Barrons Publishing Dictionary of Computer and Internet Terms 10th
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OASIS |
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O
OASIS (Organization for the Advancement of Structured Information Standards) an organization working on the development of e-business standards in areas such as web services (web address: www.oasisopen.org).
Ob- (slang) “obligatory”; used in newsgroup postings to signify a belated return to the intended topic. See TOPIC DRIFT.
obelisk the character †, a symbol used to mark footnotes. See also FOOTNOTE. Also called a DAGGER or LONG CROSS.
object
1. a data item that has procedures associated with it. See OBJECT-ORI-
ENTED PROGRAMMING.
2. one of the parts of a graphical image. See DRAW PROGRAM.
object code the output of a compiler; a program written in machine instructions recognizable to the CPU, rather than a programming language used by humans. Contrast
object linking and embedding (OLE) (in Microsoft Windows 3.1 and later versions) a method of combining information that is processed by different application programs, such as inserting a drawing or a portion of a spreadsheet into a word processing document. The main document is called the client and the document or application that supplies the embedded material is the server. OLE supersedes an older feature of Windows called dynamic data exchange (DDE).
OLE can be done in either of two ways. An embedded object becomes part of the document that it is inserted into. For example, if you embed a drawing into a word processing document, the whole thing becomes one file, and to edit it, you use the word processor, which will call up the drawing program when you double-click on the drawing to edit it. A linked object has a life of its own; it remains a separate file and can be edited separately. When you edit it, the information that is linked from it into other documents is automatically updated. Thus, you can use a word processor to create a report that has links to a spreadsheet, and when you update the information in the spreadsheet, the corresponding information in the report will be updated automatically. Embedding and linking correspond to “cold links” and “hot links” in Windows 3.0 DDE. See also ACTIVEX.
object-oriented graphics graphical images that are represented as instructions to draw particular objects, rather than as light or dark spots on a grid. See DRAW PROGRAM.
object-oriented programming a programming methodology in which the programmer can define not only data types, but also methods that are
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object-oriented programming |
automatically associated with them. A general type of an object is called a class. Once a class has been defined, specific instances of that class can be created.
The same name can be given to different procedures that do corresponding things to different types; this is called polymorphism. For example, there could be a “draw” procedure for circles and another for rectangles.
Some uses for object-oriented programming include the following:
1.Graphical objects. A program that manipulates lines, circles, rectangles, and the like can have a separate “draw” and “move” procedure for each of these types.
2.Mathematical objects. In order to work with vectors, matrices, or other special mathematical objects, the programmer has to define not only data structures for these objects, but also operations such as addition, inversion, or finding a determinant.
3.Input-output devices. The procedure to draw a line might be quite different on a printer or plotter than on the screen. Object-oriented programming provides a simple way to ensure that the right procedure is used on each device.
4.Simulation. In a program that simulates traffic flow, for example, cars, trucks, and buses might be types of objects, each with its own procedures for responding to red lights, obstructions in the road, and so forth. This, in fact, is what object-oriented programming was invented for. The first object-oriented programming language was Simula, introduced in 1967.
5.Reusable software components. Object-oriented programming provides a powerful way to build and use components out of which programs can be built. For example, a programmer might use a predefined object class such as “sorted list” (a list that automatically keeps itself in order) rather than having to write procedures to create and sort a list.
Here is an example of object-oriented programming in Java. Imagine a program that manipulates points, lines, and circles. A point consists of a location plus a procedure to display it (just draw a dot). So the programmer defines a class called pointtype as follows:
class pointtype
{
int x; int y;
void draw(Graphics g)
{
g.drawRect(x,y,1,1);
}
}
The class pointtype is defined to include two integer variables (x and y) and one method (draw). (The class also would include a CONSTRUC- TOR—a method called when a new object of that class is created.)
