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NOTE:  Items highlighted in RED are defined elsewhere in this Glossary, while items highlighted in BLUE are site links for further information.


JACK:  A common term for a “wall jack” for telephone or computer connections.  Sometimes caled a module or punch down block.  See also RJ (“registered jack”).

JACKING:  Stealing.  Used in various contexts.  For example:  Hijacking, or stealing someone’s computer or internet connection for nefarious use (stealing confidential information, creating a botnet, etc.).  Sidejacking, the act of hijacking an engaged web session and using the valid user’s credentials to connect to a server.  Sheepjacking, the use of a program called Firesheep to hijack someone’s unencrypted WiFi sessions with a single click.  Then, there’s clickjacking, a malicious technique of tricking Web users into revealing confidential information by getting them to click on innocuous web pages that are not real, but intended to direct them to malicious pages.  Like pagejacking, which is where the malicious user actually copies the pages of a real website, but creates a rogue copy, so that when a user clicks on the link, he is directed to the malicious, not the correct, website, to his detriment.  Finally, there’s juicejacking, the use of various mobile phone charging kiosks and services to be found in hotels, shopping centers and airports, where you can plug in to a charger, but which may also be modified to steal the data from your device.  See SPYWARE for more.

JAGGIES:  Refers to the visible jagged “steps” around the edge of a digital image that result as the image’s resolution is decreased.  The technology of anti-aliasing is used to reduce this occurrence.


JAILBREAK:  This term is primarily used to refer to the process of hacking an iPhone in order to free it from Apple restrictions.  By doing so, you would be able to use the phone with any carrier (not just AT&T) as well as use apps created companies other than Apple.  Of course, it will void your Apple warranty, may open you up to viruses and could turn your iPhone into a “brick” (a useless lump of phone).  Cydia and Installer are the unofficial “App Stores” of the jailbreak subculture. For a discussion about tethering, unlocking and jailbreaking, see PHONES.

JAMMER:  A device used to block signals from cell phones and other electronic devices (including things like cell signals, Wi-Fi, Bluetooth, satellite radio, GPS), so that they cannot send and receive transmissions.  While you would like to go to a restaurant, theater or office and surreptitiously use a scanner to quietly enjoy your meal or movie, it’s illegal for individuals to sell, buy or use one (assuming you build your own, I suppose).  In the U.S., only law enforcement is authorized to use such devices, although you can find them for sale on the Internet. They need to be able to block signals like cell phones which may be used to remotely detonate terrorist explosive devices.  They’ve also legitimately been used quite often, for example, with permission from law enforcement, in schools and colleges to prevent possible exam cheating using mobile phones.   CTC has some 285 models on sale, and even claims that some were “approved by the FCC” which was absolutely not true.  This is because jammers interfere with connections for 911 calls or first responders which must communicate in medical and other emergencies, creating a direct danger to public safety.   The FCC is continually issuiJammerng fines for unlawful use of jammers, such as fining one man $48,000 for using one while on a highway.  In 2014, the FCC issued its largest fine against Chinese electronics vendor CTS Technology, a record $34.9 million, ordering it to stop selling signal jammers that interfered with wireless communications.  More important, the FCC also ordered CTS to provide records of those who purchased the device from them, supposedly so it could fine the purchasers and users as well.

JAVA vs JAVASCRIPT:  This can be confusing, because both have similar names, both work inside HTML adding interactivity to web pages, and both share some of the same commands and language elements.  But Javascript is deployed differently from Java and serves a different purpose.  JavaScript started as a small language with which a programmer can create web page elements like buttons, which can move and change when selected, as well as other elements like menus and interactive features.  But the key is that, unlike the full Java programming language, JavaScripts cannot stand alone outside of the web pages encompassing them.  Java itelf is a complete stand alone programming language that can be used to create complete stand alone apps. By the way, note that it is Java, not JavaScript, that was vulnerable to malware attacks, such as those well publicized in early 2013 (Java is now frequently updated to prevent this).  While used with millions of devices, it is not as prevalent in web development as it used to be and is not always necessary on every PC.

