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Z is the electronic signal for impedance. We have several pages that deal with impedance on our Electronics Calculators, Converters and Tables menu.


Z39.50 is a generally accepted and widely used standard communications protocol for the search and retrieval of bibliographic data in online databases. Z39.50 is used (mostly by the academic communities) on the Internet to search the Online Public Access Catalogues (OPAC) of library holdings. It is also sometimes used to link disparate OPACs into a single unified OPAC. Z39.50 is an American National Standards Institute ANSI/NISO standard. There are many of these worldwide; here is one from the Vatican Library.


The premier 8 bit processor chip of the early days of microprocessors. Made by Zilog, it used a "reverse" Intel 8080 assembler set but was for all practical purposes a better mousetrap and the world beat a path to Zilog's door. The subsequent offerings from Zilog, the Z800 and Z8000 were directly competitive to the Intel 8085 and 8086; we all know who won that war, especially since you probably never have heard of the Z800 or Z8000. The Z80 was and is ideal for embedded control applications. (A great percentage of TV remote control units use Z80s as the brain.) The Z80 architecture incorporates dual register banks that enable fast context switching and interrupt handling. Discover why this microprocessor is still receiving praise from engineers worldwide even after its initial 1974 introduction. Check the Z80 out at HTTP://WWW.ZILOG.COM.


The Zilog hybrid offering to be competitive to the 8086 from Intel. The instructions were backward compatible with the Z80. Since you have never heard of it (I'm pretty sure of that), it is obvious who came out on top. Check the Z800 out at HTTP://WWW.ZILOG.COM.


The effort of Zilog to get back into the competitive PC processor business. Though it was based on the very popular Z80 instruction set, it was too little too late. Check the Z8000 out at HTTP://WWW.ZILOG.COM.


A term (verb) used to indicate electrically damaged hardware or media, such as a zapped diskette, zapped memory or zapped computer. This more often than not refers to static electricity as the culprit. In programming, the term zap (noun) is a precise and immediate correction for a computer code problem. Most proprietary software programs are distributed to customers as compiled code in the form of an unreadable binary string of computer bits. When a bug is detected after the software is released, the only way to fix the already compiled code is to overlay the imprefect or buggy code with a sequence of corrected code. This overlaying is known as zapping (verb) and the fix itself is a zap. IBM provides its mainframe software customers with a special program for applying zaps that is called SuperZap. (For the support fees they pay, it should be SSZ (Super SuperZap). In generic computing, to zap (verb) can also mean to erase or get rid of something. On a Mac, to "zap the PRAM" is to erase PRAM so that the system can rebuild its contents. See patch.


Short for Zero Administration for Windows, a collection of utilities developed by Microsoft that should enable administrators to centrally manage and update software on PCs connected to a LAN. ZAW was developed partly as a response to the emergence of Net PCs. One of the main selling points of Net PCs is that they enable software to be centralized, which greatly simplifies administration of applications. ZAW attempts to offer the same sort of administration ease while letting the applications remain on traditional desktop PCs. Currently, ZAW is more specification than reality (anyone who has used Windows knows that...), but it is expected to be part of both Windows NT 5.0 and Windows 2000. W95 and W98 never quite made it. Update 2/15/2002; it didn't make it into 2000 or XP either!


An acronym for Zero Byte Time Slot Interchange, used in conjunction with definitions regarding DS1 coding schemes such as B8ZS.


1. An algorithm used in 3-D graphics to determine which objects, or parts of objects, are visible and which are hidden behind other objects. With Z-buffering, the graphics processor stores the Z-axis value of each pixel in a special area of memory called the Z-buffer. Different objects can have the same x- and y-coordinate values, but with different z-coordinate values. The object with the lowest z-coordinate value is in front of the other objects, and therefore that's the one that's displayed. An alternate algorithm for hiding objects behind other objects is called Z-sorting. The Z-sorting algorithm simply displays all objects serially, starting with those objects furthest back (with the largest Z-axis values). The Z-sorting algorithm does not require a Z-buffer, but it is slow and does not render intersecting objects correctly. Please see buffer, memory and memory buffering.
2. The "German" way to pronounce what you do at "Z-gym".


An acronym for Zoned Constant Angular Velocity. See (CAV).


