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Glossary


access control entry See ACE.

access control list See ACL.

ACE (access control entry) Part of the Windows NT security API used by the system to define a user's or group's rights. It defines the object rights for a single user or group. Every ACE has a header that defines the type, size, and flags for the ACE. Next comes an access mask that defines the rights a user or group has to the object. Finally, there's an entry for the user's or group's security identifier (SID).

ACL (access control list) Part of the Windows NT security API used to determine both access and monitoring properties for an object. Each ACL contains one or more ACEs (access control entries) that define the security properties for an individual or group. There are two major ACL groups: SACL (security access control list) and DACL (discretionary access control list). The SACL controls Windows auditing feature. The DACL controls actual access to the object.

American Standard Code for Information Interchange See ASCII.

API (Application Programming Interface) A method of defining a standard set of function calls and other interface elements. It usually defines the interface between a high-level language and the lower level elements used by a device driver or operating system. The ultimate goal is to provide some type of service to an application that requires access to the operating system or device feature set.

application independence A method of writing applications so that they don't depend on the specific features of an operating system or hardware interface. It normally requires the use of a high-level language and an API. The programmer also needs to write the application in such a way as to avoid specific hardware or operating system references. All user and device interface elements must use the generic functions provided by the API.

Application Programming Interface See API.

ASCII (American Standard Code for Information Interchange) A standard method of equating the numeric representations available in a computer to human-readable form. The number 32 represents a space, for example. The standard ASCII code contains 128 characters (7 bits). The extended ASCII code uses 8 bits for 256 characters. Display adapters from the same machine type usually use the same upper 128 characters. Printers, however, might reserve these upper 128 characters for nonstandard characters. Many Epson printers use them for the italic representations of the lower 128 characters, however.

bidirectional support Defines a printer's capability to transfer information both ways on a printer cable. Input usually contains data or printer control codes. Output usually contains printer status information or error codes.

binary value Refers to a base 2 data representation in the Windows registry. Normally used to hold status flags or other information that lends itself to a binary format.

BMP files Windows standard bitmap graphics data format. This is a raster graphic data format that doesn't include any form of compression. OS/2 can also use this data format to hold graphics of various types.

CAD (computer-aided drafting) A special type of graphics program used for creating, printing , storing, and editing architectural, electrical, mechanical, or other forms of engineering drawings. CAD programs normally provide precise measuring capabilities and libraries of predefined objects, such as sinks, desks, resistors, and gears.

CAS (Communicating Applications Specification) An older facsimile (fax) communications standard originally defined by Intel and Digital Communications Associates (DCA). Many DBMS libraries still use this standard because it provides a consistent method for defining fax communications even if the host machine contains multiple boards. In addition, the API provides a simple method for interacting with the host machine's hardware. Problems with this standard include the need to define a special initialization file for each fax board in the system and the high cost of the hardware itself.

CDFS (compact disc file system) The portion of the file subsystem specifically designed to interact with compact disc drives. It also provides the user interface elements required to tune this part of the subsystem. The CDFS takes the place of an FSD for CD-ROM drives.

CGA (color graphics adapter)

class ID See CLSID.

client The recipient of data, services, or resources from a file or other server. This term can refer to a workstation or an application. The server can be another PC or an application.

Client Services for NetWare See CSNW.

CLSID (Class ID) A method of assigning a unique identifier to each object in the registry. Also refers to various high-level language constructs.

CMOS (complementary metal oxide semiconductor) Normally refers to a construction method for low-power, battery-backed memory. When used in the context of a PC, this term usually refers to the memory used to store system configuration information and the real-time clock status. The configuration information normally includes the amount of system memory, the type and size of floppy drives, the hard drive parameters, and the video display type. Some vendors include other configuration information as part of this chip as well.

Communicating Applications Specification See CAS.

compact disc file system See CDFS.

complementary metal oxide semiconductor See CMOS.

Compressed Serial Line Internet Protocol See CSLIP.

Computer-aided design See CAD.

container Part of the object-oriented terminology that has become part of OLE. A container is a drive, file, or other resource used to hold objects. The container is normally referenced as an object itself.

CSLIP (Compressed Serial Line Internet Protocol) This is a type of connection supported by older UNIX remote servers. CSLIP works much like a SLIP connection, except it also adds file compression. Windows NT provides support for remote network connections as a client. It doesn't provide this support as a server.

CSNW (Client Services for NetWare) A special applet Windows NT adds to the Control Panel when you install NetWare support. The applet allows you to configure the NetWare connection.

