Abwatt
The abwatt (symbolized abW) is the unit of power in the cgs (centimeter/gram/second) electromagnetic system of units. In a direct-current (DC) circuit, 1 abW is the power dissipated, radiated, or expended when one abvolt (1 abV) of potential difference drives a current of one abampere (1 abA) through a component.
In a DC circuit, or in an alternating-current (AC) circuit in which there is no reactance, the following formula holds:
P = EI
where P is the power in abwatts, E is the potential difference in abvolts, and I is the current in abamperes.
The abwatt is a small unit of power, equivalent to 10-7 watt (W) or 0.1 microwatt (|W). The abwatt, by coincidence, is the same size as the statwatt (statW), the unit of power in the cgs electrostatic system of units. But in most applications, the watt, which is the unit of power in the International System of Units (SI), is preferred.
Also see power, watt, cgs or small-unit metric system, and International System of Units (SI).
Accelerated Graphics Port
AGP (Accelerated Graphics Port) is an interface specification that enables 3-D graphics to display quickly on ordinary personal computers. AGP is an interface designed to convey 3-D images (for example, from Web sites or CD-ROMs) much more quickly and smoothly than is possible today on any computer other than an expensive graphics workstation. The interface uses your computer’s main storage (RAM) for refreshing the monitor image and to support the texture mapping, z-buffering, and alpha blending required for 3-D image display. The AGP main memory use is dynamic, meaning that when not being used for accelerated graphics, main memory is restored for use by the operating system or other applications. Intel, which has taken the lead in developing its specifications, introduced AGP into a chipset for its Pentium microprocessor. The newer, faster microchips in Intel’s Pentium line are designed to work with the AGP chipset. Intel says the advanced floating point unit and faster cache algorithm of the more advanced Pentiums are better adapted for 3-dimensional applications.
Accelerated Hub Architecture
Accelerated Hub Architecture (AHA) (also called Intel Hub Architecture) is an Intel 800-series chipset design that uses a dedicated bus to transfer data between the two main processor chips instead of using the Peripheral Component Interconnect (PCI) bus, which was used in previous chipset architectures. The Accelerated Hub Architecture provides twice the bandwidth of the traditional PCI bus architecture at 266 MB per second. The Accelerated Hub Architecture consists of a memory controller hub and an input/output (I/O) controller hub (a controller directs or manages access to devices). The memory controller hub provides the central processing unit (CPU) interface, the memory interface, and the accelerated graphics port (AGP) interface. The memory controller hub supports single or dual processors with up to 1 GB of memory. The memory controller hub also allows for simultaneous processing, which enables more life-like audio and video capabilities.
The I/O controller hub provides a direct connection from the memory to the I/O devices, which includes any built-in modem and audio controllers, hard drives, Universal Serial Bus (USB) ports, and PCI add-in cards. The I/O controller hub also includes the Alert on LAN (local area network) feature that sounds an alert when software failures or system intrusion occurs.
Acceptable use policy
An acceptable use policy (AUP) is a policy that a network access user must agree to follow in order to be provided with access service. When you sign up with an Internet service provider (ISP), you will usually be presented with an AUP, which states that you agree to adhere to stipulations such as:
• Not using the service as part of violating any law
• Not attempting to break the security of any computer network or user
• Not posting commercial messages to Usenet groups without prior permission
• Not attempting to send junk e-mail or spam to anyone who doesn’t want to receive it
• Not attempting to mail bomb a site with mass amounts of e-mail in order to flood their server.
Users also typically agree to report any attempt to break into their accounts. A number of spammers have had their access service terminated.
Access
Access is simply being able to get to what you need. Data access is being able to get to (usually having permission to use) particular data on a computer. Web access means having a connection to the World Wide Web through an access provider or an online service provider such as America Online.
For data access, access is usually specified as read-only access and read/write access.
Access control list
An access control list (ACL) is a table that tells a computer operating system which access rights each user has to a particular system object, such as a file directory or individual file. Each object has a security attribute that identifies its access control list. The list has an entry for each system user with access privileges. The most common privileges include the ability to read a file (or all the files in a directory), to write to the file or files, and to execute the file (if it is an executable file, or program). Microsoft Windows NT/2000, Novell’s NetWare, Digital’s OpenVMS, and UNIX-based systems are among the operating systems that use access control lists. The list is implemented differently by each operating system.
In Windows NT/2000, an access control list (ACL) is associated with each system object. Each ACL has one or more access control entries (ACEs) consisting of the name of a user or group of users. The user can also be a role name,such as "programmer," or "tester." For each of these users, groups, or roles, the access privileges are stated in a string of bits called an access mask. Generally, the system administrator or the object owner creates the access control list for an object.
Access log
An access log is a list of all the requests for individual files that people have requested from a Web site. These files will include the HTML files and their imbedded graphic images and any other associated files that get transmitted. The access log (sometimes referred to as the "raw data") can be analyzed and summarized by another program.
