Communication and Network

Modulation

It is the transmission of a signal by using it to vary a carrier wave, changing the carrier's amplitude, frequency or phase. Besides that, it is the process of conveying a message signal. Modulation is the process of converting digital signal to analog signal. Modem is the device that is used for the modulation process.

Demodulation

It is a process of retrieving data or message conveyed from the modulator. Besides that, it interprets and changes the signal delivered by the modulator. Demodulation process converts analog signal to digital signal. Modem, the same device used for the modulation process is also used in this process.

Bandwidth

It is a measurement of data that can be carried from one point to another in a given time period. Bandwidth is usually measured in bits (of data) per second (bps). For example, to transfer texts or documents, a slow bandwidth is used and to transfer audio or video files, a wider bandwidth is needed. There are three types of bandwidth which are voiceband (used for dial-up service), medium band (leased lines) and broadband (used for DSL and high capacity transmission).

TCP/IP


Short for transmission control protocol/internet protocol, it is the standard protocol or rules for the Internet. It allows different kinds of computers on different networks to communicate. Therefore, connecting them by a "universal" language. The essential features of TCP/IP is are identification and packetization. Identification is to identify sending and receiving devices whereas packetization reformats the information for transmission across the Internet. For identification, the internet uses IP address to deliver email and locate websites and the domain name server (DNS) converts the text-based adress to IP address. The function is the similar to a postal address. Packetization transmits information through interconnected networks. Before a message is sent, it is reformatted into packets and each packet is sent separately through the Internet. These packets are then reassemble into the correct order when received.


Node

It is a connection point for networks. It can be any device connected to a network. For example, a computer, printer, a data storage device or an active electronic device that is attached to a network. Besides that, it is capable of sending, receiving or forwarding information over a communications channel.

Client

It is a node that requests and uses resources available from other nodes. Basically, a client is a user’s microcomputer. Besides that, a client is capable of obtaining information and applications from a server. Clients make "requests" through a network or networks, and receive "responses" from servers.

Server

It is a a node that shares resources with other nodes. Servers provide essential services across a network through the Internet. There are many servers and each of them are assigned to a specific task. Dedicated servers that are assigned to a specific tasks are  web servers, print servers, and database servers.

Network Operating Systems

It is an operating system that has special functions for connecting computers and devices into a local-area network (LAN). NOS controls and coordinates activities of all computer and devices on the network. Such activities include electronic communication and the sharing of information and resources. Examples of networking operating systems are Novell Netware, Artisoft's LANtastic, Microsoft Windows Server, and Windows NT.

Network Administrator

A computer specialist who manages a communications network in an organization. Responsibilities include implementing new networks, maintaining network operations efficiently and network security. Besides that, installing new hardware and applications, monitoring software upgrades, enforcing licensing agreements, developing a storage management program and providing for routine backups.

Secondary Storage

Disk Caching

A portion of RAM used to speed up access to data on a disk. The RAM can be part of the disk drive itself (sometimes called a hard disk cache or buffer) or it can be general-purpose RAM in the computer that is reserved for use by the disk drive (sometimes called a soft disk cache). Hard disk caches are more effective, but they are also much more expensive, and therefore smaller. Nearly all modern disk drives include a small amount of internal cache. 

A soft disk cache works by storing the most recently accessed data in the RAM cache. When a program needs to access new data, the operating system first checks to see if the data is in the cache before reading it from the disk. Because computers can access data from RAM much faster than from a disk, disk caching can significantly increase performance. Many cache systems also attempt to predict what data will be requested next so they can place that data in the cache ahead of time.

File Compression

Compression is the reduction in size of data in order to save space or transmission time. For data transmission, compression can be performed on just the data content or on the entire transmission unit (including header data) depending on a number of factors. 

Content compression can be as simple as removing all extra space characters, inserting a single repeat character to indicate a string of repeated characters, and substituting smaller bit strings for frequently occurring characters. This kind of compression can reduce a text file to 50% of its original size.

File Decompression

Decompression of file archives can be achieved on all computers, but live decompression of video requires much more powerful hardware.Decompressing image files does not require significant amounts of processing power and so it can be done on-the-fly.

