Tuxedo
Tuxedo (which stands for Transactions for UNIX, Enhanced for Distributed Operation) is a middleware product that uses a message-based communications system to distribute applications across various operating system platforms and databases. Tuxedo operates as an extension of the operating system: as a platform for execution as well as development, it is designed for the creation and administration of e-commerce online transaction processing (OLTP) systems. Originally developed at AT&T in the 1970s, Tuxedo was subsequently owned by Unix System Laboratories (USL), and then Novell before it was taken over by BEA Systems, the current owners.
Tuxedo’s three main functions are: as middleware, to relay request and response communications between servers and clients; as a transaction processing (TP) monitor, to initiate, monitor, and terminate transactions; and, as a distributed TP monitor, to enable interaction between transaction participants on different machines and associated with different databases. The Gap, E*TRADE, and Hong Kong International Terminals are some organizations that use Tuxedo for large scale transaction processing.
TWAIN
TWAIN is a widely-used program that lets you scan an image (using a scanner) directly into the application (such as PhotoShop) where you want to work with the image. Without TWAIN, you would have to close an application that was open, open a special application to receive the image, and then move the image to the application where you wanted to work with it. The TWAIN driver runs between an application and the scanner hardware. TWAIN usually comes as part of the software package you get when you buy a scanner. It’s also integrated into PhotoShop and similar image manipulation programs.
The software was developed by a work group from major scanner manufacturers and scanning software developers and is now an industry standard. In several accounts, TWAIN was an acronym developed playfully from ”technology without an important name.” However, the TWAIN Working Group says that after the name chosen originally turned out to be already trademarked, an 11th hour meeting of the group came up with TWAIN, deriving it from the saying ”Ne’er the twain shall meet,” because the program sits between the driver and the application. The name is not intended to be an acronym.
tweak freak
A tweak freak is a person who tinkers with hardware and/ or programming to a point approaching obsession. Sometimes the intent is to enhance system performance beyond the norm. But many tweak freaks engage in the activity largely because it is interesting, fun, and can be a learning experience. It can also be frustrating and at its worst, dangerous.
The term ”tweak” may have originated in the early days of electronics, when tweezers were used to adjust the position of a wire on a crystal of galena in order to detect amplitude-modulated (AM) radio broadcast signals. Nowadays, hardware and programs of all kinds can (and often should) be aligned or debugged for optimum performance; technicians and programmers call the process tweaking.
The tweaking of computers, especially software and operating systems, is not for the faint-of-heart. Excessive or improper tweaking can cause computers and Web browsers to become unstable. Vulnerability to virus or Trojan horse infection may be increased. Excessive downloading and installation of tweaks and patches can increase the probability of program conflicts and crashes. Some tweaks facilitate illegal or questionable use of the Internet, and should be avoided by people who respect the law and the rights of others (and who wish to stay out of court). Let the tweaker beware.
TweakUl
TweakUI is a software utility that lets Windows 9x, Windows NT, and Windows 2000 users modify the desktop user interface and other system characteristics to their liking. Using TweakUI, you can change the menu speed, how windows are animated, and a number of features about Microsoft Internet Explorer. TweakUI allows the user to change settings that are not easy to locate, including some in the system registry. For example, a user can speed up system startup by reducing the frequency with which the ScanDisk utility is run.
Microsoft includes TweakUI as one of several ”Power Toys” that can be optionally installed. Users are advised to always back up their registry (for example, copy it to a new file with another name) before doing anything that might modify it.
twinaxial cable
Twinaxial cable is coaxial cable that contains two inner conducting wires rather than one. IBM’s AS/400 and System/3x midrange computer systems use twinaxial cable.
twip
A twip (twentieth of a point) is a measure used in laying out space or defining objects on a page or other area that is to be printed or displayed on a computer screen. A twip is 1/ 1440th of an inch or 1/567th of a centimeter. That is, there are 1440 twips to an inch or 567 twips to a centimeter. The twip is 1/20th of a point, a traditional measure in printing. A point is approximately 1/72nd of an inch.
A number of computer software programs, notably Microsoft’s Visual Basic, as well as its rich text file format (RTF), require programmers to specify screen positions and image and icon sizes in twips rather than in another common measure, the pixel. Like the pixel, the twip can be adjusted in size as screen resolution is changed, but, unlike the pixel, expresses an absolute value for printing.
