Barrons Publishing Dictionary of Computer and Internet Terms 10th

typesetting mistakes

496

4. Novelty typefaces such as Zapf Chancery. These should be used very sparingly to make dramatic-looking titles or mastheads.

See also DESKTOP PUBLISHING; FONT; LEADING; PITCH; POINT; SERIF.

Times Roman

ABCDEF abcdefghijklmnopqrstuvwxyz 1234567890 @#$%&*( ).,:;!?

Helvetica

ABCDEF abcdefghijklmnopqrstuvwxyz 1234567890 @#$%&*( ).,:;!?

Courier

ABCDEF abcdefghijklmnopqrstuvwxyz 1234567890 @#$%&*( ).,:;!?

Apple Chancery

ABCDEF abcdefghijklmnopqrstuvwxyz 1234567890 @#$%&* .,:;!?

FIGURE 278. Typefaces

typesetting mistakes common errors in the use of type on computers, arising because most computer users do not know the practices of the printing industry. The following pointers will help you avoid blunders:

•Notice the differences between typesetting and typing on a typewriter:

–opening and closing quotation marks are different characters (“like this”);

–a dash (—) is not the same as two hyphens (--);

–underlining is rarely used—where you would underline on a typewriter, use italics (or possibly boldface) in type.

•Your type is proportionally spaced; letters are not all the same width. You can’t count letter spaces the way you do on a typewriter; you must use other means of aligning. Always align columns with the Tab key, not the space bar.

•Type carefully. Be sure not to hit the space bar more than once between words. It’s hard to tell the difference between one space and two spaces by just looking at the screen.

•Don’t justify everything. Justified type looks good only when the columns are wide enough. Flush-left type with a ragged right margin is easier to read if the columns are narrow; with narrow columns, justification puts excessive space between words. See JUS-

TIFICATION; RIVER.

497	typesetting mistakes

•Don’t use more than one or at most two fonts in a document (italics, boldface, and different sizes count as a single font). Multiplefont documents are almost always ugly. Odd typefaces (such as Old English) are very hard to read.

•Make sure your document is not missing any essential features such as adequate margins or page numbers. If in doubt, find a welldesigned document or book and imitate it.

•Use appropriate features of your software. When you type a footnote, use the footnote instruction if there is one, rather than just moving the cursor to the foot of the page. That way, if you change the layout later, the software will probably still handle the footnote correctly.

•Standardize. Don’t face each document as an original design problem. Develop a standard format that you like, and stick with it.

u

498

U

u typewritten representation for the Greek letter µ (mu), abbreviation for micro- (1/1,000,000). For abbreviations that begin with µ, see page 5.

ubiquitous in use everywhere. For example, “ubiquitous web protocols” are protocols such as HTTP and FTP that are available to practically all computer users. See PROTOCOL.

Ubuntu a Linux distribution based on Debian, with even easier installation and greater interoperability with Microsoft Windows. Ubuntu is highly recommended for Windows/Linux dual-boot systems.

Ubuntu was originated by South African entrepreneur Mark Shuttleworth. Its name is Zulu for “humanitarianism.” For more information, or to download Ubuntu, see www.ubuntu.com. See also DEBIAN;

LINUX.

uC (more properly µC, where µ is the Greek letter mu) abbreviation for

MICROCONTROLLER.

UCM (Use Case Maps) a visual representation of the requirements of a system, using a precisely defined set of symbols for responsibilities, system components, and sequences. UCMs have been applied to the development of telecommunications and other complex systems.

UCMs can be created with a free software tool (Use Case Maps Navigator, available at www.usecasemaps.org/tools/ucmnav) which ensures that the UCM has the correct syntax and also can be used to generate an XML listing of the system requirements. See also USE CASES.

UDDI (Universal Description, Discovery and Integration) a framework for describing WEB SERVICES so other Internet users can find them. See www.uddi.org.

UDDRP, UDRP (Uniform Domain Name Dispute Resolution Policy) a process established by ICANN to allow trademark holders to wrest control of domain names away from domain name poachers. An arbitration panel decides if the domain name holder obtained the domain name in bad faith to violate a trademark.

UI see USER INTERFACE.

.uk suffix indicating that an e-mail or web address is registered in the United Kingdom (England, Scotland, Wales, and Northern Ireland).

See TLD.

UL HTML tag that indicates an unnumbered list. For an example, see HTML.

