S/360, S/390
Mainframe computers by IBM. The S/360 was introduced in the 1960s. The S/390 is a product of the 1990s.
SAG
SQL Access Group. A consortium of SQL providers.
SAM
(1) Sequentially Accessed Memory. Data that has to be accessed one chunk after another. This is analogous to a novel that you have to read from front to back. Most data is RAM instead of SAM but if the data is frequently accessed sequentially, such as in tape backups or certain databases, then SAM can have an advantage over RAM. See also ISAM and VSAM.

(2) .sam. SAMple. An extension indicating that the file is an example file. EG: The real hosts file is hosts, but a sample of the hosts file might be hosts.sam.
Samba
An open source implementation of the SMB file sharing protocol that provides file and print services to SMB/CIFS clients. Samba allows a non-Windows server (such as UNIX or Linux) to communicate with the same networking protocol as the Windows products.
sampling rate
The number of waveform samples taken per second (Hz). See sound.
SAN
Storage Area Network. Aka SDS (Shared Disk Subsystem). A sub network of shared storage devices on a network. A SAN is usually composed of RAID drives connected via 100 Mb/s fiber channel or 40 Mb/s SCSI. A SAN looks like a giant single drive to users. A SAN also frees up server power for applications since the server won't have to access its own hard drives as often but will instead merely point clients to the appropriate SAN.
sans serif
Typeface without little strokes added at the tips of characters, eg on Macs the typical sans serif fonts are Geneva, Chicago, and Monaco. The antonym is serif.
SAP
SystemAnalyse und Programmentwicklung. Aka Systems, Applications and Products in Data Processing. A company formed in 1972 by five former IBM employees in Mannheim, Germany. They make ERP (Enterprise Resource Planning) software, especially their R/3 system (an application suite) and their ABAP/4 Development Workbench. Their latest version is Web ready at mySAP.com.
satellite modem
A mini-dish antenna that sends and receives internet data via satellite at speeds up to 400 kb/s. Compare that to the typical analog modem of 33.6 kb/s.
saturation
The intensity of a color. EG: How green is that green? Full saturation of a hue, is that color without any tint (white) or tone (black) added. Desaturation eventually makes the hue disappear into gray.
scalability
The capability to increase the volume of work that a system can handle. This is in contrast with extensibility, which is the capability to extend the different kinds of functionality a system has.
Scalable Processor Architecture
See SPARC.
Scalable Vector Graphics
See SVG.
scale
See precision.
schema

(1) In SQL-92, a schema is the set of database objects (tables, procedures, etc.) owned by a single user and which form a single namespace. In MS SQL Server, a schema is implemented with database user ID, usually as the database owner.

(2) In database tools, schema is the catalog info describing the objects in a schema/database.

(3) In data warehousing, a schema is the structure of multidimensional objects, including dimensions and cubes.

scope
The range in which the contents of a variable are available. Variables declared within a function of a program are usually local. Variables declared outside of a function of a program are usually global.
scr
.scr. A Windows screen saver. It should be placed in the Windows directory.
scrape
To take output that was intended for one format and extract information from it to make it available for another format. EG: An application can take an HTML page and scrape information from it to make an RSS feed. See also screen scraper.
screen font
See bitmap font.
screening router
See SR.
screen saver
Applications that were originally designed to display different graphics so images wouldn't "burn" into the monitor. However most modern monitor cannot be burned anymore.

There are only two good reasons to use screen savers anymore. The first reason is because you think your screen saver is cool.