DAT (digital audio tape) A tape drive that uses a cassette to store data. The cassette and the drive use the same technology as the audio version of the DAT drive. The internal circuitry of the drive formats the tape for use with a computer system, however. The vendor must also design the interface circuitry with computer needs in mind. DAT tapes allow you to store large amounts of information in a relatively small amount of space. Typical drive capacities range from 1.2GB to 8GB.

data communication exchange See DCE.

data link control See DLC.

datacentric The method used by modern operating systems to view the user interface from a data perspective rather than from the perspective of the applications used to create the data. Using this view allows users to worry more about manipulating the data on their machines than the applications required to perform a specific task.

DBMS (Database Management System) A method for storing and retrieving data based on tables, records, and fields. Each field represents a specific piece of data, such as an employee's last name. Records are made up of one or more fields. Each record is one complete entry in a table. A table contains one type of data, such as the names and addresses of all the employees in a company. It is composed of records (rows) and fields (columns), just like the tables you see in books. A database may contain one or more related tables. It may include a list of employees in one table, for example, and the pay records for each of those employees in a second table.

DCE (Data Communication Exchange) A specification created by the Open Software Foundation (OSF) that defines methods for data exchange between a client and server. The remote procedure call (RPC) support built into Windows NT is compatible with the DCE specification.

DDE (Dynamic Data Exchange) The capability to cut data from one application and paste it into another application. You can cut a graphics image created with a paint program, for example, and paste it into a word processing document. After it is pasted, the data doesn't reflect changes made to it by the originating application. DDE also provides a method for communicating with an application that supports it and requesting data. You can use an Excel macro to call Microsoft Word and request the contents of a document file, for example. Some applications also use DDE to implement file-association strategies. Microsoft Word, for example, uses DDE in place of command-line switches to gain added flexibility when a user needs to open or print a file.

device-independent bitmap See DIB.

DHCP (Dynamic Host Configuration Protocol) A method for automatically determining the IP address on a TCP/IP connection. A server provides this address to the client as part of the setup communications. Using DHCP means that a server can use fewer addresses to communicate with clients and that clients do not need to provide a hard-coded address to the server. You must configure your server to provide these services.

DIB (device-independent bitmap) A method of representing graphics information that doesn't reflect a particular device's requirements. This has the advantage of allowing the same graphic to appear on any device in precisely the same way, despite differences in resolution or other factors that normally change the graphic's appearance.

digital audio tape drive See DAT.

DIP switch A set of configuration switches normally found within a computer system. These switches control everything from the port addresses and IRQ settings on expansion boards, to the number of supported floppy drives on the motherboard. Most vendors use software settings stored in CMOS instead of DIP switches now to reduce the number of times a user needs to open the computer case.

direct cable connection A type of connection that relies on a serial or parallel cable instead of network cards or telephone communications. Direct cable connections have the advantage of being easy to implement and inexpensive. Negative features include low transmission rate and the inability to allow more than a single pair of PCs to talk with each other. Normally, direct cable connections are used for short-term data transfer between a desktop and laptop (or other portable) computer.

direct memory access See DMA.

disk defragmenter An application used to reorder the data on a long-term storage device, such as a hard or floppy disk drive. Reordering the data so that it appears in sequential order—file by file—reduces the time required to access and read it. The sequential order allows you to read an entire file without moving the disk head at all in some cases and only a little in others. This reduction in access time normally improves overall system throughput and therefore enhances system efficiency.

DLC (data link control) Normally, a protocol used to establish communications with a remote server. The Microsoft DLC provides connections to mainframes and network printers.

DLL (dynamic link library) A special form of application code loaded into memory by request. It is not executable by itself. A DLL does contain one or more discrete routines that an application may use to provide specific features. A DLL, for example, can provide a common set of file dialog boxes used to access information on the hard drive. More than one application may use the functions provided by a DLL, reducing overall memory requirements when more than one application is running.

DMA (direct memory access) A memory-addressing technique in which the processor doesn't perform the actual data transfer. This method of memory access is faster than any other technique.

DOS Protected-Mode Interface See DPMI.

DPMI (DOS Protected-Mode Interface) A method of accessing extended memory from a DOS application using the Windows extended memory manager.

drag and drop A technique used in object-oriented operating systems to access data without actually opening the file using conventional methods. This method allows the user to pick up a document file, drag it to the printer, and drop it, for example. The printer prints the document using its default settings.

dual-ported video RAM See VRAM.

Dvorak layout An alternative method of laying out the keyboard so that stress is reduced and typing speed is increased. It's different from the more familiar QWERTY layout used by most keyboards and typewriters.

dynamic data exchange See DDE.

Dynamic Host Configuration Protocol See DHCP.

dynamic link library See DLL.

