bitmap--Sequential bits used to graphically represent images.

cache--Area of computer memory set aside for temporary storage of data that has most recently been taken from main memory.

checksumSimple error detection method. A value is derived by using the output of a mathematical computation performed on a block of data to determine if any of the data has been corrupted.

clusterNumber of computers connected by a high-speed network to function as a single large computer with many central processing units.

cracker--Technically, the correct term for what has become the definition of a hacker. One who attempts to exceed his level of access to a computer system.

encryption--Process of turning understandable text into gibberish so that anyone who gains access to a file will not be able to read its actual contents without using the encryption key or password. Converting the gibberish back into an understandable form is call decryption.

inode--Index node containing file descriptor information for a single file which the system needs to access and manage the file, e.g. the size and type of the file, where the file is stored, who owns and has access to the file, etc.

superblock--Second region of storage space in a file system that is always retained in main memory. Contains information required to maintain a file system. This information defines the location of data in the file system, and includes fixed information, such as file system size, and changing information, such as the location of free blocks.