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Safe mode The mode in which Windows 95 is loaded with minimum configuration and drivers in order to allow the correction of system errors. To enter Safe mode, press F5 or F8 when "Starting Windows 95" is displayed.

SAM (Security accounts manager) A portion of the Windows NT registry that manages the account database that contains accounts, policies, and other pertinent information about the domain.

Sample size Refers to samples taken when converting a signal from analog to digital. Sample size is a measure of the amount of storage allocated to storing a single measurement of a single sample. The larger the sample size, the more accurate the value and the larger the file sizes needed to store the data.

Sampling Part of the process of converting sound or video from analog to digital format, whereby a sound wave or image is measured at uniform time intervals and saved as a seris of smaller representative blocks. See Sampling rate.

Sampling rate The rate or samples taken of an analog signal over a period of time, usually expressed as samples per second or Hertz. For example, 44,100 Hz is the sampling rate used for 16-bit stereo.

SCAM (SCSI configuration automatically) A method in which SCSI devices and the host adapter are Plug-and-Play-compliant, and the user does not need to manually set the ID on the device.

Scanning mirror A component of a laser printer. An octagonal mirror that can be directed in a sweeping motion to cover the entire length of a laser printer drum.

SCSI (small computer system interface) A system-level interface designed for general purpose applications that allows up to seven devices to be connected to a single host adapter. It uses an 8-bit parallel connection that produces a maximum transfer rate of 5Mb per second. The term is pronounced "scuzzy."

SCSI bus A faster bus standard used for peripheral devices tied together in a daisy chain.

SCSI bus adapter chip The chip mounted on the logic board of a hard that allows the drive to be a part of a SCSI bus system.

SCSI ID See Logical unit number.

SCSI-1 The oldest SCSI bus standard, established in 1986, which requires an 8-bit parallel bus with optional parity checking.

SCSI-2 An improved version of SCSI-1 with several new features and options added. Although compatible, the additional features found in SCSI-2 will be ignored by SCSI-1 devices.

SDRAM (Synchronous DRAM) A DRAM technology that uses a clock to synchronize signal input and output on a memory chip. The clock is coordinated with the CPU clock so the timing of the memory chips and the timing of the CPU are "in synch." Synchronous DRAM saves time in executing commands and transmitting data, thereby increasing the overall performance of the computer. SDRAM allows the CPU to access memory approximately 25 percent faster than EDO memory.

Sector The basic storage unit on a hard disk. On most modern hard disks, sectors are 512 bytes each, four sectors make up a cluster, and there are 17 to 34 sectors in a track although newer drives may have a different number of sectors.

Segmentation To spilt a large Ethernet into smaller segments that are connected to each other by bridges or routers. This is done to prevent congestion as the number of nodes increases.

Sequential access A method of data access used by tape drives whereby data is written or read sequentially from the beginning to the end of the tape or until the desired data is found.

Serial mouse A mouse that uses a serial port and has a female DB-9 plug.

Serial port The "male" connector (usually DB-9 or DB-25) on the back of your computer. It sends out data one bit at a time. It is used by mice, modems and, in years past, for daisy-wheel and other printers. In DOS serial ports are called COM1 or COM2. See also COM.

Session layer The OSI layer that makes and manages a connection between two nodes of the network.

SGRAM (Synchronous Graphics RAM) Memory designed specifically for the video card processing that can synchronize itself with the CPU bus clock.

Shadow mask Inside the color monitor just behind the screen, it is drilled with small holes, each of which corresponds to a triad. The shadow mask helps guide the electron beams so that each beam hits only one phosphor dot in the triad.

Shadow RAM, Shadowing ROM ROM to speed up the system operation, because of the faster access speed of RAM.

Shell A piece of software providing direct communication between the user and the operating system. The main inner part of the system, called the kernel, is enclosed by the shell program, as in a nut.

Signal-regenerating repeater A repeater that "reads" the signal on the network and then creates an exact duplicate of the signal, thus amplifying the signal without also amplifying unwanted noise that is mixed with the signal.

SIMD (Single instruction multiple data) An MMX process that allows the CPU to execute a single instruction simultaneously on multiple pieces of data rather than by repetitive looping.

SIMM (Single In-line Memory Module) A printed circuit board with gold or tin/lead contacts and memory devices. A SIMM plugs into a computer’s memory expansion socket. SIMMs offers two main advantages: ease of installation and minimal consumption of horizontal surface area. A vertically mounted SIMM requires only a fraction of the space required by horizontally mounted DRAM. A SIMM may have as few as 30 or as many as 200 pins. On a SIMM, the metal leads on either side of the board are electrically "tied together."

Single voltage CPU A CPU that requires one voltage for both internal and I/O operations.

Single-ended SCSI device A SCSI device that uses half the number of wires in the cable that a differential device uses, and is limited in the cable length.

Sleep mode A mode used in many "green" computers that allows them to be programmed through CMOS to suspend the monitor or even the drive if the keyboard and/ or CPU have been inactive for a set number of minutes.

SLIP (Serial Line Internet Protocol) An early version of line protocol designed for home users connecting to the internet. SLIP lacks reliable error checking and has mostly been replaced by PPP.

Slot A socket on the systemboard into which adapter boards or interface cards can be installed.

Slot mask Also known as an aperture grille, it serves the same function as the shadow mask on a monitor.

SMARTDrive A hard drive cache program that comes with Windows 3.x and DOS that can be executed as a TSR from the AUTOEXEC.BAT file.

SMTP (Simple Mail Transfer Protocol) A common protocol used to send e-mail across a network.