EEMS (Enhanced Expanded Memory Specification) This specification defines one method of extending the amount of memory a processor can address from the conventional memory area. In 1986, AST Research Corporation, QUADRAM Corporation, and Ashton-Tate added some enhancements to the Lotus-Intel-Microsoft expanded memory specification (EMS). Their improved standard, EEMS, was a breakthrough in the PC industry. EEMS revised the hardware functions of memory cards to improve the software standard. With EEMS, areas larger than 64KB can be used as a page frame. The page frame can be mapped below 640KB, as well as between 640KB and 1MB. This permits entire programs to run in enhanced expanded memory.

EGA (Enhanced graphics adapter)

EMB (extended memory blocks) Refers to the remaining extended memory (above the high memory area) available to an extended memory specification (XMS) driver.

embedded systems A combination of processor, operating system, and device-specific applications used with a special-purpose device. The control used to set the time and temperature on a microwave is an embedded system, for example. Another form of embedded system is the computer that controls engine efficiency in a car.

EMF (enhanced metafile) Used as an alternative storage format by some graphics applications. This is a vector graphics format, so it provides a certain level of device independence and other features a vector graphic normally provides.

EMM (Expanded Memory Manager) A device driver like EMM386.EXE that provides expanded memory services on an 80386 and above machine. (Special drivers work with 80286 and a few 8088/8086 machines.) An application accesses expanded memory using a page frame or other memory-mapping techniques from within the conventional or upper memory area (0KB to 124KB). The EMM usually emulates expanded memory using extended memory managed by an extended memory manager (XMM) like HIMEM.SYS. An application must change the processor's mode to protected mode in order to use XMS. Some products, such as 386MAX.SYS and QEMM.SYS, provide both EMM and XMM services in one driver.

Emoticon A set of characters used to express body language or an emotion of some sort. Normally, the characters form some visual representation of the person's face. For example, :^) when viewed sideways looks like a person smiling. Emoticons normally appear within electronic mail where the sender's meaning may be unclear. Tongue-in-cheek comments or jokes present problems when sent in written format because the receiver might not always know how to interpret the message. An emoticon makes the meaning of the message clearer by presenting the intended body language or emotion with the written words.

EMS (Expanded Memory Specification) Several versions of this specification are in current use. The most popular version is 3.2, even though a newer 4.0 specification is available. This specification defines one method of extending the amount of memory a processor can address from the conventional memory area. It uses an area outside of system memory to store information. An EMM provides a window view into this larger data area. The old 3.2 specification requires a 64KB window in the UMB. The newer 4.0 specification can create this window anywhere in conventional or UMB memory.

Enhanced Expanded Memory Specification See EEMS.

enhanced memory blocks See EMB.

enhanced metafile See EMF.

enhanced mode A Windows operating mode that supports the capabilities of the 80386 and above processors. This means that Windows will use any extended memory found in the workstation by using the processor's protected mode. This mode also fully supports the virtual memory capabilities of the 80386, which means that the size of the hard disk's swap files plus the amount of physical RAM determines the amount of memory available for applications. You also receive the full multitasking capabilities of the 80386 using this mode.

expanded memory manager See EMM.

expanded memory specification See EMS.

eXtended Memory Specification See XMS.

FAT (file allocation table) The method of formatting a hard disk drive used by DOS and other operating systems. This technique is one of the oldest formatting methods available.

file allocation table disk format See FAT.

file system driver See FSD.

floptical drive A special form of storage media that combines the flexibility of floppy disks with the storage capacity of optical drives. A typical floptical drive can read both optical media and standard floppy disks. These drives can hold 20MB (or more) of data when using optical media. Another form reads only optical media. Storage capacities for these drives are higher—usually, 135MB (or more)—and access times are better because the drive doesn't have to turn at the slower floppy rate.

Forum An on-line service area set aside for people with common interests. A forum normally contains three areas: message (section), file storage (library), and live conversation (conference room). A common topic might include a specific product such as Word for Windows, or an idea such as Plug and Play, or even a hobby such as wine tasting. The interest areas are further divided into specific sections. A Word for Windows forum, for example, might contain a section devoted to those with installation questions.

frame buffer A piece of system memory set aside to represent video memory. An application draws on the system memory rather than actual video memory to prevent conflicts when multiple applications need to draw at the same time. When the drawing on the buffer is complete, the entire buffer is sent to video memory at one time. Anything sent to video memory usually ends up on the display. This process is known as virtualization.

FSD (file system driver) A file subsystem component responsible for defining the interface between Windows and long-term storage. The FSD also defines features such as long file names and what types of interaction the device supports. The CD-ROM FSD, for example, won't support file writes unless you provide a device that can perform that sort of task.

