Specifications

Glossary
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Jaz drive A proprietary type of removable media
drive with a magnetic hard disk platter in a rigid
plastic case. Developed by Iomega, Jaz drives were
discontinued in 2002, but media is still available
for both 1GB and 2GB versions of the drive.
JEDEC (Joint Electron Devices Engineering
Council) A group that establishes standards for
the electronics industry. JEDEC established the orig-
inal PC66 SDRAM standard.
Joliet Microsoft extension of the ISO 9660 stan-
dard for recordable/rewritable CDs. Joliet is
designed for use with 32-bit Windows versions that
support long filenames, but it supports file/folder
names up to 128 bytes (128 European or 64
Unicode characters) only. Some very long folder/
filenames might need to be truncated when stored
on a Joliet-format CD.
joule The standard unit of electrical energy, it’s
frequently used to measure the effectiveness of
surge suppressors.
joystick An input device generally used for game
software, usually consisting of a central upright
stick that controls horizontal and vertical motion
and one or more buttons to control discrete events,
such as firing guns. More complex models can
resemble flight yokes and steering wheels or incor-
porate tactile feedback.
JPEG (Joint Photographic Experts Group)
The international consortium of hardware, soft-
ware, and publishing interests which—under the
auspices of the ISO—has defined a universal stan-
dard for digital compression and decompression of
still images for use in computer systems. JPEG com-
presses at about a 20:1 ratio before visible image
degradation occurs. A lossy data compression stan-
dard that was originally designed for still images
but also can compress real-time video (30 frames
per second) and animation. Lossy compression per-
manently discards unnecessary data, resulting in
some loss of precision. Files stored in the JPEG for-
mat have the extension
.jpg or .jpeg.
JScript Microsoft’s equivalent to JavaScript. See
also JavaScript.
jukebox A type of CD-ROM drive that enables
several CD-ROM discs to be in the drive at the
same time. The drive itself determines which disc is
needed by the system and loads the discs into the
reading mechanism as needed.
jumper block A small, plastic-covered metal
clip that slips over two pins protruding from a cir-
cuit board. Sometimes also called a shunt. When in
place, the jumper block connects the pins electri-
cally and closes the circuit. By doing so, it connects
the two terminals of a switch, turning it “on.”
Jumper blocks are commonly used to configure
internal hard drives and motherboard settings.
Just a Bunch Of Disks (JBOD) A group of
hard disk drives combined to act as a single vol-
ume. Similar to RAID 0, but the data is spanned
and not striped.
K6 The popular line of Socket 7 and Super Socket
7 processors developed by AMD. Members included
the K6, K6-2, and K6-III.
K56flex A proprietary standard for 56Kbps
modem transmissions developed by Rockwell and
implemented in modems from a variety of vendors.
Superseded by the official V.90 standard for 56Kbps
modems. See also X2, V.90, and V.92.
Kermit A protocol designed for transferring files
between microcomputers and mainframes.
Developed by Frank DaCruz and Bill Catchings at
Columbia University (and named after the talking
frog on The Muppet Show), Kermit was widely
accepted in the academic world before the advent
of the Internet.
kernel Operating system core component.
key disk In software copy protection schemes
popular during the 1980s, a distribution floppy disk
that must be present in a floppy disk drive for an
application program to run.
keyboard The primary input device for most
computers, consisting of keys with letters of the
alphabet, digits, punctuation, and function
control keys.
keyboard macro A series of keystrokes auto-
matically input when a single key is pressed.
keychain drive A popular term for small solid-
state devices using flash memory that connect to a
PC through the USB port. Such devices are recog-
nized as drive letters. Most have a fixed capacity,
but some have provision for upgradeable memory
with SD or other small-form-factor flash memory.
Also known as thumb drives.
Appendix A
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