Jave logoJAVA:  A programming language (series of computer instructions) introduced by James Gosling (Canadian computer scientist, formerly a Louisiana Sheriff) at Sun Microsystems in 1995 (now owned by Oracle) that enables developers the freedom to write software code on one platform (think Linux, Unix, Windows, etc.) and run it on another. It was dubbed the “write once, run anywhere” programming software which is still popular 20 years later, boasting over a million developers which use it primarily for building client-server web applications.  (See Programming for a brief example.)   It is popular on the Internet as it allows programmers the freedom to create small programs called applets to run within a web browser to complete tasks for automating on-line stores, processing forms, etc.  Increasingly, though, most websites rely on Flash rather than Java.  Java is foundDuke Java mascot on 3 billion devices (they claim) such as mobile phones, routers, printers, parking meters, public transportation passes, cable boxes, blue ray disk players, set-top boxes and cars and many other devices, in addition to computers.  The Java mascot is named “Duke”  (see right); a new Duke Duke with guitarpersonality is created each year, such as Duke playing guitar, with a jetpack, etc.  Unfortunately, Java has often been a security risk, allowing malware to get into your computer.  In Jan 2013, Oracle even recommended that it be disabled until a patch could be created.  Don’t confuse Java the program used to create applications from Java Script, the scripting code within web pages (see below).  The most current version, Java 8, was officially released on 3/18/14. Even though Java is quite effective, some programmers just don’t like it.  For them, there are lots of other languages that compile to Java “byte-code” and run on the Java Virtual Machine (“JVM”).    Languages like Jython, JRuby, Scala and Clojure all run on top of Java.  Other languages, such as Perl, CGI or PHP can perform many of the tasks done by Java, but they were developed for scripting and quick evaluation of programs and don’t have the power and depth offered by Java.

JAVA ANON PROXY, A/K/A jap A/K/A/ JonDonymA proxy system for pseudo-anonymous web browsing, sending requests through multiple data streams and cascades to obfuscate the data to outsiders.

JAVAFX:  A rich internet application introduced by Sun Microsystems in 2007 originally intended for mobile web development.  But iOS, Android and HTML 5 have pretty much taken over this area and Java 8 has many of these capabilities.

JAVA CARD:  See Smart Card.

JAVA RUNTIME ENVIRONMENT (“JRE”):  This is the “sandbox” that Java apps run in.

JAZ:  A brand of data storage diskettes. See Media.

JAVA SCRIPT:  Not the same as Java (above), Java Script originated at Netscape, was created by Brandon Eich, enabling much faster website development and is interpreted at a higher OSI level than Java, is somewhat easier to learn than Java, but lacks the portability and speed of Java.  It’s a subset of the full Java and is coded inside HTML documents so it can run without having the full Java installed on a PC. The original purpose of the scripts were to make an icon move (“make the monkey dance”) when a user moved the mouse over it, but it has become increasingly more complex.  See also Google Dart.  The next step up from JavaScript is Ajax, which improved Java by allowing the code to be built directly into a web page, not just a document.

JBOD:  A derogatory acronym for SPANNING, which stands for “Just a Bunch of Drives (or Disks),” as opposed to hard drives that have been configured to RAID, to increase fault tolerance and improve data access performance.

Jelly logoJELLY:  An experiment funded by Twitter founder Biz Stone, which was introduced in late 2013.  It is a mobile Q & A service (see Lazyweb) onto which users post questions onto a blog for answering or comment.  It doesn’t really add anything new to the blogosphere.  We’ll see if it lasts. 

JIFF:  (Pronounced “jiff,” like the peanut butter) is a popular graphic file format.  It is pronounced differently from “Giff”  (with a hard “G”), another popular graphic file format.  See also, jpg, below.

JITTER:  A measure, usually in milliseconds (ms), that determines whether a connection signal fluctuates such that it is out of sync, which can cause a significant problem with certain apps like VoiP.  Usually, if jitter is within 20ms - 30ms, it is considered acceptable.