U/lc (upper and lowercase) MIXED CASE. Also written c/lc (caps and lowercase). U/lc is the normal method of setting type. Contrast CAPS.

ulimitcheck see LIMITCHECK.

499

UML

ULV Ultra Low Voltage.

UML (Unified Modeling Language) a language used for the visual representation of software systems (and other types of systems). Much of UML was developed at Rational Software, and it was adopted as a standard by the Object Management Group (OMG) in 1997. UML includes standard notation for representing classes and their attributes and associations, and it includes state transition, interaction, component, and deployment diagrams.

Figure 279 shows an example of a UML class diagram for a program that keeps track of the movement of boats. Each class is enclosed in a rectangle, with the name of the class at the top. The middle part of the rectangle lists attributes (or variables) for the members of that class.

FIGURE 279. UML class diagram

For example, boats have a name represented as a string, x and y position coordinates and vx and vy velocity components, all of which are double-precision numbers. The bottom part of the class lists the operations (or methods) of that class.

In this example, two specific types of boats (sailboats and motorboats) inherit from the class Boat. Inheritance is indicated by an open arrow. Another class is the wind. The line connecting the wind and sailboat class indicates an interaction between those two classes since the operation that sets the velocity of the sailboat needs to know the wind direction and speed.

Figure 280 shows an example of a UML deployment diagram for a three-tier system where customers use a browser to connect over the Internet to the web server. The web server is, in turn, connected to the corporate mainframe database.

UML is designed for the development of complicated systems, so a complete design will include many different UML diagrams. UML diagrams can be created by hand or with a specialized software drawing tool.

unboxing

500

FIGURE 280. UML deployment diagram

unboxing (in Microsoft .NET Framework) the opposite of BOXING; the automatic conversion of simple objects back into value types, such as numbers and structs, after an operation for which BOXING was needed.

UNC (Uniform Naming Convention) the standard way of identifying shared resources (disks, directories, or printers) on Microsoft networks. UNC names have the form

\\computer\resource

or

\\computer\resource\path

For example, if computer zeta shares its drive C under the name cdrive, then file c:\MyDoc\letter.doc on that machine is accessible through the network as

\\zeta\cdrive\MyDoc\letter.doc.

Under Windows 2000 and later versions, URLs (Uniform Resource Locators) can be used as an alternative to UNC paths. The example just given would be file://zeta/cdrive/MyDoc/letter.doc in URL form.

underflow in computation, a situation that arises when a number is too small to be represented in the chosen format; it may then be incorrectly represented as 0.

For example, on an 8-digit fixed-point calculator, the computation 1÷1,000,000,000 would cause an underflow because the result, 0.000000001, could not be distinguished from zero.

On most computers, that particular computation would not cause a problem, since computers normally use a binary form of EXPONENTIAL

NOTATION, but there are limits on the size of the exponent; for example, a computer might not be able to represent 2–1024 because the exponent

would have too many binary digits. Compare OVERFLOW.

underrun an unexpected lack of data. When recording a CD-R or DVD-R, the drive must run at a fixed speed throughout the recording process. If the computer cannot deliver data to it fast enough—because of a network problem or because the data is coming from a slower device—an underrun occurs, and the disc is not recorded successfully. The cure is to make sure no other software is running, record at a lower speed, and, if necessary, temporarily take the computer off the network.

501

Unicode

undo a command that allows the computer user to reverse the effects of the most recent operation. If “Undo” is DIMMED (printed in gray), it is not possible for your program to undo a command (perhaps you have performed an intermediate step—or perhaps the most recent command was a complex operation that cannot be undone). For this reason, it is wise to save different versions of the file as you work so that you will have a recent version to REVERT to in case of disaster. See also REDO.

undocumented not described in the literature (documentation) provided by the manufacturer of a product.

Some computer programs rely on undocumented features of the machine on which they run. The risk of using undocumented features is that they may not be the same in future versions of the program or machine.

Undocumented features exist for several reasons. Some are accidental omissions from the documentation. Others represent incompletely tested features that will be made reliable and documented in future versions. Still others may be kept secret in order to give the vendor a competitive advantage in making add-on products. See also DOCUMENTATION.

unerase see RECOVERING ERASED FILES.

ungroup (in vector graphics) to cause a grouped object to be broken down into its component objects. It is necessary to ungroup to change the attributes of a single object or to change its shape.

unhandled exception an error condition, such as inability to write on a file, that was detected while running a program that provided no specific way of handling it. This is a common error message in the .NET Framework, and if the cause is not obvious, it reflects a programmer’s error. See EXCEPTION; .NET FRAMEWORK.