The second reason is because a screen saver can perform some level of security. A screen saver can be used to cover up what's on your monitor so no one else can see it. If you leave your computer for longer than you expected, than a screen saver with a password would disable others from seeing what you were working on; however, someone always reboot your machine, but close whatever applications you had open.
screen scraper
A program that takes character-based data from a mainframe and transforms it into GUI for users. Common screen scrapers include Mozart.com, FlashPt.com, and ScreenSurfer.com. See also scrape.
script
Denotes a programming language that does not have to be compiled but is usually used as a text file that can be interpreted and executed by the an interpreter for that language on that machine. This also implies that a scripting language does not need a developing environment and compiler. EG: JavaScript is a scripting language whose programs are saved as ASCII text and interpreted by JavaScript enabled browsers. Java on the other hand must be compiled with the JDK (Java Developers Kit, free from Sun) and it can create programs that can work alone.
scroll bars
The sliders and buttons on the sides of windows that help a user view a document that is larger than the size of the window.
SCSI
Small Computer System Interface. Pronounced scuzzy. A parallel interface protocol for connecting SCSI compliant peripherals such as scanners, printers, and hard drives. Devices may be daisy chained to a single SCSI port. SCSI was developed by Apple but is used by everyone. All Macs since the Mac Plus have as SCSI port. SCSI ports are usually backwards compatible with older SCSI peripherals. See also ATA (aka IDE), USB, FireWire, and connectors.
Name bits Max Cable (m) Max Speed (Mb/s) Max Devices
SCSI-1 8 6 5 8
SCSI-2
(aka SCSI)
16 6 5-10 8-16
Fast SCSI-2 16 3 10-20 8
Wide SCSI-2 32 3 20 16
Fast Wide SCSI-2 16 3 20 16
Ultra SCSI-3 8 1.5 20 8
Ultra SCSI-3 16 1.5 40 16
Ultra2 SCSI 8 12 40 8
Wide Ultra2 SCSI 16 12 80 16
Ultra3 SCSI
(aka Ultra 160/m)
16 12 160 16
SDH
Synchronous Digital Hierarchy. The standard for fiber optic data transmission by ITU. STS-1 is 51.84 Mb/s. STS-3 is 155.62 Mb/s. The ANSI equivalent of SDH is SONET.
SDLC
Synchronous Data Link Control. An SNA data transmission protocol.
SDK
Software Development Kit. A package for developers/programmers that allows them to make applications for a specific platform. An SDK
typically includes API's, programming tools, and documentation.
SDS
Shared Disk Subsystem. See SAN.
SEA
.sea. Self-Extracting Archive. A compressed file that can expand itself.
search engine
An application that searches for a topic that the user specifies. Yahoo! is common for the WWW, Archie is common for FTPs, Veronica and Jughead are common for Gophers. There are also search engines to search within a document depository, eg WAIS, Glimpse, HtGrep, SWISH, and Harvest.
SEC
Someone Else's Code. Borrowing someone's code for free or for a fee.
sector
The smallest subdivisions of tracks on a hard drive, usually measured in blocks. See also block and b.
sector sparing
A fault tolerance technique where the OS or the HW checks the integrity of the sector in a disk before writing to it. This only applies to SCSI drive or file systems which support it (such as Windows NTFS).
Secure Electronic Transaction
See SET.
Secure Sockets Layer
See SSL.
security
The set of preventative and reactive measures taken to minimize harm, whether intentional or not. Depending on your need for security, there are different measures that can be taken.
• Physical security
• Fault tolerance
• Secured transmissions
• Audits
• Access Control Lists
sed
Stream-oriented EDitor. A text editor common to UNIX systems.
A memory address space is logically divided into segments. To access a space, a program must specify the segment number and the offset within the argument. In contrast, a flat address space consists of a memory address that starts with zero and increments to the maximum address. Conversion between the two is called thunking.

Intel's 16-bit microprocessors (8086s to the80286s) and Win 3.X used 16-bit flat address spaces. Intel's 32-bit microprocessors (80386s to the Pentium III) and Win 95+ use 32 bit segmented memory address spaces. The Mac OS has always used flat addressing.
semiconductor
A material such as silicon or germanium that is neither a good conductor of electricity (like copper) nor a good insulator (like rubber). Semiconductors are "doped" with other elements to affect their properties such as an excess or a lack of electrons. Transistors, computer chips, integrated circuits, and other electronic parts are composed of semiconductors. Semiconductors allow smaller, faster, and more energy efficient components.
SEO
Search Engine Optimization. A variety of techniques for improving ranking of sites in search engines.
Sequentially Accessed Memory
See SAM.
Sequential Packet Exchange
See SPX.
Serial Line Internet Protocol/Point to Point Protocol
See SLIP/PPP.
serial port
A plug or interface in a computer system that transmits data on bit at a time, i.e. in series: one after another. This in contrast to a parallel port which transmits data several bits at a time, i.e. in parallel: side by side. Serial ports are often used devices such as keyboards, mice, tablets, and modems.

