Dictionary of Computer and Internet Terms phần 7 docx

FIGURE 178. Newspaper columns newsreader a piece of software that enables the user to read Usenet news- groups. See NEWSGROUP. NFS (Network File System) a FILE SHARING protocol originally developed by Sun Microsystems in the mid-1980s and now widely used on UNIX- based systems. Compare CIFS. NIB (describing items for sale) “new, in box.” nibble a group of 4 bits, or half of 1 byte. NIC (Network Interface Card) the circuit board inside a computer that con- nects it to a local-area network. nicad, NiCd (nickel-cadmium) a type of rechargeable battery formerly used in laptop computers. Nickel-cadmium batteries are toxic and should not be discarded in ordinary trash. See also LI-ION; NIMH; ROHS. Nigerian scam see 419 SCAM. NiMH (Nickel-Metal Hydride) a type of rechargeable battery electrically similar to nickel-cadmium (NICAD) but having greater capacity. See also LI-ION. nm see NANOMETER. node 1. an individual computer (or occasionally another type of machine) in a network. 2. a connection point in a data structure such as a linked list or tree. 3. (draw programs) a point on a curve or line that helps define the shape of the line. See CUSP NODE; SMOOTH NODE; SPLINE. non-breaking hyphen a hyphen that does not indicate a place where a word can be broken apart. For instance, if the hyphenated word “flip- flop” falls at the end of the line, then “flip-” can appear on one line, with “flop” at the beginning of the next. But if you type “flip-flop” with a required hyphen, it will not be split up. In Microsoft Word, to type a non- breaking hyphen press Ctrl-Shift and the hyphen key together. non-breaking space a space that does not denote a place where words can be split apart at the end of a line. For instance, you might not want a per- son’s initials (as in “T. S. Eliot”) to be split at the end of a line. You should 331 non-breaking space 7_4105_DO_CompInternetTerms_N 12/29/08 10:31 AM Page 331 therefore use required spaces between them rather than ordinary spaces. In T E X, a required space is typed as ~ (TILDE). In Microsoft Word, a non- breaking space is typed by pressing Ctrl-Shift and the space bar together. non-volatile not erased when turned off. Disks are a non-volatile storage medium; memory (RAM) is volatile. nondocument mode a type of word processing that produces plain-text (ASCII) files with no special codes for hyphenation, page breaks, fonts, or the like. The most common way of saving a file in nondocument mode is to use the “Save as” menu and choose “text file” or “text only.” See TEXT FILE. NOR gate (Figure 179) a logic gate whose output is 0 when either or both of the two inputs is 1, thus: Inputs Output 00 1 01 0 10 0 11 0 A NOR gate is equivalent to an OR gate followed by a NOT gate. NOR gates are important because all the other types of logic circuits can be built from them. See LOGIC CIRCUITS. FIGURE 179. NOR gate (logic symbol) Norton Utilities a set of programs originally written by Peter Norton and now a product of Symantec Corporation, used to provide security, recover erased files, and correct other problems with disks. See RECOV- ERING ERASED FILES. Web address: www.symantec.com/norton. NOS 1. (Network Operating System) any special operating system or operat- ing system extension that supports networking. 2. (New Old Stock) old but never sold to a customer and still in origi- nal packaging; this describes parts for obsolete equipment or the like. Compare LNIB. NOT gate (Figure 180) a logic gate whose output is 1 if the input is 0, and vice versa, thus: Inputs Output 01 10 non-volatile 332 7_4105_DO_CompInternetTerms_N 12/29/08 10:31 AM Page 332 A NOT gate is also called an inverter because it reverses the value of its input. See LOGIC CIRCUITS. FIGURE 180. NOT gate (inverter) notebook a computer about the same size as a looseleaf notebook, weigh- ing less than 6 pounds (2.7 kg). Usage note: The distinction between “laptop” and “notebook” has become blurred; all present-day laptop computers are notebooks by the standards of a few years ago. Many people use “laptop” and “notebook” interchangeably. NP-complete problem see LIMITS OF COMPUTER POWER. NPC non-player character, a (simulated) person in an online game who is not controlled by a player. NPN one of the two types of bipolar TRANSISTORs (contrast PNP). NRFB (describing items for sale) “never removed from box.” See also EBAY; MIB. NSFW Not Safe For Work, a warning sometimes given on an online forum when the upcoming content isn’t appropriate for a work environment. NSI see NETWORK SOLUTIONS, INC. NT short for Windows NT. See WINDOWS (MICROSOFT). NTFS the file system used by Windows NT and its successors. Contrast CDFS; FAT; WINDOWS (MICROSOFT). NTSC (National Television System Committee) the type of analog color TV signal used in the United States. It was designed to be compatible with a pre-existing black-and-white system. The screen consists of 525 lines, interlaced, and a complete scan takes 1/30 second. Color informa- tion is modulated on a 3.58-MHz subcarrier. Regulations mandated the end of NTSC broadcasting in February 2009, but NTSC video signals will continue to be used in low-cost analog video monitors and the like. Contrast DIGITAL TELEVISION; HDTV; PA L; SECAM. .nu suffix indicating that an e-mail or web address is registered on Niue Island in the South Pacific. Niue Island has resold most of its domain addresses for use elsewhere. See TLD. nudge to move a selected object in small increments by using the arrow keys instead of the mouse. 