Unicode a system for representing characters using up to 20 bits, allowing for 1,048,576 different characters, enough to represent all the written languages of the world, including Japanese and Chinese. This contrasts with the 256 characters possible in ASCII and similar systems.

The Unicode standard is not yet complete. Originally, Unicode characters were 16 bits, as in the UTF-16 format described later, and only 65,536 characters were possible. Unicode version 3 goes beyond this limit and defines over 90,000 characters. Complete information is available at www.unicode.org.

The first 128 Unicode character codes are the same as ASCII, including end-of-line marks (see CR, LF). In various programming languages and editors, Unicode character codes are written as U+XXXX or \uXXXX, where XXXX stands for a series of hexadecimal digits; thus, the letter A, ASCII hexadecimal 41, is Unicode U+0041. Figure 281 shows examples of Unicode characters.

There are several kinds of Unicode text files. The most important are:

•UTF-8—Same as ASCII for codes up to 127; thus, a UTF-8 file can also be an ASCII file. Higher-numbered codes are represented by sequences of up to 4 bytes.

uniform fill

502

•UTF-16 big-endian—Each character occupies 2 bytes (16 bits), high-order byte first. The file begins with hexadecimal FE FF or with any Unicode character. Codes higher than 16 bits are represented by pairs of 16-bit sequences.

•UTF-16 little-endian—Just like UTF-16 big-endian, except that each pair of bytes has the low-order byte first, and the file begins with hexadecimal FF FE (representing the value FEFF). This is the Unicode system normally used in Microsoft Windows.

Unicode is used internally by the Java programming language and many newer software packages. However, the characters that you will actually see on your machine are limited by the fonts installed.

Hint: When you open a UTF-16 file in an ASCII text editor on a PC, you generally see characters separated by blanks (“l i k e t h i s”—the blanks are really ASCII 0). The remedy is to use a Unicode editor, such as Windows Notepad, and save the file as ASCII.

See also ANSI; ASCII; BIG-ENDIAN; CHARACTER SET; LITTLE-ENDIAN.

Character	ASCII	Unicode
$	hex 24	U+0024
A	hex 41	U+0040
π	none	U+03C0

none U+05D0

FIGURE 281. Unicode characters

uniform fill one solid color or tint that fills a graphical object. Contrast

FOUNTAIN FILL.

FIGURE 282. Uniform fill

uninitialized variable a VARIABLE in a computer program that has not been given a value. It contains random data depending on its exact location in memory and the programs that have run previously. Commonly, a program containing this kind of error will run correctly most of the time (when the variable happens to contain a reasonable value) but will fail at unpredictable times.

Some compilers automatically initialize all variables to zero or signal an error when an uninitialized variable is used. See INITIALIZE (definition 1).

uninterruptible power supply (UPS) a power supply that uses batteries to continue providing electricity to a computer for a few minutes in the event of a power failure. This makes it possible to shut down the computer in an orderly way without losing data.

503

UNIX

A UPS is not the same as a SURGE PROTECTOR. The surge protector absorbs momentary (millisecond-long) spikes of excess voltage; the UPS protects against the absence of voltage for minutes or hours. Most UPSes include surge protection, but not vice versa.

The batteries in a UPS deteriorate with age. A UPS that has been in use for two or three years generally has much less capacity than when it was new.

Usage note: The spelling uninterruptable is also widely used. Both spellings, with -ible and -able, are consistent with the word’s Latin etymology.

union a data item that can hold values of more than one type. See VARIANT.

uniprocessor free see FREE.

universal serial bus see USB.

UNIX an operating system, or family of operating systems, developed at Bell Laboratories in the early 1970s as a replacement for an earlier system called Multics. UNIX is noteworthy because, although developed by a small team of about four people, it is in many ways superior to operating systems developed by large teams at tremendous expense (e.g., OS/360). The current version of the Macintosh operating system (MAC OS X) is based on UNIX, as is LINUX.