A common serial port is the RS-232 as set by the EIA/TIA. The RS-232 comes as either DB-25 (a 25 pin D-type connector) or DB-9 (a 9 pin D-type connector). The successors to the RS-232 are the RS-422 and RS-423, both of which are backwards compatible to the RS-232. The RS-422 supports multi-point connections. The RS-423 supports point-to-point connections. The RS-485 is like the RS-422 but can support more nodes per line.

Another common port is the PS/2 port by IBM used primarily for mice. It is a 6 pin DIN plug. Macs use the ADB/RS-422.

USB is a super serial port for both Macs and PCs that supports peripherals that have a higher data rate. See also port and connector.
serialization
Aka marshalling; deflation. The process of converting a data structure or object into a sequence of bits/bytes that can be stored as file, a memory buffer, or transmitted, for the purpose of deserializing (aka inflating; unmarshalling).
serif
Typeface with little strokes added at the tips of characters, eg on Macs the typical serif fonts are Times, Courier, New York, and Palatino. The antonym is sans serif.
servelet
A Java applet that runs on a (Web) server. This is analogous to a Java applet that runs within a (Web) client's browser. It is an alternative to using CGI scripts to access the server. Servelets are often faster since the servelet is persistent, as opposed to the CGI script which disappears once used.
server
(1) Software that serves up (shares) resources with users and clients.

(2) A beefed up computer that provides services on a network. It manages, stores, and shares resources and files that are accessed by users on the network, checking for authorizations and conflicts.

There are several types of servers including file, print, application, database, and web servers. Some servers are dedicated to one job, eg a dedicated file server, whereas other servers may do more than one job, eg a file and printer server.

A server will usually have a much larger hard drive than usual, a multitasking OS to execute many things at once, probably multiple network interface cards, and more ports. A server based network is more expensive than a peer-to-peer network when used for only a few computers but becomes cheaper per user as the network grows.

A "dumb server" merely serves up files or allows clients to print on a printer attached to the server. True client/server setups share the processing workload.
server based network
A network where a small number of dedicated servers provide service to a larger number of clients. The servers provide services and resources to the clients as well as manage and control access to the services and resources.