In general, an access log can be analyzed to tell you:
• The number of visitors (unique first-time requests) to a home page
• The origin of the visitors in terms of their associated server’s domain name (for example, visitors from .edu, .com, and .gov sites and from the online services)
• How many requests for each page at the site, which can be presented with the pages with most requests listed first
• Usage patterns in terms of time of day, day of week, and seasonally
Access log keepers and analyzers can be found as shareware on the Web or may come with a Web server.
access method
1) In computing, an access method is a program or a hardware mechanism that moves data between the computer and an outlying device such as a hard disk (or other form of storage) or a display terminal. The term is sometimes used to refer to the mechanics of placing or locating specific data at a particular place on a storage medium and then writing the data or reading it. It is also used to describe the way that data is located within a larger unit of data such as a data set or file.
2) An access method is also an application program interface (API) that a programmer uses to create or access data sets or to read from or write to a display terminal or other output device. Examples are the Virtual Sequential Access Method (VSAM) and the Virtual Telecommunication Access Method (VTAM).
access provider
An access provider is any organization that arranges for an individual or an organization to have access to the Internet. Access providers are generally divided into two classes: Internet access providers (ISPs) and online service providers (OSPs). ISPs can be local businesses that pay for a highspeed connection to one of the companies (such as AT&T, Sprint, or MCI in the U.S.) that are part of the Internet. They can also be national or international companies that have
their own networks (such as AT&T’s WorldNet or IBM’s Global Services). OSPs, sometimes just called "online services,” also have their own networks but provide additional information services not available to non-subscribers. America Online is the most successful example of an OSP.
A typical charge from an access provider for an individual account is $10—30 U.S. a month, depending on the amount of usage you contract for. Hours of use beyond the arranged number are billed as an extra charge at an hourly rate. Both national and local access providers compete for business in national and local publications.
Microsoft’s Windows systems offer personal computer users access to the Microsoft Internet service as well as to America Online, IBM, and several other services.
An access provider may have its own point-of-presence (POP) on the Internet, or it may be a company that has a telecommunication connection to someone else with a POP.
An access provider is not the same as a "space provider" (virtual host), a company that provides space and management for individual or business Web sites. However, some access providers do provide a certain amount of space for a Web site as part of their service.
access time
Access time is the time from the start of one storage device access to the time when the next access can be started. Access time consists of latency (the overhead of getting to the right place on the device and preparing to access it) and transfer time.
The term is applied to both random access memory (RAM) access and to hard disk and CD-ROM access. For RAM access, IBM prefers the term cycle time. However, the use of access time for RAM access is common. Access time to RAM is usually measured in nanoseconds. Access time to a hard disk or CD-ROM is usually measured in milliseconds.
ACID
ACID (atomicity, consistency, isolation, and durability) is an acronym and mnemonic device for learning and remembering the four primary attributes ensured to any transaction by a transaction manager (which is also called a transaction monitor). These attributes are: Atomicity. In a transaction involving two or more discrete pieces of information, either all of the pieces are committed or none are.
Consistency. A transaction either creates a new and valid state of data, or, if any failure occurs, returns all data to its state before the transaction was started. Isolation. A transaction in process and not yet committed must remain isolated from any other transaction. Durability. Committed data is saved by the system such that, even in the event of a failure and system restart, the data is available in its correct state.
The ACID concept is described in ISO/IEC 10026-1:1992 Section 4. Each of these attributes can be measured against a benchmark. In general, however, a transaction manager or monitor is designed to realize the ACID concept. In a distributed system, one way to achieve ACID is to use a (2PC), which ensures that all involved sites must commit to transaction completion or none do, and the transaction is rollback.
acoustic coupler
An acoustic coupler is a hardware device that enables a modem (a device that converts signals from analog to digital and from digital back to analog) to connect to a voice circuit. A handset adapter is used to receive modem tones through the handset’s mouthpiece, and the earpiece is used to transmit these tones to the modem.
Acrobat
Acrobat is a program from Adobe that lets you capture a document and then view it in its original format and appearance. Acrobat is ideal for making documents or brochures that were designed for the print medium viewable electronically and capable of being shared with others on the Internet. To view an Acrobat document, which is called a Portable Document Format (PDF) file, you need Acrobat Reader. The Reader is free and can be downloaded from Adobe. You can use it as a standalone reader or as a plug-in in a Web browser.
Acrobat is actually a set of products. The latest version includes a ”toolkit” that lets you scan in or otherwise capture documents created with Word, Pagemaker, and other desktop publishing products. The resulting PDF files can then be available for viewing either directly with the Reader or they can be viewed as embedded files within the browser.
acronym
An acronym (pronounced AK-ruh-nihm, from Greek acro- in the sense of extreme or tip and onyma or name) is an abbreviation of several words in such a way that the abbreviation itself forms a word. According to Webster’s, the word doesn’t have to already exist; it can be a new word. Webster’s cites ”snafu” and ”radar”, two terms of World War Two vintage, as examples. Implicit is the idea that the new word has to be pronounceable and ideally easy to remember.
