Address Resolution Protocol (ARP)

An Internet protocol for resolving an IP address into a physical layer address (such as an Ethernet media access control address). See also Physical Layer, Internet Protocol.

Advanced Research Projects Agency Network (ARPANET)

Predecessor to the Internet that was developed by the Department of Defense in the late 1960s.

AppleTalk

The built-in (to firmware) suite of network protocols that Macintosh computers use. Windows NT Server uses AppleTalk to service Macintosh clients by simulating an Apple server. Sec also Macintosh, Network Protocol.

Administrators

Users who are part of the Administrators group. This group has the ultimate set of security permissions. See also Administrator Account, Permissions, Groups.

Encryption

The process of obscuring information by modifying it according to a mathematical function known only to the intended recipient. Encryption secures information being transmitted over non- secure or untrusted media. See also Security.

Home Directory

A directory that stores a user's personal files.

Directories

 In a file system, directories are containers that store files or other directories. Mass storage devices have a root directory that contains all other directories, thus creating a hierarchy of directories sometimes referred to as a directory tree. See also File, File System.