Specifications

Glossary
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Stateful Packet Inspection (SPI) A technol-
ogy used in firewalls to ensure that all incoming
packets are the result of an outbound request.
stepper motor actuator An assembly that
moves disk drive read/write heads across platters by
a sequence of small partial turns of a stepper motor.
Once common on low-cost hard disk drives of
40MB or less, stepper motor actuators are now
confined to floppy disk drives.
stepping The code used to identify the revision
of a processor. New masks are introduced to build
each successive stepping, incorporating any
changes necessary to fix known bugs in prior
steppings.
storage A device or medium on or in which data
can be entered or held and retrieved at a later time.
Synonymous with memory.
storage area network (SAN) A network of
high-speed storage devices accessible by network
servers.
streaming In tape backup, a condition in which
data is transferred from the hard disk as quickly as
the tape drive can record the data so the drive does
not start and stop or waste tape.
string A sequence of characters.
subdirectory A directory listed in another direc-
tory. Subdirectories themselves exist as files.
subroutine A segment of a program that can be
executed by a single call. Also called program
module.
Super DLT (SDLT) An enhanced version of the
DLT tape standard that supports faster data transfer
and native/2:1 compressed capacities up to
300/600GB.
superscalar execution The capability of a
processor to execute more than one instruction at a
time.
surface mount Chip carriers and sockets
designed to mount to the surface of a PC board.
surge protector A device in the power line that
feeds the computer and provides protection against
voltage spikes and other transients.
suspend Refers to a level of power management
in which substantial power reduction is achieved
by the display or other components. The compo-
nents can have a longer recovery time from this
state than from the standby state.
SVGA (Super VGA) Refers to a video adapter or
monitor capable of 800×600 resolution.
SWEDAC (Swedish Board for Technical
Accreditation) Regulatory agency establishing
standards such as MPR1 and MPR2, which specify
maximum values for both alternating electric fields
and magnetic fields and provide monitor manufac-
turers with guidelines in creating low-emission
monitors.
switch Also called a switching hub, it’s a type of
hub that reads the destination address of each
packet and then forwards the packet to only the
correct port, minimizing traffic on other parts of
the network. Unlike a regular hub, which wastes
network bandwidth by copying packets to all ports,
a switch forwards packets to only their intended
recipients, immediately reducing network traffic
jams and improving overall efficiency for the entire
network. Many switches also support full-duplex
service, effectively doubling the speed of full-
duplex network cards attached to the switch. See
also hub.
SXGA (Super XGA) Refers to a video adapter or
monitor capable of 1280×1024 or greater resolu-
tion.
synchronous communication A form of com-
munication in which blocks of data are sent at
strictly timed intervals. Because the timing is uni-
form, no start or stop bits are required. Compare
this with asynchronous communication. Some
mainframes support only synchronous communica-
tion unless a synchronous adapter and appropriate
software have been installed. See also asynchronous
communication.
system crash A situation in which the computer
freezes up and refuses to proceed without reboot-
ing. Usually caused by faulty software, it’s unlike a
hard disk crash—no permanent physical damage
occurs.
Appendix A
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