Twisted-Pair Cable
Twisted-pair cables is a type of wiring that consists of two cables that is twisted together to cancel out Eloctromagnetic Interference (EMI) from external sources. Most networks contain some twisted-pair cabling at some point along the network while twisted-pair cable is used by older telephone networks and is the least expensive type of LAN cable.
Coaxial Cable
A type of wire that consists of a center wire surrounded by insulation and then a grounded shield of braided wire. The shield minimizes electrical and radio frequency interference. Coaxial cable (or "coax") is the most common cable used for transmitting video signals. The name "coaxial" refers to the common axis of the two conductors. It is widely used for computer networking as it is much less susceptible to interference and can carry much more data.
Fiber-Optic Cable
Fiber-Optic cable is a technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves. The main disadvantage of fiber optics is that the cables are expensive to install. In addition, they are more fragile than wire and are difficult to splice.
Node
Node is a region in an electrical circuit where there is no change in potential. Node is also a connection point, either a redistribution point or an end point for data transmissions. In general, a node has programmed or engineered capability to recognize and process or forward transmissions to other nodes.
Client
A client is an application or system that accesses a remote service on another computer system, known as a server, by way of a network. The term was first applied to devices that were not capable of running their own stand-alone programs, but could interact with remote computers via a network. These dumb terminals were clients of the time-sharing mainframe computer.
Server
A server is an application running on a computer that delivers a service. For example, a web server will deliver web pages when requested by a browser (called client in this context). The way a server and a client dialogs is called a protocol. For instance, HTTP is the protocol used between a browser and a web server. Among the many services provided by the Internet servers are:
1) World Wide Web
2) the domain name system
3) e-mail
4) FTP file transfer
5) chat and instant messaging
6) voice communication
7) streaming audio and video
8) online gaming
Hub
Hub is a common connection point for devices in a network and commonly used to connect segments of a LAN. It also contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.
Network Interface Card ( NIC)
NIC is an expansion board you insert into a computer so the computer can be connected to a network. Most NICs are designed for a particular type of network, protocol, and media, although some can serve multiple networks.
Network Operating System (NOS)
NOS is a network operating system. A network operating system implements protocol stacks as well as device drivers for networking hardware. Some network operating systems, like Windows 98 Second Edition, also add custom networking features like Internet Connection Sharing (ICS).
Host Computer
Network Manager
Network Terms
Secondary Storage
Disk Caching is a process for improving the time it takes to read from or write to a hard disk.The disk cache is usually included as part of the hard disk. A disk cache can also be a specified portion of random access memory (RAM).
The disk cache holds data that has recently been read and, in some cases, adjacent data areas that are likely to be accessed next. Write caching is also provided with some disk caches.
RAID is a technology that allowed computer users to achieve high levels of storage reliability from low-cost and less reliable PC-class disk-drive components, via the technique of arranging the devices into arrays for redundancy.
For the large business organizations, which not only need to store terabytes of invaluable data but access them frequently as well. These organizations cannot afford to let their systems go offline even for a short duration of time. Moreover they cannot even think of losing even small amount of data due to disk failure or for that matter any other reason.
File compression and decompression
Input and Output
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Magnetic Ink Character Recognition (MICR)
MICR is a character recognition technology used primarily by the banking industry to facilitate the processing of cheques and allows computers to read information (such as account numbers) off of printed documents. MICR font is usually used to print checks, deposit slips, mortgage coupons, etc.
There are various types of MICR fonts:
- MICR E-13B font is used in the Canada, Panama, Puerto Rico, UK, and the United States.
- MICR CRC-7 was created according to the ISO standards and is a font used in France, Mexico, Spain, and most other Spanish speaking countries.
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Optical-Character Recognition (OCR)
OCR is the mechanical translation of images of handwritten, typewritten or printed text (usually captured by a scanner) into machine-editable text.An OCR system enables you to take a book or a magazine article, feed it directly into an electronic computer file, and then edit the file using a word processor.
The potential of OCR systems:
- They enable users to harness the power of computers to access printed documents.
- They are being used in the legal profession, where searches that once required hours or days can now be accomplished in a few seconds.
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Optical-Mark Recognition (OMR)
OMR is the technology of electronically extracting intended data from marked fields, such as checkboxes and fill-in fields, on printed forms which it was distinguished from OCR that do not required any recognition engine.
OMR is useful for applications:
- Large numbers of hand-filled forms need to be processed quickly and accurately, such as surveys, reply cards, questionnaires and ballots.
Dot-matrix Printer
Dot-matrix Printer which also known as impact matrix printer is a type computer printer with a print head that runs back and forth, or in an up and down motion, on the page and prints by impact, striking an ink-soaked cloth ribbon against the paper, much like a type writer. These printers can create carbon copies and carbon-less copies because the printing involves mechanical pressure.
Dot-matrix printers vary in two important characteristics:
- Speed: Given in character per seconds (cps), the speed can vary from about 50 to over 500 cps. Most dot-matrix printers offer different speeds depending on the quality of print desired.
- Print quality: Determined by the number of pins (the mechanisms that print the dots), it can vary from 9 to 24. The best dot-matrix printers (24 pins) can produce near letter-quality type, although you can still see a difference if you look closely.
Plotter
A plotter is a vector graphics printing devices to print graphical plots that connects to computer. Plotters differ from printer in that they draw lines using a pen which can results a continuous lines, whereas printers can only simulate lines by printing a closely spaced series o dots. Multicolor plotters use different-colored pens to draw different colors.
There are two types of main plotters:
- Pen plotters
- Electrostatic plotters.
Photo Printer
A photo printer is a printer (usually an inkjet printer) that is specifically designed to print small and high quality digital photos on photo paper (4x6" and 5x7"). These printers usually have a very high number of nozzles and are capable of printing droplets as small as 1 picoliter.
Portable Printer
Portable is used as electronics miniaturizes and increases in quality and cropping up new novelties. This technology can print from camera phones, digital camera or memory cards.
Fax Machine
A fax machine is a device that prvided scan, transmits, receives and prints documents (faxes) transmitted by telephone and allows the user to fax information over a communication line. A fax machine is one of the most invaluable methods of transmitting information that was ever invented. It has allowed transactions ranging from sending letters and photos between loved ones to finalizing major corporate mergers.
Multifunctional Device
Multifunctional device is a device that serves several functions, including printing. In short, it can act as a printer, a scanner, a fax machine and a photocopier.
The disadvantages of combining all these functions in one device are:
- If the device breaks, you may lose all of its functions at the same time.
- You can only do one operation at a time. For example, you can't print a document and receive a fax at the same time.
Internet Telephones
An Internet phone service uses the Internet to send voice instead of using phone lines. Home services have softphones: your computer becomes your telephone, and you talk via a handset or a headset plugged into USB ports. Internet telephony products are called IP telephony, Voice over the Internet (VOI) or Voice over IP (VOIP) products.
There are many Internet telephony applications available:
- Popular web browsers- CoolTalk and NetMeeting.
- stand-alone products.
Voice Over Internet Protocol (VOIP)