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Glossary O
 In object-oriented programming (OOP), objects are the things you think about first in designing a program and they are also the units of code that are eventually derived from the process. In between, each object is made into a generic class of object and even more generic classes are defined so that objects can share models and reuse the class definitions in their code. Each object is an instance of a particular class or subclass with the class's own methods or procedures and data variables. An object is what actually runs in the computer.
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 Object-oriented programming (OOP) is a programming language model organized around "objects" rather than "actions" and data rather than logic. Historically, a program has been viewed as a logical procedure that takes input data, processes it, and produces output data. The programming challenge was seen as how to write the logic, not how to define the data. Object-oriented programming takes the view that what we really care about are the objects we want to manipulate rather than the logic required to manipulate them. Examples of objects range from human beings (described by name, address, and so forth) to buildings and floors (whose properties can be described and managed) down to the little widgets on your computer desktop (such as buttons and scroll bars).
The first step in OOP is to identify all the objects you want to manipulate and how they relate to each other, an exercise often known as data modeling. Once you've identified an object, you generalize it as a class of objects (think of Plato's concept of the "ideal" chair that stands for all chairs) and define the kind of data it contains and any logic sequences that can manipulate it. Each distinct logic sequence is known as a method. A real instance of a class is called (no surprise here) an "object" or, in some environments, an "instance of a class." The object or class instance is what you run in the computer. Its methods provide computer instructions and the class object characteristics provide relevant data. You communicate with objects - and they communicate with each other - with well-defined interfaces called messages.
The concepts and rules used in object-oriented programming provide these important benefits:
- The concept of a data class makes it possible to define subclasses of data objects that share some or all of the main class characteristics. Called inheritance, this property of OOP forces a more thorough data analysis, reduces development time, and ensures more accurate coding.
- Since a class defines only the data it needs to be concerned with, when an instance of that class (an object) is run, the code will not be able to accidentally access other program data. This characteristic of data hiding provides greater system security and avoids unintended data corruption.
- The definition of a class is reuseable not only by the program for which it is initially created but also by other object-oriented programs (and, for this reason, can be more easily distributed for use in networks).
- The concept of data classes allows a programmer to create any new data type that is not already defined in the language itself.
One of the first object-oriented computer languages was called Smalltalk. C++ and Java are the most popular object-oriented languages today. The Java programming language is designed especially for use in distributed applications on corporate networks and the Internet.
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 In relation to computer technology, "on the fly" describes activities that develop or occur dynamically rather than as the result of something that is statically predefined. For example, the content of a page that is sent to you from a Web site can be developed (and varied) "on the fly" based on dynamic factors such as the time of day, what pages the user has looked at previously, and specific user input. The Web server calls an application program to produce the "on-the-fly" page that is to be returned. There are several techniques for on-the-fly page development, including the server-side include, the use of cookie (information previously stored about you that is located in a special file on your hard disk), and Microsoft's Active Server Page.
In general usage, the expression often connotes a degree of haste and improvisation as in "I usually grab breakfast on the fly." This usage is somewhat similar to the expression "catch as catch can." The term also can simply connote being in a mobile or fluid situation. Our Webster's New World Dictionary reminds us that the term probably originated with bird hunting and shooting birds on the fly (rather than on the ground). The dictionary says simply ""in flight" and adds a colloquial meaning of "in a hurry."
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 Open Source is a certification mark owned by the Open Source Initiative (OSI). Developers of software that is intended to be freely shared and possibly improved and redistributed by others can use the Open Source trademark if their distribution terms conform to the OSI's Open Source Definition. To summarize, the Definition model of distribution terms require that:
- The software being distributed must be redistributed to anyone else without any restriction
- The source code must be made available (so that the receiving party will be able to improve or modify it)
- The license can require improved versions of the software to carry a different name or version from the original software
The idea is very similar to that behind free software and the copyleft concept of the Free Software Foundation. Open Source is the result of a long-time movement toward software that is developed and improved by a group of volunteers cooperating together on a network. Many parts of the Unix operating system were developed this way, including today's most popular version, Linux. Linux uses applications from the GNU project, which was guided by Richard Stallman and the Free Software Foundation. The Open Source Definition, spearheaded by Eric Raymond (editor of The New Hacker's Dictionary), is an effort to provide a branded model or guideline for this kind of software distribution and redistribution. The OSI considers the existing software distribution licenses used by GNU, BSD (a widely-distributed version of UNIX), X Window System, and Artistic to be conformant with the Open Source Definition.
Prior to its acquisition by AOL, Netscape, in an effort to stay viable in its browser competition with Microsoft, made its browser source code (codenamed Mozilla) freely available, encouraging hacker to improve it. Possible enhancements will presumably be incorporated into future versions. The open source movement has gained momentum as commercial enterprises have begun to consider Linux as an open alternative to Windows operating systems.
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 The purpose of a one-time password (OTP) is to make it more difficult to gain unauthorized access to restricted resources, like a computer account. Traditionally static passwords can more easily be accessed by an unauthorized intruder given enough attempts and time. By constantly altering the password, as is done with a one-time password, this risk can be greatly reduced.
There are basically three types of one-time passwords: the first type uses a mathematical algorithm to generate a new password based on the previous, a second type that is based on time-synchronization between the authentication server and the client providing the password, and a third type that is again using a mathematical algorithm, but the new password is based on a challenge (e.g. a random number chosen by the authentication server or transaction details) and a counter instead of being based on the previous password.