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Now variables of type pointtype can be declared, for example:
pointtype: a,b;
Here the objects a and b each contain an x and a y field; x and y are called instance variables. In addition, a and b are associated with the draw procedure. Here’s an example of how to use them:
a.x = 100; a.y = 150: a.draw(g);
This sets the x and y fields of a to 100 and 150, respectively, and then calls the draw procedure that is associated with a (namely pointtype.draw). (The g stands for graphics.)
Now let’s handle circles. A circle is like a point except that in addition to x and y, it has a diameter. Also, its draw method is different. We can define circletype as another type that includes a pointtype, and it adds an instance variable called diameter and substitutes a different draw method. Here’s how it’s done:
class circletype
{
pointtype p; int diameter;
void draw(Graphics g)
{
g.drawOval(p.x,p.y,diameter,diameter);
}
}
Your program would create a new object of class circletype (call it c), define values for the variables, and then call the method circletype.draw to display the circle on the screen.
It is important to remember that instance variables belong to individual objects such as a, b, and c, but methods (procedures) belong to object types (classes). One advantage of object-oriented programming is that it automatically associates the right procedures with each object: c.draw uses the circle draw procedure because object c is a circle, but a.draw uses the point draw procedure because object a is a point.
The act of calling one of an object’s methods is sometimes described as “sending a message” to the object (e.g., c.draw “sends a message” to c saying “draw yourself”). All object-oriented programming systems allow one class to inherit from another, so the properties of one class can automatically be used by another class. For example, there is a standard Java class called Applet which contains the code needed to display an applet on the web. When you write your own applet, it will inherit from (extend) this class, so you don’t need to recreate that code yourself. See also C++; C#; JAVA; SMALLTALK.
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off-by-one error |
OBO abbreviation for “or best offer,” often used when advertising things for sale on the Internet.
obscenity sexually explicit material that can be prohibited by law. In 1973 the Supreme Court of the United States ruled that material is obscene if the average person, using contemporary community standards, would find that its primary purpose is to stimulate sexual appetite (“the prurient interest”); it depicts sexual behavior defined as offensive by specific laws; and it “lacks serious, literary, artistic, political or scientific value” (Miller v. California). Contrast INDECENCY. See also COMPUTER LAW;
ICRA; PORNOGRAPHY.
OCR see OPTICAL CHARACTER RECOGNITION.
octal a way of writing numbers in base-8 notation. Octal numbers use only the digits 0, 1, 2, 3, 4, 5, 6, and 7, and the next column represents multiples of 8. For example, the octal number 23 means 2 eights and 3 ones, or 19. Here are some further examples:
Binary |
Octal |
|
|
Decimal |
||
001 |
000 |
10 |
1 |
× 81 = 8 |
|
|
001 |
001 |
11 |
1 |
× 81 + 1 |
= 9 |
|
001 |
010 |
12 |
1 |
× 81 + 2 |
= 10 |
|
010 |
001 |
21 |
2 |
× 81 |
+ 1 |
= 17 |
011 |
001 |
31 |
3 |
× 81 |
+ 1 |
= 25 |
100 |
001 |
41 |
4 |
× 81 |
+ 1 |
= 33 |
101 010 |
100 |
524 |
5 |
× 82 |
+ 2 |
× 81 + 4 = 340 |
Note that each octal digit corresponds to three binary digits.
octet a group of exactly eight bits, regardless of whether eight bits represent a character on any particular computer. Contrast BYTE.
octothorpe the character #; originally a map-maker’s representation of a village with eight fields (thorpes) around a central square. Also called a
POUND SIGN.
ODM (Original Design Manufacturer) a company that produces products for another firm that will sell them under its brand name.
OEM (Original Equipment Manufacturer) a company that assembles complete pieces of equipment from parts. In some Microsoft documentation, “OEM” is used as a euphemism for “IBM” in order to avoid naming the competitor directly; but it also refers to other manufacturers.
OEM character set the native character set of the IBM PC. For a chart, see IBM PC.
off-by-one error a programming error caused by doing something the wrong number of times (one time too many or one time too few); also called a FENCEPOST ERROR.
