Object-oriented
Generally used to describe an illustration or font file as being created by mathematical equations. Also see Bit-map.

OCR
Optical Character Recognition. A technology that lets you scan a printed page (with a scanner) and convert it into text document that you can edit in a word processor.

Offset lithography
A high-volume, ink-based printing process, in which ink adhering to image areas of a lithographic plate is transferred (offset) to a blanket cylinder before being applied to paper or other substrate.

On-line
Actively connected to other computers or devices. You're on-line when you've logged on to a network, BBS, or on-line service. A device such as a printer is on-line when it's turned on and accessible to a computer. If you're not on-line then you're off-line.

On-line Service
A commercial service that (for a price) provides goodies such as e-mail, discussion forums, tech support, software libraries, news, weather reports, stock prices, plane reservations, even electronic shopping malls. To access one, you need a modem. Popular on-line services include America Online, CompuServe, and Prodigy.

Operating System
Software that supervises and controls tasks on a computer.

Optical Resolution
In the scanning context, this refers to the number of truly separate readings taken from an original within a given distance, as opposed to the subsequent increase in resolution (but not detail) created by software interpolation.

Optical Video Disc
Compact discs which use lights to read information.

OSI
Open Systems Interconnection, a set of standard protocol grouped into seven layers: the physical, data link, network, transport, session, presentation, and application layers.