An acronym for Zoned Constant Linear Velocity. See (CLV).

z coordinate

A Z coordinate is the third-dimensional coordinate in a volume pixel, or voxel. Together with X,Y coordinates, the Z coordinate defines a location in a three-dimensional space.

ZDL or Zero Delay Lockout

Technology designed to prevent beaconing stations from entering into a Token Ring by locking out faulty stations.


ZDNET is the web site of Ziff Davis. It contains great sources of industry information and useful utilities. Check it out at HTTP://WWW.ZDNET.COM.


A special type of voltage regulating diode. This type of diode conducts in the reverse direction from normal diodes, in other words from cathode to anode. To pass electricity through a Zener diode, it must be around eight to ten times the value of the normal diode, typically 4.7 volts. In normal operation a Zener can act as a signal filter, since electrical interference is usually too weak to get through it.
You might want to see our circuit for building a Zener tester and also our Zener diode calculator.


The metric prefix for the American system value of negative one sextillionth or 10 to the -21st power, (-1,000,000,000,000,000,000,000). See the inverse, zetta, as in zettabyte.


1. The arithmetic symbol, 0, representing no magnitude.
2. One of the two binary digits (bits), the other being one, 1.
3. To set something to the value of zero.
4. To fill or replace with zeros, often called zero filling.

zero code suppression

Line coding scheme used for transmission clocking. Zero code (line) suppression substitutes a 1 in the 7th bit of a string of 8 consecutive zeros.


The process of calibrating a meter so that it shows a value of zero (0) when zero is being measured. This process must be done to insure accurate readings during the test session.

zero-page addressing

An addressing mode in which the address is given as an unsigned binary number that specifies one of the memory locations between 0 (zero) and 256 (decimal).

zero-slot network

A network originally named to indicate a serial or parallel connected configuration; one that did not use NICs. Some machines now have slots available but have network chip interfacing built into the motherboard. Currently, the same name is applied to specially made computers within keyboards that do not have any add in bus. All the network technology is on the multi-purpose keyboard/mainboard. Originally, these networks were much slower than NICs but they are comparable in interfacing speed now. They have NO (zero) expandability.

zero wait state

A condition where memory is operating at the fastest speed possible. It is where in the repetitive course of operation of fetching and yielding data, there are no (zero) "no-op" cycles, normally called wait states. Memory expects the data to be in the buffers when it goes to get the data. In a wait condition, after the memory gets the command to fetch data, it will wait for one, two or more cycles to assure that the data has been placed into the buffer properly before it tries to get it.


In non-technical terms, this is "big bytes"; in the American system, it is called sextillion. In more formal and definitive terms (just how big is this?), it is 2 to the 70th power bytes (2^70 = 1,180,591,620,717,411,303,424), which is approximately 10 to the 21st power (you knew that didn't you) bytes (1,000,000,000,000,000,000,000). A zettabyte is equal to 1,024 exabytes. ("That's a big help", you say...) The name zetta was chosen because it's the last letter of the Latin alphabet and also sounds like the Greek letter Zeta. That is very important since all of this is Greek to most people anyway. Why do we need such a number anyway? A good example is that this is the amount of storage space needed on your hard disk to handle the expenses in your checkbook program while your kids are going through school. See zepto, the inverse of zetta; often called "Out-Of-Control!" Need to convert designations of memory? Don't know your KB from your MB? Try our memory and storage converter. (Also see powers of ten, kilobyte, megabyte, gigabyte, terabyte, petabyte, and yottabyte.)


ZIF is the acronym for Zero Insertion Force, a technology used in motherboard and CPU sockets. They permit the easy insertion and removal of chips with large numbers of easily bendable pins. The technology began on 486 sockets and continued through the Pentium II in the Intel line compatibility. A clamping lever is used to remove and apply contact force on the pins of the CPU. The ZIF interface evolved through eight variations, each with a differing number of pins and pin layout arrangements. Currently, the best-known is Socket 7, the configuration used in the Pentium microprocessor. However, the Pentium Pro uses Socket 8. With the Pentium II microprocessor, which is based on Intel's new P6 micro architecture, Intel has changed to a new connection configuration called Slot 1 and Slot 2. In this configuration, the microprocessor comes packaged in a cartridge that fits into a 242-contact or 330-contact slot in the motherboard. AMD and Cyrix, which offer competitive processors, continue to use the Socket 7 arrangement.