A server based network may be contrasted with a peer-to-peer network where each computer may be a server and/or a client.
Server Message Block
See SMB.
Server-Side Include
See SSI.
service bureau
A prepress company that provides high end desktop publishing services. Service bureaus especially have expensive image setters for outputting in the format needed (high resolution, film, etc.) prior to the final offset printing.
service oriented programming
See Web Services.
session
A connection between client and server that starts with a log on (usually utilizing a username and password) and ends with a log off.
SET
Secure Electronic Transaction. The credit card companies ideas for credit card security on the Internet. A largely over engineered, cumbersome, Dilbert-esque, useless, committee-designed, and largely ignored solution to a non-problem. For one, there are easier ways to get credit card numbers. Second, most consumers are also responsible for only up to $50 in charges if they promptly report that their numbers were stolen. Third, almost everyone uses something like CyberCash anyhow. To use a credit card on your website, there are three steps. 1. Collect the order info on a form or electronic shopping cart and have it point to the authorization service's web site. In the mean time make a new record in your database to start recording the transaction. 2. The authorization service displays a form to collect the customer's name, address, credit card number, etc. and processes the card. 3. The authorization service returns to your site with the results. Enter the returned info into the record you started in step one. SDRAM Synchronous Dynamic Random Access Memory. A PC RAM that is faster but more expensive than EDO RAM. It synchronizes memory speed with the processor bus. SGI Silicon Graphics Incorporated. A computer hardware and software company in Mountain View, California. SGA was founded in 1982 by Dr. James Clark and went public in 1986. It is especially known for high end special affects and animation, including those in motion pictures. SGI merged with MIPS Computer Systems in 1992, Alias Research and Wavefront Technologies in 1995, and Cray Research in 1996. SGML Standard Generalized Markup Language. ISO 8879, it is a much bigger document-processing system than HTML. SGML was created in 1974 by Charles F. Goldfarb. SGML defines descriptions of the structure and content of different types of electronic documents. Its primary focus is content, not appearance, so as to be small and cross-platform compatible. Unlike the fixed format of HTML, SGML can define its own tags or elements via the creation of a DTD (Document Type Definitions). EG: HTML is a DTD of SGML. XML is between SGML and HTML in that it is a subset of SGML specifically for the Web. SGRAM Synchronous Graphic Random Access Memory. A type of DRAM used in video cards. SGRAM is like SDRAM in that it synchronizes memory speed with the processor bus. It also uses other techniques like masked writes and block writes to increase its bandwidth. SGRAM is single-ported but since it can open 2 memory pages at a time, it can simulate dual-port memories like VRAM and WRAM. Shared Disk Subsystem SDS. See SAN. shared memory See dualport memory. shareware Aka trialware; demoware. Proprietary software that is distributed free on a trial basis, hence half-gratis. Shareware may be a limited version of the full version or has some annoying feature. Crippleware is a variation of shareware that offers a very poor version of the full version. See also freeware. shell Unix provides shells that allow a user to interface with the "kernel" (lower level of the operating system). Unix shells are traditionally CLIs (Command Line Interface) where users can type to interface, but can be GUI (Graphical User Interface). Here are some of the shells available for Unix, in rough historical order and complete with the original bad puns: • First • sh. Thompson shell. The first shell. By Ken Thompson at Bell Labs in 1971 for Unix 1. • Second Generation • sh. Bourne shell. /bin/sh. By Steve Bourne at Bell Labs in 1978 for Unix 7. Bourne shell and its derivatives usually have a CLI prompt ending with $.
• csh. C shell. /bin/csh. By Bill Joy (creator of BSD UNIX) in 1979 for BSD. C shell and its derivatives usually have a CLI prompt ending with %.
• Third Generation
• Usually Bourne shell improvements
• ksh. Korn shell. /bin/ksh or /usr/bin/ksh. By Dave Korn in the early 1980s.
• bash. Bourne-Again shell. /bin/bash, /usr/bin/bash, or /usr/local/bin/bash. By Brian Fox in 1987. Probably the most popular shell as of 2005. bash has even been ported to Windows by Cygwin.com. GNU.org/software/bash/
• Usually C shell improvements
• tcsh. TENEX C shell. /bin/tcsh, /usr/bin/tcsh, or /usr/local/bin/tcsh. By Ken Greer in the 1970s.
• Others
• ash. Almquist shell.
• scsh. Scheme shell.
• sh. PWB shell.
• zsh. Z shell.

In one sense X Windows System of Unix, the Window OS of Microsoft, and the Mac OS, are all GUI "shells". Apple/Mac uses AppleScript, but MacOS X uses bash. Microsoft Windows users will compare the Unix shell to DOS or the Windows CLI opened up via command.com or cmd.exe. Windows shell scripts are wsh. The DOS prompt usually ends with > .
shell account
A connection to an ISP where your computer is essentially a dumb terminal since all the computing work is done on the ISP's server. Some accounts are both shell and SLIP/PPP where the computing work is done on your computer.
Shielded Twisted Pair
See STP.
Shift State
Shift State is knowledge of the which keys were pressed before the current keys, and is usually concerned with the combinations of SHIFT, CTRL, ALT, ALTGR (the right hand side ALT), CAPS LOCK, etc., either simultaneously or in sequences. See also dead keys and Character Set Shortcuts.
shortcut keys
A combination of keys that the user presses to access commands without opening pull down menus. EG: Pressing ctrl-S will usually execute the Save command in the Windows OS; similarly pressing command-S will usually execute the Save command in the Macintosh OS. In contrast to shortcut keys, access keys access commands and open pull down menus. See also Microsoft Shortcuts and Character Set Shortcuts.
.shtml
See SSI.
S-HTTP
An extension developed by EIT/Verifone in 1995. It supports secure data transmission of individual messages. S-HTTP can work in conjunction with the more prevalent SSL, which supports secure data connections.
sigil
In programming, a sigil is a symbol attached to a variable to indicate that the variable is a variable and sometimes also the datatype, class, or general category. BASIC, PERL, and PHP are famous for using a $ sigil for strings. EG: PERL has $scalar = 'Fred', @list = (11,13,17), and %myHash = (a => 'x', b = 'y').
Signaling System 7
See SS7.
signal-to-noise ratio
The ratio of useful data to non-useful data, eg the quantity of junk mail and Spam on a newsgroup versus the quantity of good material.
signature
The signature of a type (function, subroutine, or method) defines its name, and the input and output parameters.
Silicon Graphics Incorporated
See SGI.
SIMM
Single In-Line Memory Module. A circuit board that holds groups of RAM chips. SIMMs plug into sockets on the computer motherboard. It has either 30 or 72 pins and is roughly 3 or 4 inches long respectively. The bus for a SIMM is 32 bytes wide.
Simple Mail Transfer Protocol
See SMTP.
Single In-Line Memory Module
See SIMM.
Simple Network Management Protocols
See SNMP.
Simple Object Access Protocol
See SOAP.
Single Page Application
See SPA.
singleton
(1) In object oriented programming, this is a design pattern that restricts the instantiation of a class to only one object. That is only one object of that class will ever be needed. A singleton is in effect a global or system wide object.