Since not all software development tools work with twips, a programmer may sometimes need to convert between twips and pixels, and the reverse.
twisted pair
(Also see categories of twisted pair cabling systems and registered jack.)
Twisted pair is the ordinary copper wire that connects home and many business computers to the telephone company. To reduce crosstalk or electromagnetic induction between pairs of wires, two insulated copper wires are twisted around each other. Each connection on twisted pair requires both wires. Since some telephone sets or desktop locations require multiple connections, twisted pair is sometimes installed in two or more pairs, all within a single cable. For some business locations, twisted pair is enclosed in a shield that functions as a ground. This is known as shielded twisted pair (STP). Ordinary wire to the home is unshielded twisted pair (UTP).
Twisted pair is now frequently installed with two pairs to the home, with the extra pair making it possible for you to add another line (perhaps for modem use) when you need it. Twisted pair comes with each pair uniquely color coded when it is packaged in multiple pairs. Different uses such as analog, digital, and Ethernet require different pair multiples.
Although twisted pair is often associated with home use, a higher grade of twisted pair is often used for horizontal wiring in LAN installations because it is less expensive than coaxial cable.
The wire you buy at a local hardware store for extensions from your phone or computer modem to a wall jack is not twisted pair. It is a side-by-side wire known as silver satin. The wall jack can have as many five kinds of hole arrangements or pinout, depending on the kinds of wire the installation expects will be plugged in (for example, digital, analog, or LAN) . (That’s why you may sometimes find when you carry your notebook computer to another location that the wall jack connections won’t match your plug.)
two-way pager
A two-way pager is a pager that allows you to send data as well as receive it. In some cases, a two-way pager can serve as an alternative to a cellular telephone. At least one manufacturer, Paging Network, lets you record a message and have an answering service on the machine.
Apple Computer, Hewlett-Packard, MobileMedia Corporation, Motorola, AirTouch Communications, Casio Computer, Mobile Telecommunication Technologies (Mtel), and Sharp are among companies that manufacture two-pagers or offer a two-way paging service.
typeface
A typeface is a design for a set of printer or display fonts, each for a set of characters, in a number of specific sizes. Since outline fonts such as TrueType and Type 1 are scalable, a computer typeface designer must anticipate the possibility of the design being scaled through a range of sizes.
Typefaces often come as a family of typefaces, with individual typefaces for italic, bold, and other variations in the main design.
typosquatting
Typosquatting is a form of Internet cybersquatting, based on the probability that a certain number of Internet users will mistype the name of a Web site (or actually its URL) when surfing the Web. Typically, a typosquatter will register several possible input errors for a ”brand name” Web site
known for its high traffic, and then monitor to see how many clicks a day each of their "typo" domain names receives, and use the information to sell advertising for the sites that receive a high volume of accidental traffic. Advertising revenue might come from selling ads to the original site’s competitors or by providing redirect pages to related products or services.
u
A U is a standard unit of measure for designating the height in computer enclosures and rack cabinets. A U equals 1.75 inches. For example, a 4U chassis is 7 inches high. A 40U rack cabinet is 70 inches high.
U interface
In Integrated Services Digital Network (ISDN) Basic Rate Interface service, a U interface is the electrical interface for the single twisted pair wire connection from a local phone company (the central office) to a home or business. Unlike a regular 64 Kbps analog phone connection, however, the twisted-pair using ISDN carries two 64 Kbps channels (known as B, or bearer, channels) and an additional 16 Kbps channel (the D, for data or delta, channel) for control signals.
The U interface twisted-pair is usually connected at the home or business to a network terminator 1 (NT1) box, sometimes called a network terminating unit. (In the UK and some other countries, the NT1 is located at the central office.) The other side of the NT1 has plugs for four wires, which can be connected on a loop configuration known as an S-bus or S interface to up to eight devices (for example, two computers and six phones) or to a T interface. An NT1 can also be integrated into a modem or other device, in which case the ISDN connection can only serve that device.
The U-loop or U-V loop, as it is sometimes called, uses the 2B1Q line code protocol, meaning that two binary digits are used to represent one quadratude—that is, four possible variations of signal level (amplitude and polarity). Communication is full-duplex, meaning that data can be arriving at the same time you are sending data.