GDI (Graphics Device Interface) One of the main Windows root components. It controls the way that graphics elements are presented on-screen. Every application must use the API provided by this component to draw or perform other graphics-related tasks.

GDT (global descriptor table) A memory construct that contains the information required to control all the extended memory in an 80386 or above processor. The GDT normally passes control of smaller memory segments to the LDTs used by an individual application.

general protection fault See GPF.

global descriptor table See GDT.

GPF (general protection fault) A processor or memory error that occurs when an application makes a request the system can't honor. This type of error results in some type of severe action on the part of the operating system. Normally, the operating system terminates the offending application.

Graphical User Interface See GUI.

Graphics Device Interface See GDI.

GUI (Graphical User Interface) A system of icons and graphics images that replaces the character-mode menu system used by many machines. The GUI can ride on top of another operating system (such as DOS or UNIX) or reside as part of the operating system itself (such as Windows or OS/2). Advantages of a GUI are ease of use and high-resolution graphics. Disadvantages are higher workstation hardware requirements and lower performance over a similar system using a character-mode interface.

HAL (hardware abstraction layer) A conceptual element of the Windows NT architecture. Microsoft wrote the drivers and other software elements so that they could easily move Windows NT to other platforms. That's how they moved Windows NT to the MIPS and Alpha Machines. The basic architecture of Windows NT is the same, but the low level drivers the ones that directly interface with the hardware—are different. The important thing to remember is that as far as your application is concerned, it's still running on an Intel machine. The only time you'll run into trouble is if your application bypasses the Windows API and goes directly to the hardware.

hardware abstraction layer See HAL.

high memory area See HMA.

high performance file system See HPFS.

HMA (high memory area) The 64KB area of memory beyond the 1MB boundary that the processor can access in real mode on an 80286 or above processor.

HPFS (high performance file system) The method of formatting a hard disk drive used by OS/2. Although it provides significant speed advantages over other formatting techniques, only the OS/2 operating system and applications designed to work with that operating system can access a drive that was formatted using this technique.

HTML (hypertext markup language) One method of displaying text, graphics, and sound on the Internet. HTML provides an ASCII-formatted page of information read by a special application called a browser. Depending on the browser's capabilities, some key words are translated into graphics elements, sounds, or text with special characteristics, such as color, font, or other attributes. Most browsers discard any keywords they don't understand, allowing browsers of various capabilities to explore the same page without problem. Obviously, there is a loss of capability if a browser doesn't support a specific keyword.

hypertext markup language See HTML.

ICM (image color matcher) A special component of the graphics subsystem that allows Windows to match the colors produced by one device with those available on another device. The result is that the output of both devices doesn't show the normal variations in color that Windows applications currently produce.

icon A symbol used to graphically represent the purpose and/or function of an application or file. A text file might appear as a sheet of paper with the file name below the icon, for example. Applications designed for the environment or operating system usually appear with a special icon depicting the vendor's or product's logo. Icons normally are part of a GUI environment or operating system, such as Windows or OS/2.

IFS manager (installable file system manager) The API component of the file subsystem. It provides a consistent interface that applications can use to access a variety of devices—local and remote. This component also provides a standard interface that device drivers can use to provide services, such as file opening and drive status.

image color matcher See ICM.

INF file A special form of device or application configuration file. It contains all the parameters Windows requires to install or configure the device or application. An application INF file might contain the location of data files and the interdependencies of DLLs, for example. Both application and device INF files contain the registry and INI file entries required to make Windows recognize the application or device.

inherited rights mask See IRM.

installable file system helper A special real-mode component of the IFS manager used to allow access of Windows drive functions by DOS applications. It uses the same DOS interface as before, but all processing is performed by the protected-mode manager.

installable file system manager See IFS manager.

interrupt request See IRQ.

IRM (inherited rights mask) A NetWare term describing the set of rights a person inherits as part of his trustee, group, file, and directory rights.

IRQ (interrupt request) The set of special address lines that connect a peripheral to the processor. Think of an IRQ as an office telephone with multiple incoming lines. Every time a device calls, its entry lights up on the front of the telephone. The processor selects the desired line and picks up the receiver to find out what the device wants. Everything works fine as long as there is one line for each device that needs to call the processor. If more than one device were to try to call in on the same line, the processor wouldn't know who was at the other end. This is the source of IRQ conflicts that you hear about from various sources. Older PC-class machines provided eight interrupt lines. The newer AT-class machines provide 16 interrupt lines. Only 15 of those lines are usable, however, because one of them is used for internal purposes.

