computerr science 1,2

• WAN


  Wide area network (network covering a very large geographical area)
• LAN


  Local area network (network covering a small area such as a single building)
• MAN


  Metropolitan area network (network which is larger than a LAN but smaller than a WAN, which can cover several buildings in a single city, such as a university campus)
• File server


  A server on a network where central files and other data are stored. They can be accessed by a user logged onto the network
• Hub


  Hardware used to connect together a number of devices to form a LAN that directs incoming data packets to all devices on the network (LAN)
• Switch


  Hardware used to connect together a number of devices to form a LAN that directs incoming data packets to a specific destination address only
• Router


  Device which enables data packets to be routed between different networks (for example, can join LANs to form a WAN)
• Modem


  Modulator demodulator. A device that converts digital data to analogue data (to be sent down a telephone wire); conversely it also converts analogue data to digital data (which a computer can process)
• WLAN


  Wireless LAN
• (W)AP


  (Wireless) access point which allows a device to access a LAN without a wired connection
• PAN


  Network that is centred around a person or their workspace
• Client-server


  Network that uses separate dedicated servers and specific client workstations. All client computers are connected to the dedicated servers
• Spread spectrum technology


  Wideband radio frequency with a range of 30 to 50 metres
• Node


  Device connected to a network (it can be a computer, storage device or peripheral device)
• Peer-to-peer


  Network in which each node can share its files with all the other nodes. Each node has its own data and there is no central server
• Thin client


  Device that needs access to the internet for it to work and depends on a more powerful computer for processing
• Thick client


  Device which can work both off line and on line and is able to do some processing even if not connected to a network/internet
• Bus network topology


  Network using single central cable in which all devices are connected to this cable so data can only travel in one direction and only one device is allowed to transmit at a time
• Packet


  Message/data sent over a network from node to node (packets include the address of the node sending the packet, the address of the packet recipient and the actual data – this is covered in greater depth in Chapter 14)
• Star network topology


  A network that uses a central hub/switch with all devices connected to this central hub/switch so all data packets are directed through this central hub/switch
• Mesh network topology


  Interlinked computers/devices, which use routing logic so data packets are sent from sending stations to receiving stations only by the shortest route
• Hybrid network


  Network made up of a combination of other network topologies
• Cloud storage


  Method of data storage where data is stored on off-site servers
• Data redundancy


  Situation in which the same data is stored on several servers in case of maintenance or repair
• Wi-Fi


  Wireless connectivity that uses radio waves, microwaves. Implements IEEE 802.11 protocols
• Bluetooth


  Wireless connectivity that uses radio waves in the 2.45 GHz frequency band
• Spread spectrum frequency hopping

  A method of transmitting radio signals in which a device picks one of 79 channels at random. If the chosen channel is already in use, it randomly chooses another channel. It has a range up to 100 metres
• WPAN


  Wireless personal area network. A local wireless network which connects together devices in very close proximity (such as in a user's house); typical devices would be a laptop, smartphone, tablet and printer
• Twisted pair cable


  Type of cable in which two wires of a single circuit are twisted together. Several twisted pairs make up a single cable
• Coaxial cable


  Cable made up of central copper core, insulation, copper mesh and outer insulation
• Fibre optic cable


  Cable made up of glass fibre wires which use pulses of light (rather than electricity) to transmit data
• Gateway


  Device that connects LANs which use different protocols
• Repeater


  Device used to boost a signal on both wired and wireless networks
• Repeating hubs


  Network devices which are a hybrid of hub and repeater unit
• Bridge


  Device that connects LANs which use the same protocols
• Softmodem


  Abbreviation for software modem
• Softmodem


  Abbreviation for software modem; a software-based modem that uses minimal hardware
• NIC


  Network interface card. These cards allow devices to connect to a network/internet (usually associated with a MAC address set at the factory)

  
• WNIC


  Wireless network interface cards/controllers
• Ethernet


  Protocol IEEE 802.3 used by many wired LANs