Internet Hard Drive

Free online backups allow you to store backups of your files offsite. If any disaster should occur at your location (perish the thought), at least you can still access the backup copy of your files since it's probably kept in a different part of the country (or even world - depending on where you are relative to the service). You can then access your files and even share them from anywhere. Some of the services allow you to automatically schedule backups, and keep different versions (or generations) of your files, so, if for example, if you are working on a file all day, and find that you deleted an important section of your document in your latest "save", you can recover an earlier version of the saved and backed up file (something like version control software except that this is primarily a backup solution). Some, if not all, of the backup solutions also encrypt your files, hopefully making it inaccessible to anyone except those with a password. 

Optical Disk Drive

A storage medium from which data is read and to which it is written by lasers. Optical disks can store much more data -- up to 6 gigabytes (6 billion bytes) -- than most portable magnetic media, such as floppies.

Solid-state storage

Solid-state storage is a nonvolatile, removable storage medium that employs integrated circuits (ICs) rather than magnetic or optical media. It is the equivalent of large-capacity,nonvolatile memory. Examples include flash memory Universal Serial Bus (USB) devices and various proprietary removable packages intended to replace external

 external hard drive. 

The main advantage of solid-state storage is the fact that it contains no mechanical parts. Everything is done electronically. As a result, data transfer to and from solid-state storage media takes place at a much higher speed than is possible with electromechanical disk drives. The absence of moving parts may translate into longer operating life, provided the devices are reasonably cared for and are not exposed to electrostatic discharge.

Input and Output

Ergonomic Keyboard
A keyboard that separates the keys into two halves shaped like a wide "V." Some keyboards have a fixed layout, while others are movable. To the touch typist, the layout feels odd at first, but it puts less stress on the hands and wrist and winds up being comfortable for most people

Inkjet Printer

A type of printer that works by spraying ionized ink at a sheet of paper. Magnetized plates in the ink's path direct the ink onto the paper in the desired shapes. Ink-jet printers are capable of producing high quality print approaching that produced by laser printers. A typical ink-jet printer provides a resolution of 300 dots per inch, although some newer models offer higher resolutions. 

In general, the price of ink-jet printers is lower than that of laser printers. However, they are also considerably slower. Another drawback of ink-jet printers is that they require a special type of ink that is apt to smudge on inexpensive copier paper. 

Because ink-jet printers require smaller mechanical parts than laser printers, they are especially popular as portable printers. In addition, color ink-jet printers provide an inexpensive way to print full-color documents.

Laser Printer

A type of printer that utilizes a laser beam to produce an image on a drum. The light of the laser alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions of the drum. Finally, the toner is transferred to the paper through a combination of heat and pressure. This is also the way copy machines work. 

Because an entire page is transmitted to a drum before the toner is applied, laser printers are sometimes called page printers. There are two other types of page printers that fall under the category of laser printers even though they do not use lasers at all. One uses an array of LEDs to expose the drum, and the other uses LCDs. Once the drum is charged, however, they both operate like a real laser printer.

Magnetic-ink character recognition

Magnetic Ink Character Recognition is a character recognition system that uses special ink and characters. When a document that contains this ink needs to be read, it passes through a machine, which magnetizes the ink and then translates the magnetic information into characters.

Optical-character recognition

Often abbreviated OCR, optical character recognition refers to the branch ofcomputer science that involves reading text from paper and translating the images into a form that the computer can manipulate (for example, into ASCII codes). 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. 

All OCR systems include an optical scanner for reading text, and sophisticated software for analyzing images. Most OCR systems use a combination of hardware (specialized circuit boards) and software to recognize characters, although some inexpensive systems do it entirely through software. Advanced OCR systems can read text in large variety of fonts, but they still have difficulty with handwritten text.

Optical-mark recognition

The technology of electronically extracting intended data from marked fields, such as checkboxes and fill-infields, on printed forms. OMR technology scans a printed form and reads predefined positions and records where marks are made on the form. This technology is useful for applications in which large numbers of hand-filled forms need to be processed quickly and with great accuracy, such as surveys, reply cards, questionnaires and ballots. A common OMR application is the use of "bubble sheets" for multiple-choice tests used by schools. The student indicates the answer on the test by filling in the corresponding bubble, and the form is fed through an optical mark reader (also abbreviated as OMR, a device that scans the document and reads the data from the marked fields. The error rate for OMR technology is less than 1%.