The U-V loop replaces the traditional local loop. The maximum distance for the ISDN loop is 6,500 meters (about 18,000 feet).
The following table summarizes the various ISDN electrical interfaces at different demarcation points or places in the traffic flow:
|
Electrical interface |
Between what two points |
|
U interface |
Central office and NT1 |
|
T interface |
NT1 and NT2 devices (such |
|
as a PBX) |
|
|
S interface |
NT1 or NT2 and ISDN |
|
devices (such as a telephone |
|
|
or terminal adapter) |
|
|
R interface |
Terminal adapter and non- |
|
ISDN devices (such as a |
|
|
computer) |
|
Electrical interface |
Between what two points |
|
V interface |
Within the ISDN node at the central office; separates line termination equipment from exchange termination equipment |
UART
A UART (Universal Asynchronous Receiver/Transmitter) is the microchip with programming that controls a computer’s interface to its attached serial devices. Specifically, it provides the computer with the RS-232C Data Terminal Equipment (DTE) interface so that it can "talk" to and exchange data with modems and other serial devices. As part of this interface, the UART also:
• Converts the bytes it receives from the computer along parallel circuits into a single serial bit stream for outbound transmission
• On inbound transmission, converts the serial bit stream into the bytes that the computer handles
• Adds a parity bit (if it’s been selected) on outbound transmissions and checks the parity of incoming bytes (if selected) and discards the parity bit
• Adds start and stop delineators on outbound and strips them from inbound transmissions
• Handles interrupts from the keyboard and mouse (which are serial devices with special ports)
• May handle other kinds of interrupt and device management that require coordinating the computer’s speed of operation with device speeds
More advanced UARTs provide some amount of buffering of data so that the computer and serial devices data streams remain coordinated. The most recent UART, the 16550, has a 16-byte buffer that can get filled before the computer’s processor needs to handle the data. The original UART was the 8250. If you purchase an internal modem today, it probably includes a 16550 UART (although you should ask when you buy it). According to modem manufacturer US Robotics, external modems do not include a UART. If you have an older computer, you may want to add an internal 16550 to get the most out of your external modem.
UDDI
UDDI (Universal Description, Discovery, and Integration) is an XML-based registry for businesses worldwide to list themselves on the Internet. Its ultimate goal is to streamline online transactions by enabling companies to find one another on the Web and make their systems interoperable for e-commerce. UDDI is often compared to a telephone book’s white, yellow, and green pages. The project allows businesses to list themselves by name, product, location, or the Web services they offer.
Microsoft, IBM, and Ariba spearheaded UDDI. The project now includes 130 companies, including some of the biggest names in the corporate world. Compaq, American Express, SAP AG, and Ford Motor Company are all committed to UDDI, as is Hewlett-Packard, whose own XML-based directory approach, called e-speak, is now being integrated with UDDI.
While the group does not refer to itself as a standards body, it does offer a framework for Web services integration. The UDDI specification utilizes World Wide Web Consortium (W3C) and Internet Engineering Task Force (IETF) standards such as XML, HTTP, and Domain Name System (DNS) protocols. It has also adopted early versions of the proposed Simple Object Access Protocol (SOAP) messaging guidelines for cross platform programming.
In November 2000, UDDI entered its public beta-testing phase. Each of its three founders—Microsoft, IBM, and Ariba—now operates a registry server that is interoperable with servers from other members. As information goes into a registry server, it is shared by servers in the other businesses. In the future, other companies will act as operators of the UDDI Business Registry. UDDI registration is open to companies worldwide, regardless of their size.
UDP
UDP (User Datagram Protocol) is a communications protocol that offers a limited amount of service when messages are exchanged between computers in a network that uses the Internet Protocol (IP). UDP is an alternative to the Transmission Control Protocol (TCP) and, together with IP, is sometimes referred to as UDP/IP. Like the Transmission Control Protocol, UDP uses the Internet Protocol to actually get a data unit (called a datagram) from one computer to another. Unlike TCP, however, UDP does not provide the service of dividing a message into packets (datagrams) and reassembling it at the other end. Specifically, UDP doesn’t provide sequencing of the packets that the data arrives in. This means that the application program that uses UDP must be able to make sure that the entire message has arrived and is in the right order. Network applications that want to save processing time because they have very small data units to exchange (and therefore very little message reassembling to do) may prefer UDP to TCP. The Trivial File Transfer Protocol (TFTP) uses UDP instead of TCP.