333 nudge 7_4105_DO_CompInternetTerms_N 12/29/08 10:31 AM Page 333 null-terminated string a CHARACTER STRING that ends with ASCII code 0. Null-terminated strings are used in the C programming language and in many of the system routines of UNIX and Windows. Num Lock a key on PC-compatible computers that switches the NUMERIC KEYPAD between two functions: typing numbers or moving the cursor with arrow keys. number crunching (slang) arithmetical calculation, especially for scien- tific or engineering purposes. numeric keypad a separate set of keys at the end of the keyboard, con- taining the digits 0 to 9 and a decimal point key. The digits are arranged in the same way as they are on an adding machine. If you have to type large quantities of numeric data, a numeric keypad is quicker to use than the number keys on the regular keypad. Some people prefer a keyboard without a numeric keypad because it lets them place the mouse closer to where they sit. See also KEYBOARD. numerical integration the process of finding the area under a particular curve by dividing the area into many tiny rectangles, adding up the heights of individual rectangles, and then multiplying the sum by their common width. See Figure 181. Numerical integration is a good exam- ple of a calculation that is practical to do on a computer but not by hand. FIGURE 181. Numerical integration For example, in probability theory it is important to find the area under the bell curve defined by: y = e –x 2 /2 This area can be found with the program in Figure 182, which uses a loop to perform a numerical integration. As you might imagine, it would 1 2π null-terminated string 334 7_4105_DO_CompInternetTerms_N 12/29/08 10:31 AM Page 334 take a long time to perform this calculation with a calculator, and it would be entirely impractical to do it by hand. NVIDIA a major manufacturer of graphics processors for personal com- puters, located in Santa Clara, California (www.nvidia.com). The name appears to be a pun on the Latin invidia “envy” although it is usually defined as n for numeric plus video. NVRAM (non-volatile random-access memory) the memory in which infor- mation about a computer’s configuration is stored; it is either powered by a battery or inherently able to retain data when power is off. Compare CMOS RAM, which is an older term. See also EEPROM; FLASH MEMORY. class numerical_integration { /* This Java program finds the area under the standard normal probability curve between x=0 and x=b, which is 1.0 in this example */ public static void main(String args[]) { double b=1.0; double a=0; double p=Math.sqrt(2*Math.PI); double dx=1/100.0; for (double x=dx; x<b; x+=dx) { double y = Math.exp(-x*x/2); a += y; } double area=a*dx/p; System.out.println( ”Area =” + area); } } FIGURE 182. Numerical integration algorithm 335 NVRAM 7_4105_DO_CompInternetTerms_N 12/29/08 10:31 AM Page 335 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.oasis- open.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 FOOT- NOTE. 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 instruc- tions recognizable to the CPU, rather than a programming language used by humans. Contrast SOURCE CODE. 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 informa- tion 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 instruc- tions 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 OASIS 336 7_4105_DO_CompInternetTerms_O 12/29/08 10:33 AM Page 336 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 corre- sponding 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, rec- tangles, and the like can have a separate “draw” and “move” pro- cedure 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 pro- cedure 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 automati- cally 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.) 337 object-oriented programming 7_4105_DO_CompInternetTerms_O 12/29/08 10:33 AM Page 337 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 pro- cedure. 