Office, Microsoft |
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Office, Microsoft suite of office applications including Word, Excel, Outlook, and PowerPoint. Microsoft markets specialized versions of Office for home or student use as well as a premium version that includes the database program Access. Details of the various collections vary as Microsoft’s marketing targets different users. Microsoft Office is the leading business application software used on microcomputers since the 1990s. Its main competitor is OPENOFFICE.ORG 2.
offset the distance, in a computer memory, between one location and another. The offset of a data item is its address relative to the address of something else (0 if they are in the same position, 5 if they are 5 bytes apart, and so forth).
offset printing a way of printing on paper by means of ink transferred by a rubber roller from another surface. Offset printing is a cheap way for a print shop to produce hundreds of copies of a laser-printed original.
Ogg Vorbis a format for encoding compressed digital audio that is non-pro- prietary, with better sound quality than MP3 format. For more information, see www.vorbis.com. Contrast MP3.
ohm the unit of measure of electrical resistance. If an object has a resistance of 1 ohm, then an applied voltage of 1 volt will cause a current of 1 ampere to flow. See OHM’S LAW.
Impedance is also measured in ohms. Impedance is similar to resistance but is defined in terms of alternating current rather than direct current. See IMPEDANCE.
Ohm’s law a basic law describing the behavior of electricity. It states that the current that flows through a circuit element is equal to the voltage applied across that element divided by the resistance of that element:
I = V/R
where I = current, in amperes; V = voltage, in volts; and R = resistance, in ohms. In effect, voltage is the force that drives a current through a resistance.
OLAP (Online Analytic Processing), performing analysis of multidimensional hierarchical data. An OLAP software tool will typically interact with data that is stored in a large database, but it provides more advanced techniques for processing and viewing the data than are provided by a database query language such as SQL. OLAP tools also provide more flexibility and power than do traditional spreadsheets.
A business typically will store data on a large number of individual transactions in a giant database. An OLAP tool will need to aggregate this data into a form that is useful for decisions. The data is inherently multidimensional, typically including dimensions for the time of the transaction, the location, the type of product, and a dimension for the type of variable (such as revenue, cost, and margin). Each dimension
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online trading |
typically has a hierarchy; for example, the time dimension is arranged by year/quarter/month/day; the location dimension can be arranged by country/state/city/store; and the product dimension is arranged into a hierarchy of categories.
To provide effective decision support, an OLAP tool should be able to generate views of the data quickly while supporting multiple users.
For an example of using a spreadsheet to view a limited form of multidimensional data, see PIVOT TABLE.
OLE see OBJECT LINKING AND EMBEDDING.
OLED (organic light-emitting diode) a type of light-emitting diode based on organic polymers instead of semiconductor crystals. See LED.
OLPC (One Laptop Per Child) a nonprofit organization providing inexpensive laptop computers to children in developing nations (web address: www.laptop.org).
OLTP abbreviation for on-line transaction processing.
OMG (Object Management Group) a consortium of hundreds of computer companies that develop standards for software components to interact with each other. See web address: www.omg.org. See also CORBA.
on-board included within a piece of equipment. For example, it is common for a motherboard to have an on-board Ethernet interface.
one-way function a function whose inverse is very hard to calculate. A function f is a one-way function if, given x, it is relatively easy to calculate y = f(x), but it is hard to calculate the inverse function (i.e., calculate the value of x if you are given the value of y). One-way functions are used in public key encryption schemes; see ENCRYPTION.
onionskin (animation software) a translucent drawing layer placed on top of a reference image for purposes of tracing, like onionskin paper.
online connected to a computer or available through a computer. For example, online help is information that can be called up immediately on a computer screen rather than having to be looked up in a book.
Usage note: Online is also written with a hyphen when used before a noun, as in on-line processing, or as two separate words when used predicatively, as in The computer is on line.