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 OpenGL (Open Graphics Library) is the computer industry's standard application program interface (API) for defining 2-D and 3-D graphic images. Prior to OpenGL, any company developing a graphical application typically had to rewrite the graphics part of it for each Operating system platform and had to be cognizant of the graphics hardware as well. With OpenGL, an application can create the same effects in any operating system using any OpenGL-adhering graphics adapter.
OpenGL specifies a set of "commands" or immediately executed functions. Each command directs a drawing action or causes special effects. A list of these commands can be created for repetitive effects. OpenGL is independent of the windowing characteristics of each operating system, but provides special "glue" routines for each operating system that enable OpenGL to work in that system's windowing environment. OpenGL comes with a large number of built-in capabilities requestable through the API. These include hidden surface removal, alpha blending (transparency), antialiasing, texture mapping, pixel operations, viewing and modeling transformations, and atmospheric effects (fog, smoke, and haze).
Silicon Graphics, makers of advanced graphics workstations, initiated the development of OpenGL. Other companies on the industry-wide Architecture Review Board include DEC, Intel, IBM, Microsoft, and Sun Microsystems. There is no cost (other than learning) to developing an application using the OpenGL API. Microsoft offers free downloads of the OpenGL libraries for its Windows systems. Although OpenGL is not itself a development "toolkit," such toolkits are available, including Silicon Graphics object-oriented programming 3D graphics toolkit, Open Inventor.
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 Opera is a Web browser that provides some advantages over other browsers from Mozilla or Microsoft. Much smaller in size, Opera is known for being fast and stable. Opera is available for a number of operating systems, including BeOS, Symbian OS, Linux, Mac OS, OS/2, Solaris, and Windows. It offers the same capabilities of the more popular browsers including integrated searches and instant messaging, support for JavaScript, cascading style sheets and e-mail. Because Opera is so compact, it has been promoted for use in hand-held Internet devices.
Opera is free for download to all supported platforms. The free version of Opera contains ads, which are cached weekly to insure Opera's fast speed is maintained. The other versions of Opera do not have ads, which is why Opera charges a modest one-time license fee.
The feature you notice first after installing Opera is a menu or "hotlist" that serves as both a directory to the Web and a bookmark file. The hotlist can be easily removed and you can use the full viewing space to look at multiple Web sites at the same time, either tiling or cascading the windows. You can choose to have the sites you were last looking at restored the next time you open the Opera browser. Opera offers keyboard as well as mouse control of its features. Plug-ins such as RealAudio, RealVideo, and Shockwave can be added. Opera does not support Active-X or Visual Basic.
Opera began in 1994 as a research project for the national phone company in Norway. It is now on its 9th version.
Other Web browsers include Firefox, Internet Explorer, Apple Computer's Safari and Mosaic, developed in 1993 and the original code base for Netscape's browser, Lynx.
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 An operating system (sometimes abbreviated as "OS") is the program that, after being initially loaded into the computer by a boot program, manages all the other programs in a computer. The other programs are called applications or application programs. The application programs make use of the operating system by making requests for services through a defined application program interface (API). In addition, users can interact directly with the operating system through a user interface such as a command language or a graphical user interface (GUI).
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 OS/2 is an IBM Operating system for the personal computer that, when introduced in 1987, was intended to provide an alternative to Microsoft Windows for both enterprise and personal PC users. The last version of OS/2 Warp, Warp 4, offered a Netscape-based Web browser that exploited OS/2's speech recognition capability. IBM enhanced OS/2 to provide server functions for e-business.
While OS/2 is still in use, IBM has announced that its support will require a special contract beginning in 2006.
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 Outlook Web Access (OWA) is a webmail service of Microsoft Exchange Server 5.0 and later, originally called Exchange Web Connect (EWC). The web interface of Outlook Web Access resembles of the interface in Microsoft Outlook. Outlook Web Access comes as a part of Microsoft Exchange Server 2007 and previous versions of Exchange.
OWA is used to access e-mail (including support for S/MIME), calendars, contacts, tasks, and other mailbox contents when not having access to Outlook. In the Exchange 2007 release, OWA also offers read-only access to documents stored in Microsoft SharePoint sites and network (UNC) shares. Microsoft provides Outlook Web Access as part of Exchange Server to allow users to connect remotely via a Web browser. Some of the functionality in Microsoft Outlook is also available in this web "look-alike". The most important difference is that Microsoft Outlook lets you work with e-mail, calendars etc. even when you don't have a network connection, while OWA requires a network connection to function.
OWA can be used from Internet cafes and any other location that provides connectivity to the Web. The OWA interface available in Exchange 2000, Exchange 2003, and Exchange 2007 is available in two flavors. The "Premium" UI is rendered for Internet Explorer 5 (for the 2000 and 2003 releases) and Internet Explorer 6SP1 and later for the 2007 release. The "Basic" UI is rendered for other browsers.
The first component to allow client-side script to issue HTTP requests (XMLHTTP) was originally written by the Outlook Web Access team. It soon became a part of Internet Explorer 5.0. Renamed XmlHttpRequest and standardised by international bodies, it has since become one of the cornerstones of the Ajax technology used to build advanced web applications today (2006).
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