Computer Terms - Letters E through H
EBCDIC (extended binary coded decimal interchange code): 8-bit character encoding table used by ISM mainframes
EGP (exterior gateway protocol): a protocol commonly used between hosts on the Internet to exchange routing table information
EMI (electromagnetic interference): radiation that causes unwanted signals (interference or noise) to be induced in other circuits; also called radio frequency interference or RFI
Enterprise network: connects many types of networks
Ethernet: most commonly used protocol designed to change the packets into electrical signals that can be sent out over the wire
Exterior protocols: routing protocol used between autonomous systems
FAT (file allocation table): table that the operating system uses to locate files on a disk; because a file may be divided into many sections that are scattered around the disk, the FAT keeps track of all the pieces
FDDI (fiber distributed data interface): a set of ANSI protocols for sending digital data over fiber optic cable (see ANSI)
FDM (frequency-division multiplexing): permits a range of input signals to be carried over a communication line that uses separate carrier frequencies for each signal channel; mostly used for analog information but can carry digital
File management system: way to store and retrieve information from disk drives; controls how files can be created, accessed, retrieved, and deleted
Firewall: a barrier between a network and the Internet through which only authorized users can pass; set of security policies to screen incoming and outgoing messages; also used to isolate one part of a network from another
Floppy drive: early versions were actually floppy; today, they use hard 3.5 inch disk; also referred to as removable drive
Frame: data structure that collectively represents the transmission stream (headers, data, and the trailer) and provides the information necessary for the correct delivery of the data
Frame relay: service with standards and specifications designed to transmit data; some users have had success at transmitting voice
FRAD (frame relay access device): software that frames the customer’s payload with the Frame Relay overhead information, including the first DLCI (data link connection identifier) address, to prepare it for delivery to the network
Frequency: number of times a wave repeats a cycle in a one-second period; measured in cycles per second, or hertz
FTP (file transfer protocol): application used to transfer a copy of a file from one computer to another computer with one acting as client and the other as server; a login with a user name and password is typically required
Full-duplex link: enables both sides to simultaneously send and receive data; could require two separate cables, one in each direction or a single multiplexed cable
Gateways: a node on a network that translates (converts protocol) from one operating system environment to another
Gateway routers: used to implement exterior protocols and interconnect autonomous systems
Gbps (gigabits per second; billions of bits per second): a data transfer speed measurement for highspeed networks
GUI (graphical user interface): easy way of accessing applications with the use of a pointing device, such as a mouse; pronounced “gooey”
Half-duplex link: enables one side to transmit and receive, but not simultaneously; information only flows in one direction at a time using a control procedure to mediate
Host-to-host layer: part of the TCP/IP model that performs the same function as the transport layer in the OSI model
Host address: part of an IP address that is uniquely assigned by an administrator
HTTP (hypertext transfer protocol): protocol users interact with (by means of a browser) to access Web pages over an internet or intranet
Hubs: bring the users of the network into contact with one another
Hz (hertz): unit of frequency; one hertz simply means one cycle per second, applied to any periodic event (e.g., one tick of a clock is 1 Hz; the human heart beats at 1.2 Hz)
