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Friday, February 25, 2011

Computer Terms P-T


• PPP:
Stands for Point To Point Protocol. It’s a software application that allows an attachment to a server.
• Packet:
A unit of data formatted to transmit through a network. A packet is sent from a source to a destination.
• Parallel Port: A parallel interface for connecting an external device such as a printer. Most personal computers have both a parallel port and at least one serial port. On PCs, the parallel port uses a 25-pin connector (type DB-25) and is used to connect printers, computers and other devices that need relatively high bandwidth. It is often called a Centronics interface after the company that designed the original standard for parallel communication between a computer and printer. (The modern parallel interface is based on a design by Epson.)
A newer type of parallel port, which supports the same connectors as the Centronics interface, is the EPP (Enhanced Parallel Port) or ECP (Extended Capabilities Port). Both of these parallel ports support bi-directional communication and transfer rates ten times as fast as the Centronics port.
Macintoshes have a SCSI port, which is parallel, but more flexible.
• Parity: In data communications, this is an data error detection scheme. It deals with a fact that all numbers have a parity (odd or even, eg: 1 or 0).
• Partition: A portion of a hard disk that functions as a separate unit. A single hard disk can be divided into several partitions, each of which functions as a separate drive and has its own volume name (such as D:, E:, F:, and so on). The purpose is to make the drive more efficient, as the computer can search smaller sections for a specific file rather than the entire drive. The verb to partition refers to the process of dividing the hard drive into partitions.
• Passive Matrix: An older form of LCD (liquid crystal display) technology that processes pixels using row-and-column formatting. This type of formatting produces slower responce times and lower contrast ratios when compared to Active Matrix LCD.
• Patch Panel: In networking a patch panel connects all networked computers to the incoming and outgoing lines of a LAN (Local Area Network) or any other electronic communications system.
• Path: A path can be described as a file’s address on your file system, describing where the file lives: An absolute path gives the complete path, starting at the root directory, or the very top of the file system; A relative path looks for a file from the directory you are currently in down.
• PCI:
Acronym for Peripheral Component Interconnect, a local bus standard developed by Intel Corporation. Most modern PCs include a PCI bus in addition to a more general ISA expansion bus. Many analysts, however, believe that PCI will eventually supplant ISA entirely. PCI is also used on newer versions of the Macintosh computer.
PCI is a 64-bit bus, though it is usually implemented as a 32-bit bus. It can run at clock speeds of 33 or 66 MHz. At 32 bits and 33 MHz, it yields a throughput rate of 133 MBps.
Although it was developed by Intel, PCI is not tied to any particular family of microprocessors.
• PDF: Stands for Portable Document Format. A technology developed by Adobe and was designed to capture all of the elements of a printed document and place it in a singe image file. This PDF file can be navigated, printed or attached to an email for sharing. In order to be able to view a PDF file on your computer, you will need to download and install the free Acrobat Reader. Once installed, anytime a PDF file is clicked, the image file will automatically be viewed.
• Peer to Peer: A type of network in which each workstation has equivalent capabilities and responsibilities. This differs from client/server architectures, in which some computers are dedicated to serving the others. Peer-to-peer networks are generally simpler and less expensive, but they usually do not offer the same performance under heavy loads.
• Pen Drive: A small keyring-sized device that can be used to easily transfer files between USB-compatible systems. Available in a range of capacities (and in some cases, with an MP3 player built-in). Plug it in to any USB port and it will be automatically detected by the Operating System.
• Peripheral: Any external device attached to a computer. Examples of peripherals include printers, disk drives, display monitors, keyboards, and mice.
• PGA: Short for Pin Grid Array, a type of chip package in which the connecting pins are located on the bottom in concentric squares. PGA chips are particularly good for chips that have many pins, such as modern microprocessors. Compare with DIP and SIP. Short for Professional Graphics Adapter, a video standard developed by IBM that supports 640×480 resolution.
• Phishing: Short for Password Harvesting Fishing. It is the luring of sensitive information, such as passwords and other personal information, from a victim by masquerading as someone trustworthy with a real need for such information.
Popular targets are users of online banking services, and auction sites such as eBay. Phishers usually work by sending out spam e-mail to large numbers of potential victims. Typically the email will appear to come from a trustworthy company and contain a subject and message intended to alarm the recipient into taking action.