Frequently, acronyms are formed that use existing words (and sometimes the acronym is invented first and the phrase name represented is designed to fit the acronym). Here are some examples of acronyms that use existing words:
BASIC….Beginner’s All-Purpose Symbolic Instruction Code
NOW…..National Organization for Women
WHO…..World Health Organization
Abbreviations that use the first letter of each word in a phrase are sometimes referred to as initialisms. Initialisms can be but are not always acronyms. AT&T, BT, CBS, CNN, IBM, and NBC are initialisms that are not acronyms. Many acronym lists you’ll see are really lists of acronyms and initialisms or just lists of abbreviations. (Note that abbreviations include shortened words like ”esp” for ”especially” as well as shortened phrases.) Summing up:
• An abbreviation is a shortening of a word or a phrase.
• An acronym is an abbreviation that forms a word.
• An initialism is an abbreviation that uses the first letter of each word in the phrase (thus, some but not all initialisms are acronyms).
By the way, an acronym so familiar that no one remembers what it stands for is called an anacronym.
ACTA
ACTA (America’s Carriers Telecommunications Association) is a lobbying organization for over 165 small longdistance telephone carrier companies. It was organized in 1985 to represent the interests of the group before legislative and regulatory bodies. The organization is based in Casselberry, Florida.
Active Directory
Active Directory is Microsoft’s trademarked directory service, an integral part of the Windows 2000 architecture. Like other directory services, such as Novell Directory Services (NDS), Active Directory is a centralized and standardized system that automates network management of user data, security, and distributed resources, and enables interoperation with other directories. Active Directory is designed especially for distributed networking environments.
Active Directory features include:
• Support for the X.500 standard for global directories
• The capability for secure extension of network operations to the Web
• A hierarchical organization that provides a single point of access for system administration (management of user accounts, clients, servers, and applications, for example) to reduce redundancy and errors
• An object-oriented storage organization, which allows easier access to information
• Support for the Lightweight Directory Access Protocol (LDAP) to enable inter-directory operability
• Designed to be both backward compatible and forward compatible
active matrix display
Active matrix (also known as thin film transistor) is a technology used in the flat panel liquid crystal displays of notebook and laptop computers. Active matrix displays provide a more responsive image at a wider range of viewing angle than dual scan (passive matrix) displays.
Desktop computer displays or monitors usually have cathode ray tube technology.
active network
An active network is a network in which the nodes are programmed to perform custom operations on the messages that pass through the node. For example, a node could be programmed or customized to handle packets on an individual user basis or to handle multicast packets differently than other packets. Active network approaches are expected to be especially important in networks of mobile users. "Smart packets" use a special self-describing language that allows new kinds of information to be carried within a packet and operated on by a node.
A Secure Active Network Environment (SANE) is an architecture for a trusted or secure active network.
Active Server Page_
ASP is also an abbreviation for application service provider.
An Active Server Page (ASP) is an HTML page that includes one or more scripts (small embedded programs) that are processed on a Microsoft Web server before the page is sent to the user. An ASP is somewhat similar to a server-side include or a common gateway interface (CGI) application in that all involve programs that run on the server, usually tailoring a page for the user. Typically, the script in the Web page at the server uses input received as the result of the user’s request for the page to access data from a database and then builds or customizes the page on the fly before sending it to the requestor.
ASP is a feature of the Microsoft Internet Information Server (IIS), but, since the server-side script is just building a regular HTML page, it can be delivered to almost any browser. You can create an ASP file by including a script written in VBScript or JScript in an HTML file or by using ActiveX Data Objects (ADOs) program statements in the HTML file. You name the HTML file with the ".asp" file suffix. Microsoft recommends the use of the server-side ASP rather than a client-side script, where there is actually a choice, because the server-side script will result in an easily displayable HTML page. Client-side scripts (for example, with JavaScript) may not work as intended on older browsers.
Active Template Library
Active Template Library (ATL), formerly called ActiveX Template Library) is a Microsoft program library (set of prepackaged program routines) for use when creating Active Server Page (ASP) code and other ActiveX program components with C++ (including Visual C++). A Web site developer that wants to forward user requests to a program in the Web server can write a common gateway interface application or, if the server is Microsoft’s Internet Information Server (IIS), can include a script in the HTML (Web) page. The page itself is called an Active Server Page (ASP) and has a suffix of .asp. The script in the Active Server Page is interpreted and performed at the server before the page is sent on to the user. Another approach is to have this script (written in Microsoft’s VBScript or JScript) in turn call a compiled program, written typically in C++, a sophisticated object-oriented programming language. Since a compiled program runs faster than a script, the Web page will be formulated faster and returned more quickly to the user. A C++ program also can interface more closely with the operating system than a script can, and there are several other advantages. On the other hand, it is more difficult and time-consuming to write a program in C++ than to write one in a script language.
The Active Template Library lets the programmer build Component Object Models object that can be called by the script on an ASP page. These objects are described by Microsoft as being fast and having industrial strength. Objects you can build using the ATL include full controls, Internet Explorer controls, property pages, and dialog boxes.