(2) In markup languages like XML or XHTML, a singleton is an empty or self enclosing tag. EG: <RegularTag>hi</RegularTag> versus <SingletonTag />.

(3) In math, a singleton is a set with exactly one element. EGs: {3} or {{1,2,3}}.
sit
.sit. A file that has been compressed via the Mac program Stuffit.
SKU
Stock Keeping Unit. An ID associated with a product for inventory purposes.
SLIP
Serial Line Internet Protocol. Protocol for connecting computers via phone. It allows the user a variety of applications to access the server as opposed to shell or terminal access which usually can only be accessed by specific programs. Usually PPP is preferred over SLIP.
Slot 1
See form factor.
Small Computer System Interface
See SCSI.
Smartdrive
A 16 bit disk caching system used by later version of DOS and Windows 3.X. Smartdrive monitors cache usage and give the user the option to change the cache size. See also VCACHE.
SMB
Server Message Block. A message format utilized by DOS and Windows to share files, directories, and devices. Many network products use SMB, including NetBIOS, LAN Manager, Windows for Workgroups, and Windows NT. Some products even use SMB to share between different operating systems, EG Samba uses SMB to share between UNIX and Windows.
SMDS
Switched Multimegabit Data Services. A telecommunications development from 1995. It is an alternative to using dedicated private lines for joining LANs to form a WAN. It is a high-speed switched data communications service.
smellified
XML-ified. Data that has been converted into an XML data source. As far as I know, I invented this term ca. 2003-06-21!
S/MIME
Secure Multipurpose Internet Mail Extensions. See MIME.
SMP
(1) Symmetric MultiProcessing. See multiprocessing.

(2) Short for SNMP.
SMTP
Simple Mail Transfer Protocol. A protocol developed in 1982 that is used to transfer internet e-mail. SMTP described protocol for the formatting, encoding, and exchanging of ASCII messages across different types of networks, machines, and platforms.

SMTP communicates with POP mail servers. SMTP limits messages to ASCII characters with no more than 1000 characters per line. See also MIME.
smurf
To disable a network by sending swarms of PINGs that have the victims addressed spoofed as the originator, thus swamping the system with thousands of fake little requests and messages per second. It is not quite hacking because no information is stolen, but it is still a security issue.
SNA
System Networking Architecture. A protocol for WANs developed by IBM in the 1970s. It is especially prevalent in the IBM mainframe WAN world, much as TCP/IP is prevalent in the Internet WAN world. SNA is still used by systems that use mainframes such as banks and airlines.

