Recognition ( OCR )

Optical- character recognition (OCR) is a tool for converting pages of text into computer-readable form. It automates the tedious of key entry, one of the lest rewarding ways of interacting with computers.

• Optical character recognition (OCR) uses a scanner and special software.
• OCR allows individual characters (letters of the alphabet, numbers, punctuation marks, etc.) to be recognized.
• It is an idea method for getting lots of text into a word-processing or desktop publishing package without the need for re-typing.
• It is sometimes used for recognizing account numbers on bills.


Optical-mark recognition ( OMR )

An optical mark reader can detect marks made in preset positions on a form. It is widely used for marking multiple-choice exams and market research questionnaires.
• The hardware device used is called an optical mark reader.
• An optical mark reader can only read marks on specially designed documents.
• OMR is ideal for reading the data from questionnaires, answers to multiple-choice examination question, menu choices in hospitals, football pools and lottery tickets.


Dot-matrix printer

A dot matrix printer is an impact printer, producing its image by striking the paper through a ribbon. Its print head consists of a number of small pins, varying between 9 and 24 depending on the manufacturer. A 24pin print head will produce a better quality of print than a 9 pin print head because the dots are closer together. As the print head moves across the page, one or more pins strike the ribbon and make a dot on the paper.

Plotter

A plotter is an output device used to produce high quality line drawings such as building plans or electronic circuits. They are generally classified as pen ( vector plotters) or penless ( raster plotters). The former use pens to draw images using point-to-point data, moving the pen over the paper. Pen plotters are low in price and hold a large share of the plotter market. Penless plotters include electrostatic potters, thermal plotters and laser plotters. They are generally used where drawings of high densities are required.


Photo Printer

a photo printer is optimized to create high-quality photo prints, typically on special photo print paper. Most consumer photo printer use inkjet technology. However, photo printer are notoriously slow ( 5 minutes or more to make a single print) and drink ink like its Gatorade on a hot summer day. When you add up the cost of ink cartridge and the special photo paper you have to use, you will find that a single print will cost you ten cents or so, an average.

Portable Printer

Portable printers are small, lightweight printers that can be used on the go, such as with a notebook computer, handheld PC, or smart phone. Some portable need to be physically connected to the computer, others can receive documents to be printed via a wireless connection. Portable printers that can print on regular-sized (8.5 by 11 inch) paper are used by business people while travelling; portable receipt and barcode printers are used in some service professions.

Fax machine

A fax machine is an essential piece of equipment in many health care facilities. This machine transmits data or information electronically over the telephone lines. For the system to work the sending and receiving facilities must each have a fax machine and a telephone line designated for the fax machine.

Multi-functional device

Multi-Function Device is Hardware that combines several functions in one unit. An MFP (Multi Function Product/ Printer/ Peripheral), multifunctional, all-in-one (AIO), or Multifunction Device (MFD), is an office machine which incorporates the functionality of multiple devices in one, so as to have a smaller footprint in a home or small business setting (the SOHO market segment), or to provide centralized document management/distribution/production in a large-office setting.

Internet Telephones

Internet telephony converts your voice into data packets, similar to what the traditional phone company does when sending voice over fiber cables for long distances. At the far end , the dara packets are converted back into sound signals and the voice you hear.
Internet telephony = VoIP = digital phone conversations = less dependence on the traditional phone companies = savings and more features.

System Unit

Expansion Card

An expansion card is an electronic circuit board that adds more functionality to a desktop computer. Expansion card also known as adapter card. It is a circuit board you install into a computer to increase the capabilities of that computer. Adapter cards come in many different kinds, but the important thing to note is that no matter what function a card has, the card being installed must match the bus type of the motherboard you are installing it into(for example, you can install a PCI network card only into a PCI expansion slot).

Network interface card

A network interface card (NIC) is an expansion card that connects a computer to a network so that it can communicate with other computers on that network. It translates the data from the parallel data stream used inside the computer into the serial data stream of packets used on the network. It has a connector for the type of expansion bus on the motherboard as well as a connector for the type of network. In addition to the NIC, you need to install software or drivers on the computer in order for the computer to use the network.

Cache memory



Cache memory is a high-speed and relatively small memory which Is used to hold the most frequently accessed contents of the main memory. The idea is that if most of the accesses made by a program are to a small subset of the main memory and if that subset can be brought into the cache, most of the program accesses will be done at cache speed. Caches are typically smaller than the main memory.

Plug and Play



Plug and play refers to the general ability of users of a computer system to “plug” new devices into the computer and immediately “play” with them (meaning that they are automatically configured and activated without having to restart the computer). Microsoft version of plug and play, which was introduced with Window95, was developed in the same spirit. However, it was also designed to initiate the installation of software drivers for devices that were not supported by the system by default.

Sockets


Network application use sockets to communicate over a TCP/IP network. A socket represents one end-point of a connection. A socket must be created for communication to take place. Because a socket is bidirectional, data can be sent as well as received though it.