A microprocessor giant that fell by the wayside. They invented and put into actual use the Z80, the world's best selling 8 bit microprocessor. That CPU was the standard of the 70's and 80's and had the CPU world at its feet until Intel brought out the 8085 and 8086 series of processors. A better marketing push from Intel and Zilog, Inc. was an afterthought in 16 bit and greater processors. Zilog's offerings, the Z800 and Z8000 fell far short. Co-founded in 1974 by industry trailblazers Federico Faggin and Ralph Ungermann, ZiLOG Inc. is engineering its own recovery and survival under the leadership of current Chairman, President and CEO Curtis J. Crawford. It remains to be seen if they can move away from the niche they are surviving in, the control microprocessor market, and be competitive in the computer CPU market again. Check them out at HTTP://WWW.ZILOG.COM.


The term zine is short for "electronic magazine" and for the even shorter term "eZine". "E-zine" and "e-Zine" are spelling variations. A similar term is "ejournal." There are several usages of the term ezine. The term is similar to zine, an earlier usage in print media that derived from magazine and described "small press" or personally distributed magazines or newsletters.
1. An early use of the term ezine on the Internet arose to describe a new kind of Web site that contained a mixture of content (articles, pictures, poetry, fiction, and comment) and style conveyed in a way that exploited and celebrated the Web as a new information medium. Examples include Salon and HotWired.
2. Some ezines are not so interested in the Web as an expressive medium in itself but as an opportunity to reach an audience electronically (and therefore more economically than with the print medium). As a result, hundreds of Web site ezines have been invented, each devoted to a special cause, subject, or sensibility. See John Labovitz's E-Zine-List. This kind of ezine (along with the E-Mail newsletter mentioned below) is roughly the cyberspace equivalent of the printed zine (and, when printed out, is, in fact the equivalent).
3. The term is also used to describe any electronic magazine, including those of print magazines such as National Geographic and Newsweek that have electronic editions. Thus, E-Zine Database includes both electronic-only magazines together with electronic-edition magazines.
4. The term also sometimes includes E-Mail published newsletters, of which there are thousands that can be subscribed to. Some of these refer to themselves as zines or ezines.


1. Zip is a standard accepted term for a DOS compression utility used to create files to .ZIP archives. There are also Windows versions of this architecture; not all are from the original PK company. PKZip is the original compression utility. (See PKUnzip.) The resulting files are called .ZIP files and end in the extension .ZIP; there are many companies now producing utilities that do this work and recognize this file type. The main purpose of this architecture is to reduce the file size and quantity into one much smaller file that is easily transmitted across a network with all the supporting files incorporated within. Speed for the user and reduced network or Internet traffic are the ultimate goals. See zipping.
2. This is also the name of a particular removable storage drive that hold about 100MB of data per diskette, or 250MB, depending on the model. The ZIP diskettes are slightly larger than standard diskettes in physical size. The ZIP (disk and drive) technology is owned by Iomega. They also have a backup storage technology called JAZ. They have bordered on financial disaster for some reason for the past couple of years but have recovered and are located at The Official Iomega Site. A second source for additional non-company based support on all the Iomega technology is The Unofficial Iomega Page. A similar but competitive technology for the removable drive is called SuperDisk, which holds about 120MB of data per disk, but also reads and writes standard diskettes in the same drive. The company that owns that technology is Imation. The SuperDisk has never really caught on.
3. An acronym for Zone Information Protocol. The AppleTalk session layer protocol that maps network numbers to zone names. ZIP is used by NBP to determine which networks contain nodes that belong to a zone.


3COM ASIC product and technology that streamlines cell-based switching by converting Ethernet packets to ATM sized cells and switching them at over 780,000 cells per second. The ZipChip, used in the 720x interface cards for the CELLplex 7000, the LinkSwitch 2700 and other Ethernet/ATM switches, combines with onboard RISC processors to boost aggregate bandwidth.