SNA has a seven layer structure like the OSI Reference Model. The layers are: Physical, Data Link, Path Control, Transmission Control, Data Flow Control, Presentation Services, and Transaction Services.
snert
A rude or malicious disruptor of IRC chat rooms or message boards.
snd
.snd. A sound file format for Macs.
SNMP
Simple Network Management Protocols. Aka SMP (Simple Management Protocol). A popular set of standards for network management first developed in the 1980s. In this scheme nearly each device on the network has a small program, called an agent, which gathers data on the status of the device. The agent then sends the data in MIB (Management Information Base) format to a central management console program, which polls the agents regularly and takes appropriate actions such as disconnecting a node or setting of an alarm for a human operator. See also RMON.
SOAP
Simple Object Access Protocol. SOAP encodes info (as XML) for Web Service transport via various Internet protocols such as SMTP, MIME, and HTTP. See also Web Services.
sockets
A socket itself identifies the computer and the process, usually with the IP number and a port number. Sockets is a name for how some client server programs communicate.
Socket 7, 8
See form factor.
soft page fault
See page fault.
software
The programs that detail the operations to a computer. This includes operating system (OS) software, user interface software to facilitate communication with the OS, and any of the various user programs (applications) such as word processor and utilities. The hardware is the first level of a computer, the software is the second level.
software development kit
See SDK.
Software Publishers Association
See SPA.
SOM
System Object Model. IBM's architecture for component software. It is CORBA compliant. It is a counter to Microsoft's COM. The distributed object version of SOM is DSOM (Distributed SOM). DSOM is a counter to Microsoft's DCOM and Sun's RMI.
SONET
Synchronous Optical NETwork. A standard for fiber optic transmission. It was established by Bellcore in the 1980s and is now supported by ANSI. (The international equivalent is ITU's SDH). SONET works with the Physical Layer of the OSI Reference Model and establishes the OC rates (51.85 Mb/s to 2.488 Gb/s) for fiber optics.
SOP
Service Oriented Programming. See Web Services.
SourceSafe
Microsoft Visual SourceSafe. An application that coordinates a team of developers working on an application.
SPA
(1)Software Publishers Association. A group of PC industry companies and organizations. They established the MPC standards.

(2)Single Page Application. A web application that runs largely on one page. It modifies its data, content, and appearance by manipulating its DOM locally. For true persistence though, a SPA should eventually have some way of saving some of the data either locally or to the server —usually via a "Save" button.
Spam
(1) Unnecessary or unwanted email, i.e., junk mail.

(2) Excessive mulit-posting and excessive cross-postings at news groups and message boards. Some extend the definition to off-topic postings.
spamdexing
The practice of entering keywords multiple times in a web page so that it will rise to the top of a results list of a search since some search engines rate their results by the number of occurrences of the search keyword.
SPARC
Scalable Processor ARChitecture. RISC based microprocessors by SPARC International. SPARC machines run Sun's Solaris OS.
Speech Recognition Technology
See SRT.
splash screen
The startup or introductory visual when a program starts.
spoof
To fool, especially to fool hardware and software in a network in order to test them. A typical scenario is to send a message so that it seems to have originated from a specific IP address.
spool
To save a file until it can be processed. This often refers to files waiting on queue to be printed.
sprite
A 2D image or animation that is typically integrated into a larger scene. This is in contrast with 3D modeling (meshing).
SPX
spyware
Small programs that record or transmit user's activity (usually in secret). Spyware invades privacy and can slow down a computer.
SQL
Structured Query Language. Pronounced "sequel". SQL is a cross platform language used to select, update, insert, or delete data in relational databases. See also my section on Databases and SQL.
SR
Screening Router. A router used to filter packets for a network. See also firewall and my article on Security.
SRAM
Static Random Access Memory. A volatile RAM chip that does not have to be refreshed as often as DRAM which makes it faster but more expensive.
SRT
Speech Recognition Technology. Technology and software that translates speech into text.
SS7
Signaling System 7. A telecommunications protocol set by the ITU that can help PSTN congestion with digital wireless networks. SS7 enables hi speed packet switching and out-of-band signaling with SS7 nodes. SS7 nodes are signaling points consisting of SSPs (Service Switching Points), SCPs (Service Control Points), and STPs (Signal Transfer Points). Out-of-band signaling utilizes a digital channel that is separate from the data/conversation channel.
SSI
Server-Side Include. An SSI is an element that can be included in multiple web pages. SSI elements must be placed in a directory with Script or Execute permissions. An SSI element can even be a file with active code such as a shell command, a CGI program, ASP code, or an ISAPI DLL.

