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A network is a set of connected computer and devices to allow the sharing of resources and data. Image: download__1_ (image/jpg)	Image: download__1_ (image/jpg)
Networks can be classified by: SCALE:	THE SIZE AND REACH OF THE NETWORK E.G. PAN LAN CAN MAN WAN
L A N LOCAL AREA NETWORK	A NETWORK COVERING A SMALL GEOGRAPHIC AREA LIKE A HOME, OFFICE OR BUILDING
WAN WIDE AREA NETWORK	IS A DATA COMMUNICATIONS THAT COVERS A BROAD GEOGRAPHIC AREA e.g one city to another and one country to another
Backup	a duplicate of a file, program or disk that can be used if the original is lost, damaged or destroyed
to back up a file means	MEANS TO make a copy of it
information theft	occurs when someone steals personal or confidential information
ENCRYPTION	is a process of converting readable data into unreadable charters to prevent unauthorized access
unauthorized access	is the use of a computer or network without permission
unauthorized use	is the use of a computer or its data for unapproved or possibly illegal activites
Computer virus	affects a computer negatively by altering the way the computer works
worm	copies itself repeatedly, using up resources and possibly shutting down the computer or network
Trojan horse	A malicious program that hides within or looks like a legitimate program
ROOT KIT	Program that hides in a computer and allows someone from a remote location to take full control
COMPUTER SECURITY RISK	Is any event or action that could cause a loss of a damage to computer hardware, software,data information or processing capability
CYBER CRIME	IS AN ONLINE OR INTERNET BASED ILLEGAL ACT
SECONDARY STORAGE	non-volatile storage that is external to the main memory of a computer. it IS PERMANENT IT COST CHEAPER CAPACITY IS BIG IT HAS SPEED All our files are stored in secondary storage
STORAGE MEDIUM	is the physical material on which a computer keeps data, instructions, and information E.g. CDs, DVDs, hard drives Magnetic disks
Capacity	is the number of bytes a storage medium can hold
storage device	is the computer hardware that records and/or retrieves items to and from storage media
Why use Secondary Storage?	1) Any time we want to keep something permanently 2) It is good for backing up your files.
Hard Disk	iT consists of more than one magnetic disk in what is referred to as a disk platter, which is arranged one on top the other connected and rotate via a central spindle.
Cylinder concept	the same location on each plate where the top and bottom is filled before it continues to another
Formatting	It is the process of dividing the disk into tracks and sectors so that the operating system can store and locate data and information on the disk
Fixed Hard Drive	hard-drive built into the case of a computer is known as ‘fixed’. Almost every computer has a fixed hard-drive.
Portable Hard Drive	Portable hard-drives allow very large amounts of data to be transported from computer to computer.
RAID redundant array of independent disks	is a group of two or more integrated hard disks
network attached storage (NAS)	A network attached storage device is a server connected to a network with the sole purpose of providing storage
Access Time Access time = Rotational Delay + Seek Time	The time taken to access a record on the disk is determined by the Seek Time – i.e., the time taken for the head to move to the specified track) . The Rotational Delay Time (i.e., the time taken for the correct sector to come under the read/write head.
optical disc	It consists of a flat, round, portable disc made of metal, plastic, and lacquer that is written and read by a laser Typically store software, data, digital photos, movies, and music Read only vs. rewritable E.g. CD, CD-RW, DVD etc
Optical Discs	three main types of optical media: CD, DVD, and Blu-ray disc. A CD drive can only read CD discs, a DVD drive can only read DVD and CD discs, and Blu-ray can read CD, DVD, and Blu-ray discs.
CD-ROM	It can be read from but not written to Read from a CD-ROM drive or CD-ROM player
CD-R	It is a multi session optical disc on which users can write, but not erase
CD-RW	It is an erasable multi session disc Must have a * drive
magnetic tape	There are various types of *. They include:- Reel, Cartridge, and Cassette.
Magnetic Tape	is a data storage medium consisting of a magnetisable oxide (Iron Oxide) coating on a thin plastic strip, commonly used for backup and archiving.
Magnetic tape is a large capacity,	It is a large capacity, serial access medium. Because it is a serial access medium, accessing individual files on a tape is slow.
