MS-DOSMicrosoft Disk Operating System. The operating system thatcomes with your computer. See Operating system.Numeric keypadThe number keys grouped to the right of the keyboard.Operating speedThe speed at which the central processing unit can executecommands. Also called execution speed. The Apex can run at4.77 MHz or 10 MHz.operating systemA collection of programs (such as MS-DOS) that manages acomputer’s operations. The operating system determines howprograms run on the computer and supervises all input andoutput.Option cardA circuit board you install inside the computer to provideadditional capabilities, such as a modem, a hard disk controller,or a mouse.ParallelThe type of interface that transmits data in groups of bits. SeeInterface and Serial.ParameterA qualifier added to a command that tells the computer whatparticular conditions to look for.Parent directoryThe directory immediately above a given directory in thedirectory tree. In pathnames, the parent directory is representedby the symbol .. (two periods).Glossary 11