The pages that use the SSI elements usually have a file extension of either .shtml, .shtm, or .stm, but are otherwise just like .htm files. A web server knows where SSI elements are placed at specific points within a file by SSI directive code. It should be noted that #include SSI directives can be used in .asp pages. Here are examples of SSI directives:
<!-- a path relative to the current document. / -->
<!-- #include file="../common/readme.txt" / -->
<!-- a path relative to the base document, usu. the home page. / -->
<!-- #include virtual="\common\readme.txt" / -->
<!-- Runs an app at a given URL. / -->
<!-- #exec
cgi="http://www.my.com/scripts/guestbook.exe!FirstName+LastName"
-->
You do not need SSI if you are pointing to a script file. You could use a <script> tag similar to this example:
<script type="text/vbscript" src="includes/myScript.vbs">
SSL
Secure Sockets Layer. A protocol that increases the security of transmitting confidential data such as credit card numbers over a network. SSL grants client/server applications a secure session in the Session layer of the OSI Reference Model. By providing data encryption, server authentication, message integrity checking, and client authentication, it can help prevent eavesdropping, tampering, and forgery. Web pages that require an SSL connection start with https: instead of the usual http:.

SSL can work in conjunction with S-HTTP. While SSL creates a secure connection, S-HTTP creates secure individual messages.
stack
(1) Processing memory that is very fast but of which there is a limited amount. Variables that use the stack have their actual data stored in that memory space and thus must be of a known data type and size at compile time. See also heap.

(2) Aka LIFO (last-in, first-out). A data structure where items are removed in the reverse order that they were added, i.e. the later additions are removed sooner. Think of a stack of dishes in a spring-loaded bin. Items are added or "pushed" on the stack (EG: 1, 2 becomes 1, 2, 3), and then removed or "popped" from the stack (EG: 1, 2, 3 becomes 1, 2). See also queue and JavaScript Array.. See also RPN.
stack operation
See RPN.
stand alone
A computer, device, or application that is not connected to a network.
Standard Generalized Markup Language
See SGML.
state machine
A device that is supposed to be in a known state at all times. EG: Most machines are either on or off. EG: Software that is a state-machine may be in states such as pause, edit, idle, or add.
statement
A complete sentence in a program. A statement is collection of keywords, identifiers, properties, functions, operators, and symbols that the particular programming language recognizes. A statement can be a single word (EG: beep), but statements are usually one line long or longer. Statements are sometimes collected together (usually with {curly brackets}) into blocks that can act as a single statement.
static
(1) In object oriented programming, a static member, usually a method or variable, is one that is available at the class level, i.e. an object of the class does not have to be instantiated, and the static member can be used right away. Static variables are similar to constants. EG: Math.random() typically returns a random number between 0 and 1.
(2) Static typing is when a programming language performs type checking at compile-time instead of run-time, the latter of which is called dynamic typing.
s. th.
SomeTHing.
Storage Area Network
See SAN.
storage memory
Non-volatile memory that does not lose its contents when the power is turned off. This is analogous to data in books and in notes on file. Examples include floppy disks, hard drives, tape backups, CMOS, and CD-ROMs. See also processing memory.
stored procedure
A soupped up query that is stored precompiled at the database. A stored procedure can be run with a simple call from an application but it can enable flow control statements, user declared variables, and misc. non-SQL programming.
STP
Shielded Twisted Pair. It is pairs of insulated, color coded wire and typically uses an IBM data connector. Each pair is twisted (to cancel out electrical noise) and each pair is also twisted a different number of twists per inch. In addition, each pair is foil wrapped, then all the pairs are then foil wrapped together, then that unit is sheathed in braided copper shielding and an outer jacket. Of the four common media, STP is very fast, physically large, expensive, and has a fairly short cable length. See also media and 10BASE-X.
stream
To have audio or video play as it loads.
Stock Keeping Unit
See SKU.
structured programming language
A language that avoids commands, such as BASIC's use of the GO TO command, which creates branch points in the logical flow of a program. A program with too many branch point can be difficult to trace and debug. COBOL is an example of a structured programming language.
Structured Query Language
See SQL.
style sheets
Aka templates. In DeskTop Publishing, a style sheet is a file or form that defines the generic layout of a document, i.e. the page size, margins, fonts, and colors. A style sheet can be used to start many instances of that type of document.
subnet
A 32 bit combination designating the start of a subnet. See also IP.
A 32 bit combination used to describe which portion of an IP address belongs to the network and subnet, and which part belongs to the host/interface. EG: In a Class C network with 6 subnets, the subnet mask masks the first three octets, and two of the eight bits in the last octet:
11111111.11111111.11111111.11100000 (subnet mask in binary)
255. 255. 255. 224 (subnet mask in decimal)
Subversion
See svn.
superparamagnetic effect
The physical limit to areal density: at such densities magnetic particles can't help but interfere with each other. The limit is roughly 40 Gb/in^2.
Super Video Graphics Array
See SVGA.
SVC
Switched Virtual Circuit. See virtual circuit.
SVG
Scalable Vector Graphics. SVG is an open W3C recommendation for 2D graphics (either static or dynamic) driven by XML and is fully scriptable. It's been up and coming for a while —competing against Macromedia's Flash (.swf) and Microsofts VML (Vector Markup Language)— but I think it will finally gain momentum in certain areas. SVG will be very good for data-driven stuff, while Flash will will probably reign for design-driven stuff.
svn
Subversion. A popular open source product for reversion control. See also reversion control.
SVGA
Super Video Graphics Array. The next step up from VGA. It has a resolution of up to 1024 x 768 pixels. See video standards.
SVR4
See UNIX.
SWISH
Simple Web Indexing System for Humans. A search engine used to index depositories of files and search through them.
Switched Multimegabit Data Services
See SMDS.
Switched Virtual Circuit
SVC. See virtual circuit.
symmetric key encryption
Aka secret key encryption. An encryption system where the sender and receiver use the same key to encrypt and decrypt the message. This is in contrast to the more complicated public key encryption method. The sender and receiver must somehow agree upon the key in a secure way before the message is transmitted. DES is a popular symmetric key encryption system.
See SDLC.
Synchronous Digital Hierarchy
See SDH.
Synchronous Dynamic Random Access Memory
See SDRAM.
Synchronous Optical Network
See SONET.
syntax
The rules that describe how to form and construct various elements of a language. It is the anatomy of statements.
syntax error
A runtime error due to a violation of syntax by the program.
System/360, System/390
See S/360, S/390.
system design and analysis
Studying a real world system, such as tasks performed by a business, and implementing it with a computer system.