LAN (local area network) A combination of hardware and software used to connect a group of PCs to each other and/or a mini- or mainframe computer. Two main networking models are in use: peer-to-peer and client/server. The peer-to-peer model doesn't require a dedicated server. In addition, all the workstations in the group can share resources. The client/server model uses a central server for resource sharing, but some special methods are provided for using local resources in a limited fashion.

lazy writes A method for writing data to disk that enables the operating system to use idle CPU time to its best advantage. Data is written to disk from a memory buffer when the CPU isn't engaged doing other tasks. The advantage to this method is an overall improvement in system response time and efficiency. Disadvantages include potential data loss if the user shuts off the system without forcing a write first. Under Windows NT and Windows 95, the forced write occurs during the shutdown sequence.

LDT (local descriptor table) A memory construct that controls access to the memory used by a single application or a group of applications that share the same memory. The LDT is subservient to the GDT that manages system memory overall.

light remote procedure call See LRPC.

listbox A windowing construct that contains a list of items. Normally, the user selects one or more of these items in order to respond to an application or operating system query.

local area network See LAN.

local descriptor table See LDT.

locally unique identifier See LUID.

LRPC (light remote procedure call) Essentially, a method for calling a procedure not associated with the current application or local machine. OLE 2 allows you to create links to other documents, even if they aren't physically located on the local drive. It implements this using an LRPC mechanism. Unfortunately, this linking mechanism has limitations. You'll find that it works fine with some peer-to-peer networks, for example, but it works only marginally with other network types.

LUID (locally unique identifier) Essentially, a pointer to a Windows NT security object. The object could include files, directories, or services. LUIDs provide an operating system reference to the object and works much like your social security number.

Macros A form of programming that records keystrokes and other program-related tasks to a file on disk or within the current document. Most applications provide a macro recorder that records the keystrokes and mouse clicks you make. This means that you don't even have to write them in most cases. Macros are especially popular in spreadsheets. Most macros use some form of DDE to complete OLE-related tasks.

management information file See MIF.

MAPI (messaging API) The set of functions and other resources Windows provides to communications programs. It allows the application to access a variety of communications channels using a single set of calls and without regard to media. This is the component of Windows 95 that allows Exchange to process information from e-mail and on-line services using the same interface.

MCA (microchannel architecture) A specialized bus introduced by IBM. It's faster than the old ISA bus and gives the operating system information about the peripheral devices connected to the bus. It also provides the means for devices to become self-configuring.

messaging API See MAPI.

microchannel architecture See MCA.

Microm Networking Protocol See MNP.

MIDI (Musical Instrument Digital Interface) A method for allowing musical instruments to interact with a computer system. One part of the specification defines special hardware needed to allow electronic communications between the device and the computer. The other part of the specification includes a file-storage technique that defines the note, volume, and other information required to re-create a musical sequence. Two common MIDI file format extensions are MID and RMI.

MIF (management information file) A special file used with Desktop Management Interface (DMI) support that contains all the particulars about a piece of equipment. When the System Management Server looks at a workstation and finds this file, it adds its contents to a SQL database that you can open with any number of products. Besides the hardware information, System Management Server adds the software-auditing information it finds to the database. The combined software and hardware information will give you the data required to know whether a particular workstation can run a piece of software without an upgrade.

miniport driver A specialized Windows component that provides access to a resource—normally, a peripheral device of some type. It's also used to access pseudo-devices and network resources.

MNP (Microm Networking Protocol) A standard method of error-correcting for modems. The precise differences between levels aren't important from a user prospective. A higher level is generally better. Essentially, MNP provides a method of sending data in larger blocks, eliminating some of the control characters that usually impede data transmission.

Motion Picture Experts Group See MPEG.

MPEG (Motion Picture Experts Group) A standards group that provides file formats and other specifications in regard to full-motion video and other types of graphics displays.

MPR (multiple provider router) A method of using more than one protocol with Windows. It allows you to mix and match protected-mode drivers on the same network. You can mix NetBEUI and IPX/SPX, for example, on the same network. In addition, some protocols automatically load when you request a specific service. The Microsoft data link control (DLC) falls into this category. It provides connections to mainframes and network printers. All network protocols require a network provider. The whole function of the MPR is to accept network requests from the API and send them to the appropriate network provider (NP).