Types of Access Sequential Access	It- Refers to reading or writing data records in sequential order, that is, one record after the other. To read record 10, for example, you would first need to read records 1 through 9.
Types of Access: Random Access	They are – records can be read and written in any order
Types of Access Devices can also be classified as sequential access or random access	An example, a tape drive is a sequential-access device because to get to point q on the tape, the drive needs to pass through points a through p. disk drive, on the other hand, is a random-access device because the drive can access any point on the disk without passing through all intervening points.
Advantages of a Network:	Advantages of a Network: Facilitating communications Sharing hardware Sharing software Sharing data and information
Networks may be classified by	* may be classified by 1) Scale 2) Connection method 3) Network topology 4) Network architecture 5) Standards and Protocol
SCALE: Personal Area Network (PAN)	It is a computer network used for communication among computer devices close to one person. Some examples of devices that may be used in a PAN are printers, fax machines, telephones,
SCALE; Local Area Network (LAN)	A network covering a small geographic area, like a home, office, or building.
scale: Campus Area Network (CAN)	A network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, or a military base
scale: Metropolitan Area Network (MAN)	a network that connects two or more Local Area Networks or Campus Area Networks together but does not extend beyond the boundaries of the immediate town, city, or metropolitan area.
scale: Wide Area Network (WAN)	is a data communications network that covers a relatively broad geographic area (i.e. one city to another and one country to another country) and that often uses transmission facilities provided by common carriers, such as telephone companies.
Networks: collection methods	Computer networks can also be classified according to the hardware technology that is used to connect the individual devices in the network such as Optical fiber, Wireless, Coaxial, Ethernet, Radio Frequency, Microwave or Power line communication.
Ethernets	They are used physical wiring to connect devices. Often, they employ the use of hubs, switches, bridges, and routers
Network Topology	It signifies the geographical layout or logical arrangement of devices on a network.
Classification of Networks – Network Topology	Some examples of types of *: Bus Star Ring
Classification of Networks – Communication Standards & Protocol	Ethernet Token ring TCP/IP Wi-Fi Blue tooth UWB IrDA RFID WiMAX WAP
Classification of Networks – Communication Standards & Protocol TCP/ IP	* is a network standard that defines how messages are routed from one end of a network to another.
Computer communications	It describes a process in which two or more computers or devices transfer data, instructions, and information.
A communications device is	It is any type of hardware capable of transmitting data, instructions, and information between a sending device and a receiving device A dial-up modem converts signals between analog and digital A digital modem sends and receives data and information to and from a digital line A wireless modem uses the cell phone network to connect to the Internet wirelessly from a notebook computer, a smart phone, or other mobile device
Communications software consists	Communications software consists of programs that: Help users establish a connection to another computer or network Manage the transmission of data, instructions, and information Provide an interface for users to communicate with one another
bandwidth	The amount of data that can travel over a communications channel is called the *
Latency	It is the time it takes a signal to travel from one location to another on a network
Transmission media	It carries one or more signals
Broadband media	It transmit multiple signals simultaneously e.g DSL
inter network	Any interconnection among or between public, private, commercial, industrial, or governmental networks may be defined as an *
three variants of inter network,	There are at least three variants of internetwork, depending on who administers and who participates in them: Intranet Extranet Internet
Intranets and extranets may or may not have connections to the Internet.	Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.
An intranet	An * is a set of interconnected networks, using the Internet Protocol and uses IP-based tools such as web browsers, that is under the control of a single administrative entity. That administrative entity closes the intranet to the rest of the world, and allows only specific users
An extranet is a network or inter network	An * is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities (e.g. a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint).
Internet	A specific internetwork , consisting of a worldwide interconnection of governmental, academic, public, and private networks. It is also home to the World Wide Web (WWW) and referred to as the 'Internet' with a capital 'I' to distinguish it from other generic internetworks.
Classification of Networks: Ethernet	It is a network standard that specifies no computer controls when data can be transmitted.
Classification of Networks: Standards and Communication Token Ring	The * standard specifies that computers and devices on the network share or pass a special signal (token)

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	Created by Althea Baptiste about 11 years ago