System Unit,Input & Output and Secondary Storage

Modulation
-is a process of varing one or more properties of high frequency periodic waveform- carrier signal
-contains information to be transmitted.
-done in a similar fashion to a musician modulating a tone (a periodic waveform) from a musical instrument by varing its volume, timing and pitch.
-enable the carrier signal to transport the information in the modulation signal to some destination.

Demodulation

- is the act of extracting the original information bearing signal from a modulated carrier wave.

-used in connection with radio receivers, but many other systems use many kinds of demoulators.

-A demodulator is an electronic circuit (or computer program in a software defined radio) that is used to recover the information content from the modulated carrier wave.

Bandwidth

- a rate of data transfer, bit rate or throughput, measured in bits per second (bps)

-linear algebra, the width of the non zero terms around the diagonal of a matrix.

-describes the width of the convolution kernel used

-a normative expected range of linguistic behaviour in language expectancy theory.

TCP/IP

-a model which a description framework for computer network protocols created in the 1970s  by DARPA

-evolved from ARPANET which was the world first wide area network and a predecessor of the Internet.

- can be called as Internet model or the DoD Model

-describes a set of general design guidelines and implementations of specific networking protocols

-provides end to end connectivity specifying how data should be formatted, transmitted, routed and received at the destination.

Node

-in Latin node pronouced as nodus, 'knot'

-a connection point, either a redistribution point or a communication endpoint (some terminal equipment).

-definition of a node depends on the network and protocol layer referred to.

- a physical network node is an active electronicdevice that is attached to a network, and is capable of sending, receiving or forwarding information over a communications channel.

Client

- an application or system that accesses a remote service on another computer system

-known  as a server , is the way of a network

-first appled todevices that were not capable of running their own stand alone programs.

-able to interact with remote computers via a network

-can run on the same machine and connect via Unix domain sockets.

-might connect to a service operating on a possibly remote system through the Internet protocol suite.

Server

- a server application, operating system, computer or applicance

Examples:

• Application server, a server dedicated to running certain software applications
• Catalog server, a central search point for information across a distributed network
• Communication server, carrier grade computing platform for communications networks
• Database server, provides database services to other computer programs or computers
• File server, provides file services

Network Operating System

- is referred to as the Dialoguer which is the software that runs on a server

-enables the server to manage data, users, groups, security, applications and other networking functions.

-designed to allow shared file and printer access among multiple computers in a network, typically a (LAN)

-Examples of NOS - Microsoft Winows Server 2003, Microsoft Windows Server 2008, UNIX and LINUX.

Network Administrator

-is a person responsible for the maintance of computer hardware and software that comprises a computer network.
-includes deploying, configuring, maintaing and monitoring active network equipment.
- is normally at the level of technical or network staff in organizations.
- will concentrate on the overall integrity of the network, server deployment, security, and ensuring that the network connectivity throughout a company's WAN infrastructure is on par with technical consideartions at the network level of an organization's hierachy.

Secondary Storage

Disk Caching

Disk cache may refer to:
-Disk buffer, the small amount of buffer memory present on a hard drive.
-Page cache, the cache of disk pages kept by the operating systems, stored in unused main memory.
-General application-level caching of data stored on the disk.
-Readyboost, a non-volatile disk cache stored on flash memory device,in Windows Vista and Windows 7.

File Compression

- allows users to make one or more files into a smaller zip file.
-is  the process of encoding information using fewer bits than the original representation would use.
-helps reduce the consumption of expensive resources, such as hard disk space or transmission bandwidth.

File Decompression

-reduces the size of a file by minimizing redundant data.

- redundant data can be frequently occuring characters, such as the space character, or common vowels, such as the letters e and a.

-Data compression creates a compressed version of a file by minimizing this redundant data.

Internet hard Disk

- a magneticdisk on which you can store computer data.
- Hard is used to distinguish it from a soft, floppy, disk.
-consists of several platters, one platter needs two read/write heads, one for each side.
-attacted to a single access arm for not moving indepently.
-Has the same numeber of tracks, and a track location that cuts across all platters is called a cylinder.

Optical Disk Drive

- a disk drive that uses laser light or electromagnetic waves near the light spectrum as part of the process of reading or writing data to or from optical discs.

- an integral part of stand-alone consumer appliances such CD players, DVD players and DVD recorders.

- some can oly read from discs, but recent drives are both generally readers and recorders.

-these recorders can be called or known as burners or writers.



Solid State Storage

- a data storage device that uses solid-state memory to store persistent data with the intention of providing access in the sane manner of a manner of traditional block i/o hard disk drive.
-known as SSD ( solid state drive)
-devices contain spinning disks and moveable read/write heads.
-use microchips which retain data in non-volatile memory chips and contain no moving parts.

Input and Output

Ergonomic Keyboard

- a computer keyboard designed with ergonomic considerations
- minimize muscle strain and a host of related problems.
- constructed in V shape ,allows right and left hands to type at a slight angle more natural to human form.
- such as split keyboard, contoured keyboard and angled split keyboard.

Inkjet Printer

- A class of printer in which small ink droplets are sprayed electrostatically from a nozzle onto a paper.
- Very quiet in comparison to impact printers.
- Example, Olivetti BJ 10.

Laser Printer

- A common type of computer printer that rapidly produces high quality text and graphics on plain paper.
- with digital photocopies and multifunction printers (MFPs)
- employ a xerographic printing process,  but differ from analog photocopiers in that the image is produced by the direct scanning of a laser beam across the printer's photoreceptor.


Magnetic- ink Character Recognition

- known as MICR
- used by banking industry to facilitate the processing of cheques
- allows technology to read numbers or information off printed documents.
-characters are printed in special typefaces with a magnetic ink or toner which contains iron oxide.
-Character pass over the head before it produces an unique waveform which can be identified by the system.

Optical- character Recognition

- recognized as OCR
- Mechanical translation of scanned images of handwritten, typewritten or printed text into machine- encoded text
- convert books, documents into electronic files, to computerize a record- keeping system in an office or to publish text on websites.
-possible in editing the text, searching vocabularies or phase, storing it more compactly, displaying or printing a copy free of scanning artifacts and apply techniques.

Optical Mark Recognition

- work with dedicated scanner device that shines a beam of light onto the form paper.
-using form which are preprinted onto 'transoptic' paper and measure the amount of light which passes through the paper, thus a mark on either side of the paper will reduce the amount of light passing through the paper.