MSD (Microsoft Diagnostic)

MSN (Microsoft Network)

MSP (Microsoft Press)

multiple-boot configuration A method of creating a configurable environment that was first introduced with DOS 5.0. The user simply selects the operating environment from a list of environments presented prior to the boot sequence. This technique provides an additional layer of flexibility and allows the user to optimize the operating environment to perform specific tasks.

multiple provider router See MPR.

multitasking The capability of some processor and environment/system combinations to perform more than one task at a time. The applications appear to run simultaneously. You can download messages from an on-line service, print from a word processor, and recalculate a spreadsheet all at the same time, for example. Each application receives a slice of time before the processor moves to the next application. Because the time slices are fairly small, it appears to the user that these actions are occurring simultaneously.

Musical Instrument Digital Interface See MIDI.

national language support See NLS.

NDIS (Network Device Interface Specification) A driver that translates each Windows-specific request into a call the NIC driver can understand. Using NDIS means that Windows can provide standardized requests regardless of NIC type, greatly enhancing flexibility and extensibility.

nested objects Two or more objects that are coupled in some fashion. The objects normally appear within the confines of a container object. Object nesting allows multiple objects to define the properties of a higher-level object. It also allows the user to associate different types of objects with each other.

Network Device Interface Specification See NDIS.

network interface card See NIC.

network provider See NP.

NIC (network interface card) The device responsible for allowing a workstation to communicate with the file server and other workstations. It provides the physical means for creating the connection. The card plugs into an expansion slot in the computer. A cable that attaches to the back of the card completes the communications path.

NLS (national language support) A method of reconfiguring the keyboard and other system components to support more than one language through the use of code pages. Each code page defines a different language configuration. Unfortunately, this technique doesn't change the language used for display purposes. In other words, NLS won't cause your English-language version of Windows to suddenly display prompts and other text in German.

NP (network provider) Performs all the protocol-specific functions an application requires under Windows. It will make or break connections, return network status information, and provide a consistent interface for the multiple provider router (MPR) to use.

NTFS (Windows NT file system) The method of formatting a hard disk drive used by Windows NT. Although it provides significant speed advantages over other formatting techniques, only the Windows NT operating system and applications designed to work with that operating system can access a drive that is formatted using this technique.

object conversion A method of changing the format and properties of an object created by one application to the format and properties used by another. Conversion moves the data from one application to another—usually without a loss in formatting, but always without a loss of content.

object linking and embedding See OLE.

ODBC (open database connectivity) One of several methods of exchanging data between DBMS. ODBC normally relies on SQL to translate DBMS-specific commands from the client into a generic language. The ODBC agents on the server translate these SQL requests into server-specific commands.

OLE (object linking and embedding) The process of packaging a file name and any required parameters into an object and then pasting this object into the file created by another application. You can place a graphics object within a word processing document or spreadsheet, for example. When you look at the object, it appears as if you simply pasted the data from the originating application into the current application (similar to DDE). When linked, the data provided by the object automatically changes as you change the data in the original object. When embedded, the data doesn't change unless you specifically edit it, but the data still retains its original format and you still use the original application to edit the data. Often, you can start the originating application and automatically load the required data by double-clicking on the object. The newer OLE 2 specification allows in-place data editing, as well as editing in a separate application window.

open database connectivity See ODBC.

OSF (Open Software Foundation)

password caching A method of saving the passwords for resources a user might need to access. The user still needs to enter the main password required to access Windows, but Windows remembers the passwords required to access other resources, such as a network or an on-line service that directly supports Windows password-caching capability.

PCX file A raster graphics data format originally used by ZSoft Paintbrush. This format has gone through many nonstandard transitions and occasionally presents problems when accessed by applications other than the original. It provides for various levels of color and includes data compression.

PD (port driver) Performs the task of communicating with the device through an adapter. It's the last stage before a message leaves Windows and the first stage when a message arrives from the device. The PD is usually adapter-specific. You would have one VxD for each hard drive and one PD for each hard drive adapter, for example.

PIF (program information file) A special configuration file Windows and OS/2 uses to define the environment for a DOS application. The PIF usually includes various memory settings, along with the application's command path and working directory.

Plug and Play The combination of BIOS, operating system, and peripheral device components that provides a self-configuring environment. This self-configuring feature allows the operating system to avoid potential hardware conflicts by polling the peripheral devices, assessing their requirements, and determining and implementing optimal settings for each device.

Point-to-Point Protocol See PPP.

port driver See PD.

POSIX A government-specified form of UNIX that's supposed to be portable across a variety of platforms. It appeared in 1988 as IEEE Standard 1003.1-1988.

POST (power-on self test) The set of diagnostic and configuration routines the BIOS runs during system initialization. The memory counter you see during the boot sequence is part of this process, for example.

power-on self test See POST.