Zip Code

ZIP code is an acronym for Zoning Improvement Plan. These numeric codes are postal codes in the United States that identify preassigned geographic boundaries and make mail sorting and delivery more efficient. The original specification was a five digit numeric code for the United States. (If you would like to find where a zip code is and other information about the area, use our US Zip Code Lookup.) Other countries have similar designations, usually referred to as post codes or postal codes. The idea and technology were actual critical nightmares for data processing people worldwide when the idea was expanded to Zip+4, yielding a nine digit Zip Code. We wrote the first code for the U. S. Post Office for that change.

zip drive

1. ZIP drives are a brand and type of floppy type technology. See zip and Iomega.
2. The CSG Zip Drive is a Chevy S-10 service vehicle. See the CSG Zip Drive Story here.


1. Zipping is the process of packaging a group of files into a single file or archive that is called a zip file. Usually, the files in a zip file are also compressed so that they take up less space in storage and take less time to send to someone. Several popular tools exist for zipping such as PKZip in the DOS operating system, WinZip, CCZip and NetZIP in Windows, MacZip for Macintosh users, and Zip and UnZip in UNIX systems. The result of zipping is a single file with a ".zip" suffix. Most zip files compress the included files. After you download or otherwise receive a zip file, you can extract (and, if necessary, uncompress) the original files before using them. Most software that you download from the Internet will arrive as a zip file. Typically, by double-clicking on a self-extracting zip file, it will automatically extract and store the individual files. One of these files is usually called the "setup.exe" file. Double-clicking on this file will cause the software to be installed as a selectable program in your operating system.
2. The speed that you feel your computer is moving after getting away from a dial-up Internet connection to any sort of DSL or cable connection.

ZIP storm

A network broadcast storm that occurs when a router running AppleTalk propagates a route for which it currently has no corresponding zone name. The route is then forwarded by any and all downstream routers, and a ZIP storm ensues.


The acronym for Zone Multicast Address. A data-link-dependent multicast address at which a node receives the NBP broadcasts directed to its zone.


A file transfer protocol based on X-Modem, Z-Modem was designed (along with Y-Modem) by Chuck Forsberg to add batch transmission, and variable data block size. It was considerably faster than Y-Modem and had better error checking capability. A particularly popular, fast and accurate method of modem to modem communication, used heavily by BBS services not on the Internet. It is correctly termed a data transfer protocol. It has excellent error correcting capability and support large blocks of data, 512 bytes, compared to other similar functions of the time. An advanced form of CRC was the error detector. See Also X-Modem and Y-Modem.


In the language of computing slang, the term zombie has many meanings. Such as:
1. A user that surfs the web hours on end and never seems to sleep or tire.
2. On the Internet, a zombie is an abandoned, unkept or sadly out-of-date Web site. It can also refer to the residue of a site that for some reason has been moved to another Web address. It's a ghost site that appears to have moved. Zombies contribute to linkrot, a term for dead end links.
3. In at least one form of Internet denial-of-service attack, one or more insecure Web servers are compromised by hackers who place code in each Web server that, when triggered, will launch an overwhelming number of requests toward an attacked Web site. This process of abusive use which will soon leave the server unable to service legitimate requests from its users. A compromised Web site that is used as an attack launch point is known as a zombie.
4. In the UNIX operating system world, developers sometimes use the term to refer to a program process that has died but hasn't yet given its process table entry back to the system. This process has evolved into the NT and W2000 worlds as well. While the same type of action happens in Windows 98, the result is called "dead meat" as the process is NOT recoverable. Microsoft terms it a Fatal Error.


1. An area under a particular administrative or other control, for example a domain name is a zone in the name server configuration. Generally a zone can be further divided into sub-zones with authority delegated to their own administrators and servers.
2. A collection of all terminals, gateways, and multipoint control units (MCUs) managed by a single gatekeeper. A zone includes at least one terminal, and can include gateways or MCUs. A zone has only one gatekeeper. A zone can be independent of LAN topology and can be comprised of multiple LAN segments connected using routers or other devices.
3. In AppleTalk, a logical group of network devices.
4. A segment or area of the world with relationship to time. To see UTC in relationship to other time zones, check out Time Zone Converter.


1. A compression and archiving format made popular on the Amiga system, zoo is available in public domain executables for most major operating systems.
2. The work area for many programmers.
3. A Web site that holds collections of Internet viruses. These sites may be illegal in certain countries; in those that they are not, they should be. This sort of site is only a source of trouble.