UDP provides two services not provided by the IP layer. It provides port numbers to help distinguish different user requests and, optionally, a checksum capability to verify that the data arrived intact.
In the Open Systems Interconnection (OSI) communication model, UDP, like TCP, is in layer 4, the Transport layer.
UHF
The UHF (ultrahigh frequency) range of the radio spectrum is the band extending from 300 MHz to 3 GHz. The wavelengths corresponding to these limit frequencies are 1 meter and 10 centimeters.
In the UHF band, signals from earth-based transmitters are not returned by the ionosphere to the surface; they always pass into space. Conversely, signals from space always penetrate the ionosphere and reach the surface. The global ”shortwave” propagation familiar to users of lower frequencies is unknown at UHF. The troposphere can cause bending, ducting, and scattering at UHF, extending the range of communication significantly beyond the visual horizon. Auroral, meteor-scatter, and EME (earth-moon-earth, also called moonbounce) propagation are sometimes observed, but these modes do not offer reliable communication and are of interest primarily to amateur radio operators. In the upper portion of the band, waves can be focused or collimated by dish antennas of modest size.
The UHF band is extensively used for satellite communication and broadcasting, in cellular telephone and paging systems, and by third-generation (3G) wireless services. Because the frequency is high and the band is vast (a span of 2.7 gigahertz from the low end to the high end), wideband modulation and spread spectrum modes are practical. Channels and subbands within the UHF portion of the radio spectrum are allocated by the International Telecommunication Union (ITU).
UIML
UIML (User Interface Markup Language) is a descriptive language that lets you create a Web page that can be sent to any kind of interface device—for example, to a PC with a large display and a keyboard or to a ”smart phone” with a tiny display and no keyboard. The advantage of UIML is that Web content can be created once without understanding the existing and future device types to which the content will be sent. A content developer uses the markup language (sometimes referred to as a set of tags) to describe user interface elements such as input boxes, text messages, menus, and buttons. A programmer can then write applications that use the UIML page to generate a page appropriate to each device type, such as a PC, smart phone, or voice output device, to which the content may need to be sent.
UIML is an application of the Extensible Markup Language (XML). One can think of it as the XML description that describes the data structure (names of fields or elements) of a user interface. A given UIML file also describes the specific content (text, names of images, and so forth) in those fields or elements. UIML also allows you to describe possible user input events and resulting actions. The markup is described in the UIML Specification, which also includes the formal XML document type definition (DTD) for UIML. Since UIML requires the specification of user interface elements (often called widgets) in terms of names used by specific language development toolkits (for example, Java AWT or Microsoft Foundation Classes—MFCL), you need to identify the specific tookit and know the names for various elements and their properties that are used by the toolkit.
Harmonia, the software company where UIML was developed, has published it as an open source language and plans to submit it to a standards organization after comments have been received on version 2.0.
Ultra DMA
Ultra DMA (UDMA, or, more accurately, Ultra DMA/33) is a protocol for transferring data between a hard disk drive through the computer’s data paths (or bus) to the computer’s random access memory (RAM). The Ultra DMA/33 protocol transfers data in burst mode at a rate of 33.3 MBps (megabytes per second), twice as fast as the previous Direct Memory Access (DMA) interface.
Ultra DMA was developed as a proposed industry standard by the Quantum Corporation, makers of hard disk drives, and Intel, makers of chipsets that support computer bus technology.
Ultra DMA support in your computer means that it will boot (start) and open new applications more quickly. It will also help users of graphics-intensive and other applications that require large amounts of access to data on the hard drive. Ultra DMA uses Cyclical Redundancy Checking (CRC), offering a new level of data protection.
Because the Ultra DMA protocol is designed to work with legacy application PIO and DMA protocols, it can be added to many existing computers by installing an Ultra DMA/33 Peripheral Component Interconnect adapter card. Ultra DMA uses the same 40-pin Integrated Drive Electronics interface cable as PIO and DMA.