In New York City but not elsewhere, on line means “in a queue,” as in
We are standing on line—the rest of the country says standing in line. In this context it is not a computer term and is not written as a single word.
online casino, online gambling see GAMBLING.
online trading the buying and selling of stocks or other securities through the Internet. Instead of paying a broker to type transactions into a computer, you type them in yourself. Brokerage fees are much lower, and
OOBE |
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transactions are completed more promptly. Unfortunately, the broker’s wise counsel is absent, and fortunes have been lost through speculative day trading. See DAY TRADING.
OOBE see OUT-OF-BOX EXPERIENCE.
OOC abbreviation for “out of character,” used in role playing games and the like to indicate that a person’s comment is not part of the imaginary situation. Example: “OOC: That dragon reminds me that I need to feed my pet iguana.” See also IC; RPG (definition 1).
OOP see OBJECT-ORIENTED PROGRAMMING.
OPA (Open Patent Alliance) a group of companies formed in 2008 to promote development of WIMAX Internet use. Web address: www.openpatentalliance.com.
opacity (from opaque) inability to be seen through; the opposite of transparency. In a graphical image, objects with low opacity are partly transparent. Many special effects are implemented by creating a new image, with opacity under the control of the user, and superimposing it on the existing image. See also ALPHA CHANNEL.
open
1.to call a file, document, or drawing up from disk in order to work with it.
2.(in programming) to prepare a file to have data transferred into or out of it.
3.(in electronics) to put a switch into the position that does not allow current to flow.
open architecture a computer architecture whose details are fully made public so that other manufacturers can make clones and compatible accessories. The architecture of the original IBM PC is open; that of the original Macintosh is not.
open beta a test of incomplete software that is open to a very large group, often the entire public. See BETA TESTING.
open source software software whose source code is published so that a variety of people can add contributions. This is different from proprietary software such as Microsoft Windows, where the source code is a trade secret and only employees of the manufacturer work on the software’s development. Significant examples of open source software include the LINUX operating system, the APACHE web server, the OPENOFFICE.ORG 2 suite, and various GNU products.
open systems interconnection see DATA COMMUNICATION.
OpenOffice.org an OPEN-SOURCE office software suite whose functionality rivals the industry-leading Microsoft Office suite. OpenOffice comprises
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opt out |
programs for word processing, spreadsheets, presentations, graphics, and databases. It is maintained by a worldwide organization of programmers and contributors who provide the software free-of-charge. Some users report that the OpenOffice.org user interface isn’t as polished as its commercial rival, however user training and support is available at www.openoffice.org.
OpenType a format for type fonts on personal computers developed by Microsoft in the late 1990s as a combination of TrueType and Adobe Type 1. (See TRUETYPE; TYPE 1 FONT.) OpenType support is built into Windows 2000 and its successors.
Opera a popular independent web browser created by Opera Software (www.opera.com), using W3C standards. See BROWSER; FIREFOX; INTERNET EXPLORER.
operands the items on which a mathematical operation is performed. For example, in the expression 2 + 3, the operands are 2 and 3, and the operation is addition.
operating system a program that controls a computer and makes it possible for users to enter and run their own programs.
A completely unprogrammed computer is incapable of recognizing keystrokes on its keyboard or displaying messages on its screen. Most computers are therefore set up so that, when first turned on, they automatically begin running a small program supplied in read-only memory (ROM), or occasionally in another form (see BOOT). This program in turn enables the computer to load its operating system from disk, though some small microcomputers have complete operating systems in ROM.
Under the control of the operating system, the computer recognizes and obeys commands typed by the user. In addition, the operating system provides built-in routines that allow the user’s program to perform input-output operations without specifying the exact hardware configuration of the computer. A computer running under one operating system cannot run programs designed to be run under another operating system, even on the same computer. For articles on specific operating systems, see CMS; CP/M; LINUX; MAC OS; MS-DOS; MVS; OS/2; OS/360; UNIX; WINDOWS (MICROSOFT); Z/OS.
operations research the mathematical modeling of repetitive human activities, such as those involved in traffic flow, assembly lines, and military campaigns. Operations research makes extensive use of computer simulation.
opt out to choose not to receive mass e-mailings. When giving your e-mail address to an online merchant, look carefully for an opt-out CHECKBOX somewhere on the screen, and be sure to opt out of mailings you do not want to receive.