The main features of UNIX include the following:

1.Highly modular, structured design. The entire system is defined in terms of a relatively small number of subroutines; UNIX can be implemented on any machine by implementing those routines. Furthermore, the operation of the whole system is based on a relatively small number of principles carried through very consistently; there is little arbitrary detail for the user to learn.

2.Extensibility. In many operating systems, users can create commands of their own that execute sequences of ordinary commands stored on files. UNIX, however, provides a full-fledged programming language for this purpose (the “shell”), with if, while, and case statements similar to those of Pascal, as well as extensive

facilities for string handling.

3.Input-output redirection. Any program invoked by a command can be told to take its input from, and/or write its output onto, a file rather than the user’s terminal. For example,

sort <alpha >beta

tells the sort program to take its input from alpha and write its output onto beta. UNIX also supports pipes, which allow one program to transmit its output directly into the input of another program.

See PIPE.

Many UNIX commands, called filters, read a file and output a copy of it that has undergone some simple transformation, such as removing repeated lines. Powerful operations can be accomplished by stringing filters together through pipes.

unsharp masking

504

4.Tree-structured directories. In all earlier operating systems, a user’s files were kept in a single list called a DIRECTORY. In UNIX, however, directories are handled like files, and a user can have an unlimited number of them, each of which must be listed in a higher directory until the main (“root”) directory is reached. This makes it possible to arrange files into logical groups—for example, to put all files related to a particular project into a single directory. Treestructured directories are a virtual necessity if one user is to keep track of more than a few dozen files.

The following are some common UNIX commands:

cc	Compile a C Program. (See C.)
cp	Copy a file onto a file or into a directory.
diff	Display the differences between two text files.
grep	Search a file for lines matching a pattern.
ls	List contents of a directory.
mkdir	Create a directory.
lpr	Print a file.
rm	Remove (delete) a file.
rmdir	Delete a directory (which must be empty).
cat	Copy file from standard input to standard output.
chmod	Change file permissions.

See also /DEV; /ETC; /HOME; /USR.

unsharp masking a method of sharpening an image by subtracting from it a blurred copy of itself. This was once done with photographic plates but is more easily done digitally, and most paint programs provide an unsharp masking filter. See also IMAGE PROCESSING and cross-references there.

FIGURE 283. Unsharp masking

uP (more properly µP, where µ is the Greek letter mu) abbreviation for

MICROPROCESSOR.

505

URL

uplevel pertaining to a later version of a product. For example, many Windows 3.1 programs are compatible with uplevel versions of Windows, such as Windows Vista. Contrast DOWNLEVEL.

uplink

1.a connection through which signals can be transmitted to a satellite.

Compare UPLOAD.

2.a connection from one hub to another hub. See HUB.

upload to transmit a file to a central computer from a smaller computer or a computer at a remote location. See FTP; KERMIT. Contrast DOWNLOAD.

UPnP (Universal Plug and Play) technology for standardizing connections between different devices. For information see the UPnP forum at www.upnp.org.

uppercase capital letters, such as A, B, C, as opposed to a, b, c (lowercase) or A, B, C (small caps). The term “ uppercase” goes back to the early days of letterpress printing. The metal type was kept in divided drawers called cases; the capital letters were traditionally kept in the upper case, and the small letters in the lower.

UPS

1.See UNINTERRUPTIBLE POWER SUPPLY.

2.(United Parcel Service) a major American carrier of packages for mail-order and e-tail businesses. (See E-TAIL.) Their web address is www.ups.com.

upstream (describing data transmission) in a direction from the client to the server, or from the peripheral to the main computer. Compare

UPLOAD. Contrast DOWNSTREAM.

upward compatibility the situation in which a computer program or accessory works not only on the machine for which it was designed but also on newer models. For instance, programs written for the IBM PC in 1981 will still run (considerably faster) on present-day Pentium machines. Thus we say that the Pentium is upward compatible with the processor in the PC. Contrast DOWNWARD COMPATIBILITY.

urban legend a story that is told by highly educated people as if it were true, but cannot be confirmed. Typically, it happened to a “friend of a friend” (i.e., a person who is almost, but not quite, identifiable), and it involves some improbable but highly amusing misadventure. The term was coined by Jan Harold Brunvand, who has written several books on the subject. The Internet is one of many means by which urban legends circulate. See also HOAX.

URL (Uniform Resource Locator, Universal Resource Locator) a way of specifying the location of publicly available information on the Internet, in the form

protocol://machine:port number/filename