JOIN:  Used in relational database management systems (“RDBMS”), this term means to match one table (the “inner” join) against another (the "outer” join) to create a third based on a matching condition in both. For example, a join showing all red sports cars (inner) which received speeding tickets (outer) would, if there any (condition) produce a third table of the results.

JOLLA:  A smart phone developed by a Finnish company founded by former Nokia employees, running it’s own Sailfish operating system, which is expected to launch in late 2013 and compete with Android and Apple.

Joost logoJOOST:  The major competitor to, it is an Internet TV service, created by Niklas Zennstrom and Janus Friis (also the founders of Skype and Kazaa) with investors such as CBS, Viacom and Sequoia Capital, among others.  Like Hulu, it is also a name with no English (or Danish) translation, but unlike Hulu (see definition), the founders chose Joost because they just liked the ring of it.  Some people suggest that the name suggests ‘juiced” as in “Free TV Has Juiced the Internet” (whatever that actually means). 

JOULES:  A standard measurement of electrical energy (power) used in determining a triggering  threshold for surge suppressors.  See, SURGE SUPPRESSORS.  If you must know, one joule is the equivalent of one watt of power radiated or dissipated for one second or the amount of energy exerted when a force of one newton is applied over a displacement of one meter.  Is that clear?  It is named after English physicist James Prescott Joule (1818-1889).

JOURNALING:  A file system that keeps track of the changes it intends to make in a journal that can be accessed in the event that the changes are interrupted before they are completed.

JOYSTICK:  An gaming input device (also called a “controller”) which substitutes for a keyboard and mouse, commonly used to control video games on a computer.  ThJoysticke device consists of a base and a vertical stick which can be moved in virtually any direction, slowly or quickly, to achieve far greater control than other types of input.  Exactly like a helicopter steering column, which it sometimes emulates in games.  Some joysticks also have buttons to control other features, such as a trigger on the stick for shooting.  Joysticks typically connect to a computer using serial or USB port connections, and sometimes have special software to control the device and the various feature buttons.  The derivation of the term is fairly obvious - the exhilarating feeling of joy that comes from its use!

JPG: Also JPEG.  A popular file format for graphics, because of its ability to compress a file for transmission over the Internet, although there is some loss in quality.  This is called “lossy,” and it means that more quality is lost each time a .jpg is edited and saved because when it is saved, .jpg artifacts are added so that the colors are not accurate.  You can post a graphic, particularly a thumbnail, at anywhere between 60 and 150 dpi and it’ll look just fine; anything more won’t show appreciably better, due to the monitor limitations.  (Printing, however, is another thing.) Stands for Joint Pictures Expert Group.  Sometimes, however, called a “dirty .jif” because, when it compresses the file, it also reduces its resolution.  Remember: You can reduce the size and resolution of a graphic by making it smaller and less dense, but you can’t go backwards and make it larger, as it will look jagged and unclear.  TIP:  Always keep the full size original of a graphic and, if you’re going to reduce its size or resolution, save the edited version as a separate file.  And don’t repeatedly edit and save it. 

[Other popular graphic file formats include: .gif, .jif, .bmp, .png, and .tif.] Each of which has its own benefits and detriments.  For example, the best picture quality is with .tif or .png, the maximum compatibility is with .tif or .jpg, smallest file size is, of course, .jpg and the worst choice is 256 color .gif.

Also, see Speeds and Storage Sizes for a side-by-side comparison showing how the image format affects file storage size. And, for a comprehensive article detailing image and photo formats, click HERE.

JUICEJACKING:  See “jacking.”

JUMPER: A tiny plastic connector box that can be placed over pairs of pins on computer circuit boards or hardware components such as drives (see right) that connects them electronically.  For example, the master, slave, and cable-select selections on the back of a hard drive or CD-ROM.  For more info, click HERE to go to the hard drive page.

JUMP LISTS:  A feature introduced by Microsoft sJump Listtarting with Windows 7 which lets users create lists of recently opened files, folders, websites and other items, all organized by the program that is used to open them.  Jump list items can be created by dragging a file icon or shortcut from the Start Menu to the desktop or a task bar.  An example of a jump list is shown to the right: 





























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