Many spammers falsely describe their mailing lists as opt-out lists; they ignore requests to opt out, because any reply tells them they have
optical character recognition |
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reached a good e-mail address. This is why it’s so important to never respond to spam. It’s like being hit on the head once and then asked whether you want to opt out from being hit again. See SPAM.
optical character recognition (OCR) the recognition of printed or handwritten characters in an image of a piece of paper. OCR software is commonly used with scanners so that information received on paper will not have to be retyped into the computer. A difficulty is that the computer usually cannot recognize letters and digits with complete certainty, so it has to make intelligent guesses based on the spellings of known words. For example, if you type “chack” an OCR device is likely to read it as “check.” Obviously, OCR has difficulty distinguishing l from 1 or O from 0; so do humans if they don’t know the context. Information obtained through OCR should be carefully checked for accuracy. See also SCANNER.
optical disc any kind of data storage disc that is read by means of light rays (visible, infrared, or ultraviolet). For examples see BLU-RAY DISC; CD; DVD.
optical disk a high-density storage device that stores information by etching tiny grooves in plastic with a laser. See CD-ROM and references there;
WORM.
optical zoom a change in the field view of a DIGITAL CAMERA achieved by changing the focal length of the lens. Unlike digital zoom, optical zoom does not sacrifice resolution (at least if the lens is of high quality).
Contrast DIGITAL ZOOM.
A lens marked “3× zoom” has a focal length that is three times as long at maximum as at minimum. See also FOCAL LENGTH.
option buttons small circles in a dialog box, only one of which can be chosen at a time. The chosen button is black and the others are white. Choosing any button with the mouse causes all the other buttons in the set to be cleared. Because option buttons work like the buttons on older car radios, they are sometimes called radio buttons.
FIGURE 183. Option buttons
Option key a key on the Macintosh keyboard labeled “Opt” that acts as another kind of Shift key, allowing special characters to be typed quickly. See also COMMAND KEY; MODIFIER KEY.
OR gate (Figure 184) a logic gate whose output is 1 when either or both of the inputs is 1, as shown in the table:
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|
orphan |
Inputs |
Output |
|
0 |
0 |
0 |
0 |
1 |
1 |
1 |
0 |
1 |
1 |
1 |
1 |
See also LOGIC CIRCUITS; COMPUTER ARCHITECTURE.
FIGURE 184. OR gate (logic symbol)
Oracle a leading producer of database software. Oracle Corporation is headquartered in Redwood Shores, California. Web address: www.oracle.com.
Orange Book
1.the official standard for compact discs that can be recorded by the user. See CD-ROM.
2.the U.S. government’s Trusted Computer System Evaluation Criteria, published in 1985 and defining standards for computer security.
ORB (Object Request Broker) a system that allows objects to connect to other objects over a network. See CORBA for a description of one set of standards that define how ORBs connect different components.
order of magnitude a factor-of-10 difference in size. If one number is 10 times larger than another, they differ by one order of magnitude. Personal computers have sped up by more than three orders of magni- tude—that is, a factor of more than 1,000—since the early days of the IBM PC.
More formally, the order of magnitude is the exponent in exponential notation. See
.org a suffix intended to indicate that a web or e-mail address belongs to a non-profit organization (in any country, but mostly the United States). Along with .com, .edu, .gov, .int, .net, and .mil, this is one of the original set of Internet top-level domains. Since 2000, .com, .net, and .org have been assigned almost indiscriminately to organizations of all types.
Contrast .COM. See also TLD; ICANN.
orphan
1.the last line of a paragraph if it appears by itself as the first line of a page. Some word processors automatically adjust page breaks to avoid creating orphans. See also WIDOW.
2.a computer product that is no longer supported by its manufacturer, or whose manufacturer is out of business. For example, the Amiga is now an orphan computer.