In graphical user interfaces (GUI), to make a window larger or smaller. Typically, there is a zoom box in one corner of the window. When you select the zoom box the first time, the system expands the window to fill the entire screen. (This is sometimes called maximizing.) When you select it again, the window shrinks to its original size. (This is sometimes called restoring.) Many applications also provide a zoom feature, which enlarges or reduces the view of an object enabling you to see more detail.


Zope is an acronym for Z Object Publishing Environment. It is a Web site builder and application server that uses the idea that it is serving (or "publishing") objects rather than merely providing content that will be added to a Web page. Zope's proponents believe that it is competitive with site builders and application servers such as ColdFusion and the Netscape Application Server. Zope is public domain, free software, with open source code. Zope calls itself "object publishing software." It claims that users are interacting directly with "real objects" rather than with dynamically updated files that are being served. Zope consists of a "publisher" that publishes the objects using Zope's Persistent CGI protocol; a framework for the folders, files, and images that Zope views as "built-in objects", an object database, a template for dynamic Web page generation, and SQL methods and database adapters so that Zope can interact with data in popular database servers, such as Microsoft's SQL Server. By default, Zope's object database uses the operating system's file system to manage data. However, it can also work with relational database management systems. Specifically, Oracle, Sybase, MySQL, INFORMIX and ODBC are supported. Zope was created by Digital Creations and is being used by the U.S. government, over 80 regional U.S. newspapers, and some other companies. The software is written in Python, an interpreted, interactive, object-oriented language similar to Java, with small pieces written in C for better performance. Web site developers using Zope do not need to know or use Python, however. Zope runs on all major operating system platforms. See more at HTTP://WWW.ZOPE.ORG.

Zulu time

Zulu time is used in the military, navigation, computing and telephony generally as a term for Coordinated Universal Time (UTC), sometimes incorrectly called Universal Time Coordinated, Universal Coordinated Time or Coordinated Universal Time (but still abbreviated UTC universally), and often called (again, incorrectly) Greenwich Mean Time (GMT). (In the strictest sense, UTC is NOT the same as GMT, as UTC is an ATOMIC time-scale, while GMT (strictly speaking UT1 [UT-one]) is tied to the rotation of the Earth in respect to the fictitious 'mean Sun'. UTC is, however, kept within 0.9 seconds of UT1, by virtue of leap seconds. For those that are not time professionals, it is close enough for daily work. For the professional time person, close (correctly) does not count; it is still wrong.) In military shorthand, the letter Z follows a time expressed in Greenwich Time. Greenwich Time, now often called Coordinated Universal Time, is the time at longitude 0 (zero) degrees 0 (zero) minutes - the prime meridian or longitudinal line that separates East from West in the world geographical coordinate system. This line of longitude is based on the location of the Royal Observatory Greenwich (frequently incorrectly stated as the British Naval Observatory or Royal Greenwich Observatory, though not the same) in Greenwich, England, near London. "Zulu" is the radio transmission articulation for the letter Z. Traditionally, ship and aviation navigation is conducted using Zulu time. Zulu time is usually expressed in terms of a 24-hour clock using the Gregorian time divisions of hours and minutes. To see Zulu Time (UTC) in relationship to other time zones, check out Time Zone Converter. To check the atomic time at the U.S. Naval Observatory, click here. Also check out the Time Zone Information Table.


Short for zoomed video port, a port that enables data to be transferred directly from a PC Card to a VGA type controller. The port is more precisely, a connection to a zoomed video bus. ZV-port is a technology that supports the delivery of full-screen motion video and multimedia to notebook computers. The ZV-port allows special software and a version of the PC Card called a ZV-Port Card to provide a separate dedicated, point-to-point bus or path from continuously arriving video signals directly to the display controller so that they do not need to be handled by the main bus or the CPU, thus saving both time and bus activity. ZV-ports are provided in IBM, Toshiba, and several other manufacturers' notebook computers. With the ZV-port technology, video signals are sent in compressed files using the MPEG standard. The ZV-Port Card intelligently decompresses the files and sends the data directly to the video frame buffer managed by the display controller. The technology can also be used for capturing images sent to the display from a video camera and storing them on a hard disk. Combining user input from the computer's regular PCI bus with the video from the ZV-port, notebook users can play interactive MPEG-based games. This new bus was designed by the PCMCIA to enable notebook computers to connect to real-time multimedia devices such as video cameras. The first notebook computers with the ZV-port arrived in late 1996.

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