Analysis of a real world system should yield the following:
• A statement of the system's purpose and scope.
• Models of the process flow, often utilizing a DFD (Data Flow Diagram).
• Models of the database, often utilizing an ERD (Entity Relationship Diagram)
• Models of the user screen interfaces.
• Models of the user reports printed out.

System design and analysis involves varying quantities of people. An individual or a small SWAT-like team can be used, especially in RAD (Rapid Application Development). For long term application, the following people are typically involved in system design and analysis:
• A recorder who uses CASE, DFDs, ERDs, etc.
• End users.
• An executive or manager who can okay budgeting.
• Developers and programmers.
• Any other technical specialists.

Always implement quality control and documentation throughout design and analysis. A computer system typically has the following life cycle:
1. Feasibility Study.
2. Analysis.
3. Design.
4. Implementation.
5. Acceptance Testing.
6. Production.
7. Maintenance.
8. Obsolescence.
system integrators
People or organizations that take pre-made software and hardware, customize it, and add additional stuff, for the purpose of providing complete systems to other companies. Here are some big name systems integrators: Accenture (formerly Andersen Consulting), Compaq, Computer Sciences Corporation, Deloite Consulting, EDS, Ernst & Young, HP, IBM Global Services, and Price Waterhouse.
System Networking Architecture
See SNA.
System Object Model
See SOM.
system resources
Channels of communication between components of a computer system, eg IRQs and DMA. System resources also handle the details of a GUI, such as windows, menus, dialog boxes, icons, scroll bars, check boxes, buttons, etc. A computer will have a finite number of system resources.
system unit
The hardware that processes computer data. It consists of boards or cards enclosed in a case and supplied with power. The boards are usually the CPU, the RAM, and the I/O to connect the system unit to the backend and front end. The cards within the system unit are connected via bus.
system tray
See systray.
systray
SYStem TRAY. In the Windows OS, this is the little box on Task Bar opposite of the Start button. It usually displays the time but can also display miscellaneous programs running or waiting in the background such as anti-virus programs, web servers, and volume control panels.

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