PPP (Point-to-Point Protocol) A set of communication rules that provide a method for conducting on-line (from one point to another) communications. In most cases, you'll use PPP to connect to a UNIX host or the Internet, or to enhance your Dial-Up Networking capability.

program information file See PIF.

protected mode The processor mode in which the processor can access all of extended memory. This mode also provides a better level of application error detection as part of the processing cycle.

protected-mode mapper A special application that converts real-mode device driver calls into those used by a protected-mode counterpart. It enables you to use your DOS drivers under Windows. Without the support of this VxD, Windows couldn't support legacy devices that lack Windows-specific drivers.

RAID (redundant array of inexpensive disks) One method of hard disk error recovery that relies on two or more hard drives working in unison. Each drive contains part of the data required to re-create the entire data set. The data is striped onto each drive and is followed by error-correcting bits. If one drive fails, the data can be reconstructed on a new drive using the contents of the other drives in the array.

RAS (remote access server)

raster font A type of font that relies on a bitmap to define its characteristics. The advantages of using this font type are speed of printing and precise definition. Disadvantages include huge disk space requirements and the inability to resize the font.

real mode A Windows operating mode that supports the capabilities of the 8088/8086 processor. This essentially limits you to loading one application within the confines of conventional memory. Windows versions after 3.0 don't support this mode. You must use these versions with workstations containing an 80286 or higher processor.

redundant array of inexpensive disks See RAID.

REG file A special file used by the registry to hold a text version of the keys and values it contains. Some applications provide REG files you can use to incorporate their file associations and OLE capabilities into Windows.

registry key This is a registry heading. It provides the structure required to hold configuration values and other information required by Windows and the applications it runs.

registry value Each value provides some type of Windows configuration information. Three types of registry values exist: string, DWORD, and binary. Of the three, the only human-readable form is string.

remote access The capability to use a remote resource as you would a local resource. In some cases, this also means downloading the remote resource to use as a local resource.

remote procedure call See RPC.

RPC (remote procedure call) The capability to use code or data on a remote machine as if it were local. This is an advanced capability that will eventually pave the way for decentralized applications.

SCSI (Small Computer System Interface)

SCSI manager Windows NT introduced something called the miniport driver. With Windows 95, you can use the Windows NT miniport binaries. Before you can actually do this, however, Windows 95 must translate its commands to a format the miniport driver will understand. The SCSI manager performs this service.

SCSIzer A file subsystem component that deals with the SCSI command language. Think of the command language as the method the computer uses to tell a SCSI device to perform a task. The command language isn't the data the SCSI device handles; instead, it's the act the SCSI device will perform. There's one SCSIzer for each SCSI device.

Security Identifier See SID.

server An application or workstation that provides services, resources, or data to a client application or workstation. The client usually makes requests in the form of OLE, DDE, or other command formats.

shell extension A special application that gives some type of added value to the operating system interface. In most cases, the application must register itself with the registry before the operating system will recognize it.

SID (security identifier) The part of a user's access token used to identify the user throughout the network; it's like having an account number. The user token the SID identifies tells what groups the user belongs to and what privileges the user has. Each group also has a SID, so the user's SID contains references to the various group SIDs that he belongs to rather than a complete set of group access rights.

stripe set One disk within a redundant array of inexpensive disks (RAID) setup.

SVGA (super video graphics array)

system resource Data, peripheral devices, or other system components used to create, delete, or manipulate documents and produce output.

system VM (virtual machine) The component of the Windows operating system tasked to create virtual machines and manage DOS applications.

TAPI (telephony API) An interface used by applications to interface with various types of communications equipment. This currently includes both modems and fax devices.

task switching The capability of an operating system to support more than one application or thread of execution at a time. The foreground application or task is the only one that executes. All other threads of execution are suspended in the background. Contrast this with multitasking, in which all threads—background and foreground—execute.

TDI (Transport Driver Interface) Virtualizes access to the network protocol under Windows. This is the reason that more than one virtual machine running on a system can access the network drives at the same time.

telephony API See TAPI.

Terminate-and-stay-resident program See TSR.

Thread One executable unit within a Windows application. Running an application creates a main thread. One of the things the main thread does is display a window with a menu. The main thread can also create other threads. Background printing may appear as a thread, for example. Only 32-bit applications support threads.

thunk The programming interface that translates 32-bit data and system calls to their 16-bit counterparts. The opposite translation takes place going from a 16-bit application to its 32-bit counterpart.

Transport Driver Interface See TDI.

TrueType A special form of vector font originally provided with Windows but used with other operating systems as well. This vector font provides hinting and other features that give it a smoother appearance on-screen.

TSD (type-specific driver) Part of the file subsystem, this layer deals with logical device types rather than specific devices. One TSD handles all the hard drives on your system, for example, and another TSD handles all the floppy drives. A third TSD would handle all network drives.

