Glossary: O

This page contains glossary terms beginning with the letter O.
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Word or Term Description or Explanation
Obey file a file of commands prepared for execution by the RISC OS command line interpreter
Object code the machine-executable code produced by a compiler
Object oriented the approach used in conventional programming is to have a number of procedures or routines which can work on some data - there is no conceptual connection between the data and the operations which are performed on it - in contrast to this, object-oriented programming works on a concept of objects, which consist both of data fields (similar to a structure in C) and of a list of methods which may be applied to that data - for example, you could define an object point (with data x and y, both integers), and define a move method on it to change these fields
one of the most useful concepts which may be derived from this is inheritance - an object can be defined as a sub-type of another object, and in doing so inherit all its methods (and data fields), but may also add its own - as an example, you could define a circle object with data x and y (inherited from the parent point object) but with another data field, radius - similarly, the circle would inherit the move method (which would not have to be rewritten), but could also have a resize method added to it
the result of these changes in approach is that it is often easier to implement large programs, since it is harder to get confused about how a piece of data should be used, and less code needs to be rewritten - object-oriented languages include Modula-3, C++ and Objective C
OCR Optical Character Recognition - computers can be trained to examine the shapes of typed or printed characters and work out what the letters, words and sentences are - so, combined with a scanner or camera and digitiser, the computer can 'read' text off books and paper - because of the difficulty of being 100% accurate, it may take as long to edit out the mistakes as to type the text in from scratch, so OCR programmers are fighting all the time to make their programs more and more accurate without becoming too slow for practical use - this facility will become more viable as we get progressively faster processors
Offline when your computer is not connected to a host system or the Net, you are offline
OLE Object Linking and Embedding - this is a means of linking data of different types (e.g. text, drawfiles, sprites, etc.) within one document so that each element can be easily edited - double-clicking on an element brings up the appropriate editing application (Draw, Paint, ArtWorks, etc) to allow you to make the necessary changes without having to export and then re-import the data
OLR Off-Line Reader - software used for reading email or Usenet news off-line
OMR Optical Mark Recognition - a system where when a sheet is passed through a scanner, the computer tells where the marks are and uses them to automatically fill out forms or similar - it means that forms can be filled out quickly by various people and fed into the computer which automatically sorts the data out according to the marks and programming - however, the system can reject a large number of forms as the system can not be very accurate - it depends on the person putting the marks on the paper
Online when your computer is connected to an online service, bulletin-board system or public-access site
Operating system this is the set of "house-keeping" programs within a computer which handle all the input/output, filing systems, etc. - all modern Acorn computers come with the RISC OS operating system as standard (stored in ROM) but it is possible to use alternative operating systems such as DR-DOS and MS-DOS by adding the appropriate software or hardware
Optical Mark
see OMR
Option icon an icon that appears in a dialogue box - each time you click on it, you will switch a particular option on or off
OS Operating System - see above
OS graphic unit a unit for defining graphics under RISC OS so that they are independent of the current screen mode - there are nominally 180 OS graphics units to the inch
OSCLI Operating System Command Line Interpreter - the part of the RISC OS operating system that deals with command lines that are either typed in at the keyboard or issued by other programs
Outline fonts these are fonts that are described mathematically by using equations to define the curves that make up the outline of the character's shape - using these equations, it is relatively simple to work out how to display any font at any size, either on the screen or on a printer where the shape has to be reproduced as a series of dots

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