Chips

A computer chip is a small electronic circuit, also known as an integrated circuit, which is one of the basic components of most kinds of electronic devices, especially computers. Computer chips are small and are made of semiconductors that are usually composed of silicon, on which several tiny components including transistors are embedded and used to transmit electronic data signals.


Slots

In computers, a slot, or expansion slot, are used to install various devices in the computer to expand its capabilities. Some expansion devices that may be installed in these slots include video, network, sound, and disk interface cards. Expansion slots come in three main types which are ISA, PCI AND AGP. Each type is different in appearance and function. Adapter cards are circuit boards that fit into expansion slots in the motherboard.

Bus lines

A system for splitting and connecting computer bus lines, including a ribbon cable with a flat end connector which is piggy-backed to the contact strip of a circuit board. The circuit board is then plugged into a bus slot with the flat end connector insulating selected terminal contacts of the slot from said contact strip. The ribbon connector is connected to the circuit board, the terminal contacts, the contract strip, or both. A control signal selector connected to the other end of the ribbon cable sends signals to one of several circuit boards so as to allow more than one work station to be supported by a single microprocessor.


Serial Port

A serial interface designed to transfer a stream of binary digit one but after another to some serial device like a modem, for example. The serial port was the old standby for connecting miscellaneous peripheral devices to a computer. It was used for everything from external modems to pointing devices. Some modems that connect the system unit to a telephone line use a serial port because the telephone line expects the data in a specific frequency.

Parallel port

A port on the computer in which communication is achieved by simultaneously sending binary data down different wires. A common parallel port on a PC is the printer port, although the USB (a serial port) is taking over this role on modern computer systems.

Universal Serial Bus

The Universal serial bus(USB) is a connection between a host computer and a number of peripheral devices.USB connection are capable of moving data faster than the older serial and parallel connections. Because USB connection are also hot swappable, you can safety plug in and unplug USB cables without shutting down your computer. USB allows high-speed, easy connection of peripherals to a PC. When plugged in, everything configures automatically.

Firewire Port

A firewire port is similar to a USB port in that it can connect multiple types of devices that require faster data transmission speeds, such as digital video cameras, digital VCRs, colour printer, scanners, digital cameras and DVD drives, to a single connector. A fireWire port allows you to connect up to 63 devices together. You can use FireWire hub to attach multiple devices to a single FireWire Port. A fireWire hub is a device that plugs in a FireWire port on the system unit and contains multiple FireWire ports in which you plug cables from FireWire devices. FireWire supports Plug and Play.

The internet, The Web and Electronic Commerce.

HTML


HTML is the short form for Hypertext markup language. HTML defines the organization and design of a Web document by using a variety of tags and attributes. When you write a normal document using a word processor like Microsoft Word/Office, your text is saved in a file with a special format. It is not simply saved as the string of words you typed since the document needs to conserve things like the font you chose, which words are in italics, which bold, and so on. The special format includes not only your words, but all these additional information so that the next time Word opens your document; it can display the document with the precise appearance you created earlier.


JavaScript


JavaScript is encoding language that is used to make web pages interactive, it is also an interpreted programming or script language from Netscape.
JavaScript is used in Web site advance to do such things as:
- mechanically change a formatted date on a Web page
- Cause a linked-to page to become visible in a popup window
- Cause text or a graphic image to change during a mouse rollover

Applets


An applet is a small program that works from within a larger application program. An applet has limited features but only requires limited memory resources. Applets are Java classes that you can execute in a Java-enabled browser such as Netscape Navigator or Internet Explorer. Before applets were introduced, Web sites consisted solely of static HTML content. It cannot operate on its own. Applets are written in the Java programming language. When you use a Java technology-enabled browser to view a page that contains an applet, the applet's code is transferred to your system and executed by the browser's Java Virtual Machine (JVM).

Business to Consumer (B2C)


Profit-making activity conducted between a company and an end consumer. B2C is often used to portray the retail part of ecommerce. It is also a form of electronic commerce in which products or services are sold from a firm to a consumer. B2C has grown to include services such as online banking, travel services, online auctions, health information and real estate sites.

Consumer to Consumer (e-Commerce)


Facilitates commerce between consumers. Communications and purchases that occur among individuals without directly involving the manufacturer or retailer. The most famous C2C Company is eBay, the world’s largest personal online trading community, which allows consumers to offer their good directly to other consumers in auction format.

File Transfer Protocol


File transfer protocol (FTP) is an internet service for transferring files between different machines. FTP uses clear-text username and password exchanges and is not considered to be a very secure utility. It automatically takes care of the details of how files are moved, provide a rich command syntax to allow various supporting file operations to be performed (such as navigating the directory structure and deleting files), and operates using the Transmission Control Protocol (TCP) transport service for reliability.

Filters


In computer programming, a filter is a program or section of code that is designed to inspect each input or output request for certain qualifying criteria and then process or forward it accordingly. This term was used in UNIX systems and is now used in other operating systems. A filter is "pass-through" code that takes input data, makes some specific decision about it and possible transformation of it, and passes it on to another program in a kind of pipeline. Usually, a filter does no input/output operation on its own. Filters are sometimes used to remove or insert headers or control characters in data.