TSR (terminate and stay resident) An application that loads itself into memory and stays there after you execute it. The program usually returns you directly to the DOS prompt after loading. Pressing a hot-key combination activates the application, allowing you to use the application. In most cases, TSRs provide some type of utility, print spooling, or other short-term function.

type-specific driver See TSD.

UAE (unrecoverable application error) A processor or memory error that occurs when an application makes a request the system can't honor. The operating system normally doesn't detect an error of this type. The result is that the system freezes or becomes unstable to the point of being unusable. See also GPF.

UMB (upper memory block) The area of memory between 640KB and the 1MB boundary. IBM originally set aside this area of memory for device ROMs and special device memory areas. Using various memory managers allows you to load applications and device drivers in this area.

unrecoverable application error See UAE.

upper memory block See UMB.

USB (Universal Serial Bus)

VBA (Visual Basic for Application) A scripting language standard from Microsoft designed to replace DDE. It uses functions and commands that a server application makes available to a client application to exchange data.

VCPI (Virtual Control Program Interface) A method of accessing extended memory from a DOS application using a third-party XMM. See also DPMI.

VDD (virtual display driver) Windows 3.x used this module as its sole source of communication with the display adapter. Windows 95 provides it for compatibility purposes and for DOS applications. It translates application requests into graphics commands and draws the result in video memory.

VDM (virtual DOS machine) Essentially, a single copy of a DOS machine created in memory. This machine provides all the access features of the real thing, but it doesn't physically exist. Windows NT places each DOS application in its own VDM. The reason is simple: To provide the higher level of system reliability Windows NT users demand, Microsoft had to make sure that each application had its own environment—an environment completely separate from that used by every other application. It's also important to remember that 16-bit Windows applications share one VDM. You need to remember that Windows NT always starts a VDM and then runs a copy of 16-bit Windows in it to service the needs of 16-bit Windows applications. This effectively adds two layers to every interaction: one for the VDM and another for the WIN32 subsystem. As with everything else, this additional layering is transparent to the programmer. You still use the same interfaces as before.

vector font A type of font that uses mathematical expressions instead of a bitmap to define its characteristics.

vector table The place in lower memory where ROM and DOS store pointers to operating system-specific routines. Most of these routines allow an application to access a device or to perform some specific task, such as opening a file.

VESA (Video Electronics Standards Association) A standards group responsible for creating display adapter and monitor specifications. This group has also worked on other standards, such as the VL bus used in some PCs.

VFAT (virtual file allocation table) An enhanced method of disk formatting based on the FAT system. It allows for additional functionality, such as long file names.

Video Electronics Standards Association See VESA.

virtual anything driver See VxD.

Virtual Control Program Interface See VCPI.

virtual display driver See VDD.

virtual DOS machine See VDM.

virtual file allocation table See VFAT.

virtual memory manager See VMM.

Visual Basic for Application see VBA.

VMM (virtual memory manager) The part of the Windows memory manager responsible for creating and maintaining the swap file on disk. The swap file contains data that can no longer fit in memory and makes it appear that you have more memory under Windows than physical memory will support. The VMM also takes care of the actual task of swapping data between disk and physical memory as applications request specific data.

volume tracking driver See VTD.

VRAM (dual-ported video RAM) A special form of memory that allows simultaneous reads and writes. It provides a serial read interface and a parallel write interface. The advantage of using VRAM is that it's much faster and doesn't require as much detection code on the part of the application or device driver.

VSD (Vendor supplied driver)

VTD (volume tracking driver) This file subsystem component handles any removable devices attached to your system.

VxD (virtual anything driver) A special form of DLL that provides low-level system support.

Windows NT file system See NTFS.

wizard A specialized application that reduces the complexity of using or configuring your system. The Printer wizard, for example, makes it easier to install a new printer.

WUGNET (Windows Users Group Network)

WYSIWYG (What You See Is What You Get)

XMS (eXtended Memory Specification) The original version of this specification (developed by Quarterdeck) appeared in 1986. It allowed an 80286 or above processor to access up to 64KB of extended memory from within the conventional memory area by enabling the A20 address line. The overall effect of this specification was to allow multitasking from within DOS by freeing more application memory. In 1990, Microsoft revised its HIMEM.SYS driver with the release of Windows 3.0. The scope of XMS memory was increased to include all of extended memory. The new release of Windows could use all of extended memory to multitask Windows applications. Microsoft also established new terminology for all memory above 640KB: upper memory blocks (UMBs), high memory area (HMA), and extended memory blocks (EMB).

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