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 addi- tion 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 individ- ual 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. object-oriented programming 338 7_4105_DO_CompInternetTerms_O 12/29/08 10:33 AM Page 338 339 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 pruri- ent 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 mul- tiples 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 × 8 1 = 8 001 001 11 1 × 8 1 + 1 = 9 001 010 12 1 × 8 1 + 2 = 10 010 001 21 2 × 8 1 + 1 = 17 011 001 31 3 × 8 1 + 1 = 25 100 001 41 4 × 8 1 + 1 = 33 101 010 100 524 5 × 8 2 + 2 × 8 1 + 4 = 340 Note that each octal digit corresponds to three binary digits. octet a group of exactly eight bits, regardless of whether eight bits repre- sent 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 com- plete 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. 7_4105_DO_CompInternetTerms_O 12/29/08 10:33 AM Page 339 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 informa- tion, see www.vorbis.com. Contrast MP3. ohm the unit of measure of electrical resistance. If an object has a resis- tance 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 resis- tance but is defined in terms of alternating current rather than direct cur- rent. 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 multidimen- sional 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 Office, Microsoft 340 7_4105_DO_CompInternetTerms_O 12/29/08 10:33 AM Page 340 [...]... 594 × 841 420 × 594 2 97 × 420 210 × 2 97 148 × 210 105 × 148 33.1 × 46.8 23.4 × 33.1 16.5 × 23.4 11 .7 × 16.5 8.3 × 11 .7 5.8 × 8.3 4.1 × 5.8 B0 B1 B2 B3 B4 B5 1000 × 1414 70 7 × 1000 500 × 70 7 353 × 500 250 × 353 176 × 250 39.4 × 55 .7 27. 8 × 39.4 19 .7 × 27. 8 13.9 × 19 .7 9.8 × 13.9 6.9 × 9.8 paper sizes (ISO) a set of standard sizes of paper used everywhere except the United States, of which A4 is the best... (describing a software license) assigned to a specific computer or set of computers Most software is licensed per computer; that is, the license gives you the right to install each copy on one computer for the use of anyone who wants to use it there Contrast PER SEAT, PER USER 7_ 4105_DO_CompInternetTerms_P 12/29/08 10:34 AM Page 361 361 Perl per device (describing a computer license) PER COMPUTER per... overcomes the problem 7_ 4105_DO_CompInternetTerms_P 3 57 12/29/08 10:34 AM Page 3 57 patch To select passive FTP, type the command passive in a command-line FTP session, or make the appropriate choice in setting up your FTP client software For example, in Microsoft Internet Explorer, passive FTP is an option under Tools, Internet Options, Advanced passive matrix an older type of liquid crystal display... 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 7_ 4105_DO_CompInternetTerms_O 343 12/29/08 10:33 AM Page 343 opt out programs for word processing, spreadsheets, presentations, graphics, and databases... analysis, by computer, of the structure of statements in a human or artificial language For instance, Windows has to parse the command dir b: /p to determine that dir is the name of the command, b: specifies the files to be shown, and p is another parameter (in this case, it means “pause when the screen is full”) Compilers and interpreters have to parse statements in 7_ 4105_DO_CompInternetTerms_P 12/29/08... 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... EXPRESSCARD and note there PC compatibility the ability of a computer to run the same programs and use the same hardware accessories as the original IBM Personal Computer (PC) or newer computers of the same general type In order to be fully PC-compatible, a computer needs an 8088-family processor (which nowadays means a Pentium or equivalent) Some other computers can software-emulate a Pentium and thereby... 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... radio transmitter that is allowed to operate without a license under the terms of Part 15 of the Federal Communications Commission’s regulations (known to lawyers as 47 CFR 15) Examples 7_ 4105_DO_CompInternetTerms_P 355 12/29/08 10:34 AM Page 355 Pascal include cordless telephones, wireless intercoms, and some kinds of wireless computer communication devices (wireless LANs) Because individual Part 15... (definition 1) 7_ 4105_DO_CompInternetTerms_O 12/29/08 10:33 AM 3 47 Page 3 47 overflow 2 a way of representing the main points of a text without giving all the details People have been making outlines on paper for centuries, but a computer can simplify the process in two ways First, with a word processor, it is easy to create a document by first typing an outline of it, and then going back and filling in the sections . FENCEPOST ERROR. 7_ 4105_DO_CompInternetTerms_O 12/29/08 10:33 AM Page 339 Office, Microsoft suite of office applications including Word, Excel, Outlook, and PowerPoint. Microsoft markets specialized. 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 Office, Microsoft 340 7_ 4105_DO_CompInternetTerms_O. 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,