Socket A virtual connection from one computer to another such as that between a client and a server. Higher-level protocols such as HTTP use a socket to pass data between two computers. A socket is assigned a number for the current session, which is used by the high-level protocol.

Software Programming tools such as languages, assemblers, and compilers; control programs such as operating systems; or application programs such as electronic spreadsheets and word processors. Software instructs the computer to perform tasks. See also Application software.

Software cache A disk cache that is stored on the hard drive as software and uses RAM to hold the cache. It is usually loaded into memory as a TSR.

Software copyrights Copyright is a legal concept (covered by the Federal Copyright Act of 1976) that encompasses the protection of the rights of an originator of a creative work, which can include software. With the exception of archival backups, copyrighted programs are illegal to copy without specific authorization from the copyright holder.

Software piracy Making unauthorized copies of original copyrighted software.

SOHO (Small Office/Home Office) The fastest growing market for computer hardware and software. So-called SOHO products are specifically designed to meet the needs of professionals who work at home or in small offices.

SO DIMM (Small Outline Dual In-line Memory Module) An enhanced version of a standard DIMM. The small outline DIMM is about half the length of a typical 72-pin SIMM.

Spindle One part of a hard disk, around which the platters rotate.

Spreadsheet An application commonly used for budgets, forecasting and other finance-related tasks. Data and formulas to calculate those data are entered into ledger-like forms (spreadsheets or worksheets) for analysis, tracking, planning, and evaluation of impacts on economic strategy.

SQL (Structured Query Language) A query language developed by IBM that relies on simple English-language statements to perform database queries. Almost universally supported in one form or another by relational databases on platforms of all types, SQL allows databases from different manufacturers and on different types of computers to be queried using a standard syntax. See also ODBC.

SRAM (Static RAM.) RAM chips that retain information without the need for refreshing as long as the power is on. They are more expensive than traditional DRAM.

Stack A place in memory where information, such as addresses of pending tasks for the CPU, is kept.

Standby time The time before a "green" system will reduce 92 percent of its activity.

Standby UPS A UPS that quickly switches from an AC power source to a battery-powered source during a brownout or outage.

Standoffs Small plastic spacers placed on the bottom of the main systemboard, to raise it off the chassis, so that its components will not short out on the metal case.

Star network architecture A network design in which nodes are connected at a centralized location.

Star bit A bit that is used to signal the approach of data.

Static electricity See Electrostatic discharge.

Static IP addresses IP addresses permanently assigned to a workstation. In Windows 95, this can be done under Dial-Up Networking, Server Type, TCP/IP settings. Specify an IP address.

Static routing When routing tables do not automatically change and must be manually edited. Windows NT and Windows 95 support only static routing.

Stealth virus A virus that actively conceals itself by temporarily removing itself from an infected file that is about to be examined, and then hiding a copy of itself elsewhere on the drive.

Stop bit A bit that is used to signal the end of a block of data.

Subnet mask Defines which portion of an IP address identifies the network, and which portion identifies the host. A 1 in the mask indicates that the bit is part of the network address, and a 0 indicates that the bit is part of the host address. For example, the subnet mask 255.255.192.0, in binary, is 11111111.11111111.11000000.00000000.

Therefore, the network address is the first two octets and the first two bits of the third octet. The rest of the IP address refers to the host.

Subnetworks or subnets Divisions of a large network, consisting of smaller separate networks (to prevent congestion). Each subnetwork is assigned a logical network IP name.

Substrate The base layer of a chip, printed circuit board or multichip module (MCM) onto which semiconductor devices are fabricated. Silicon is the most widely used substrate for chips. Fibreglass is mostly used for printed circuit boards, and ceramic is used for MCMs.

Subtree One of five main keys that make up the Windows NT registry. Examples are

HKEY_CURRENT_USER and

HKEY_LOCAL_MACHINE.

Surge suppressor A device or power strip designed to protect electronic equipment from power surges and spikes.

Suspend time The time before a "green" system will reduce 99 percent of its activity. After this time, the system needs a warm-up time so that the CPU, monitor, and hard drive can reach full activity.

Synchronous Communication Fixed-rate serial communication, eliminating the need for transmitting inefficient start-stop information. PC-to-mainframe communication may be synchronous; most PC-to-PC communication is asynchronous. Most laptop modems are asynchronous only. If you're not sure whether you need a synchronous-asynchronous modem, you probably don't.

Synchronous Refers to events that are synchronised, or co-ordinated, in time. Communication within a computer is usually synchronous and is governed by the microprocessor clock. Signals along the bus, for example, can occur only at specific points in the clock cycle.

System-level interface A connection between the hard disk and its host system that puts control and data-separation functions on the drive itself (and not on the external controller). SCSI and IDE are system-level interfaces.

Swapping A method of freeing some memory by moving a "page" of data temporarily to a swap file on the hard drive; it can later be copied from disk back into memory.

Synchronous DRAM See SDRAM.

Synchronous SRAM SRAM that is faster and more expensive than asynchronous SRAM. It requires a clock signal to validate its control signals, enabling the cache to run in step with the CPU.

System BIOS See BIOS.

System partition The active partition of the hard drive containing the boot record and the specific files required to load Windows NT.

System variable A variable that has been given a name and a value; it becomes available to the operating system, Windows, and applications software programs.

Systemboard The main board in the computer, also called the motherboard. The CPU, ROM chips,SIMMs or DIMMs etc…, and interface cards are plugged into the systemboard.

Systemboard mouse A mouse that plugs in to a round mouse port on the systemboard.