A common approach is to tell the recipient that their account has been de-activated due to a problem and inform them that they must take action to re-activate their account. The user is provided with a convenient link in the same email that takes the email recipient to a fake web page appearing to be that of a trustworthy company. Once at that page, the user enters her personal information which is then captured by the fraudster.
• PHP: (Hypertext Preprocessor) is a server-side, HTML-embedded scripting language used to create dynamic Web pages. In an HTML document, PHP script (similar syntax to that of Perl or C) is enclosed within special PHP tags. Because PHP is embedded within tags, the author can jump between HTML and PHP (similar to ASP and Cold Fusion) instead of having to rely on heavy amounts of code to output HTML. Because PHP is executed on the server, the client cannot view the PHP code. PHP can perform any task any CGI program can, but its strength lies in its compatibility with many types of databases. Also, PHP can talk across networks using IMAP, SNMP, NNTP, POP3 or HTTP.
• PICT:
Pronounced “Pick,t.” It is another image format.
• PING:
Packet Internet or Inter-Network Groper; a utility used to determine whether a particular computer is currently
connected to the Internet. It works by sending a packet to the specified IP address and waiting for a reply. The computer acronym “PING” was contrived to match the submariners’ term for the sound of a returned sonar pulse.
• Pinout:
A diagram or table that describes the purpose of each pin in a chip or connector, or each wire in a cable.
• PIO: (Programmed Input/Output) A method of data transfer in which the host microprocessor transfers data to and from memory via the computer’s I/O ports. PIO enables very fast data transfer rates, especially in single-tasking operating systems like DOS.
• Pipeline Burst Cache: A type of memory cache built into many modern DRAM controller and chipset designs. Pipeline burst caches use two techniques – a burst mode that pre-fetches memory contents before they are requested, and pipelining so that one memory value can be accessed in the cache at the same time that another memory value is accessed in DRAM. The purpose of pipeline burst caches is to minimize wait states so that memory can be accessed as fast a possible by the microprocessor.
• Pipelining: A processor performance enhancement process that allows for a second instruction to be performed before the first has completed. This process produces a steady stream of information and greatly increases the productivity of the processor.
• Pixel: Short for Picture Element, a pixel is a single point in a graphic image. Graphics monitors display pictures by dividing the display screen into thousands (or millions) of pixels, arranged in rows and columns. The pixels are so close together that they appear connected.
The number of bits used to represent each pixel determines how many colors or shades of gray can be displayed. For example, in 8-bit color mode, the color monitor uses 8 bits for each pixel, making it possible to display 2 to the 8th power (256) different colors or shades of gray.
On color monitors, each pixel is actually composed of three dots — a red, a blue, and a green one. Ideally, the three dots should all converge at the same point, but all monitors have some convergence error that can make color pixels appear fuzzy.
The quality of a display system largely depends on its resolution, how many pixels it can display, and how many bits are used to represent each pixel. VGA systems display 640 by 480, or about 300,000 pixels. In contrast, SVGA systems display 1,024 by 768, or nearly 800,000 pixels. True Color systems use 24 bits per pixel, allowing them to display more than 16 million different colors.
• Platform: A combination of hardware and operating system you use, for example, the “NT platform” is a PC running the Microsoft Windows NT operating system and the “PPC platform” is a Macintosh computer with a PowerPC processor running the Mac operating system.
• PLD: (Programmable Logic Device) A digital integrated circuit that can be programmed by the user to perform a wide variety of logical operations.
• Plotter: A computer output device that draws images on paper using a pen. A plotter draws real lines rather than simulating them as a conventional printer would by producing a series of very close dots.
• Plug-In: This is a program that your browser uses to manipulate a downloaded file. It differs from a Helper Application in that the plug-in works inside the browser window.
• PNP: Short for Plug and Play, a technology developed by Microsoft and Intel that supports plug-and-play installation. PnP is built into the Windows 95 operating system, but to use it, the computer’s BIOS and expansion boards must also support PnP.
• Port:
This is the connecting component or hardware that allows two computers to attach to one another.
• Portal: A web site that aims to be an entry point to the World-Wide Web, typically offering a search engine and/or links to useful pages, and possibly news or other services. These services are usually provided for free in the hope that users will make the site their default home page or at least visit it often. Popular examples are Yahoo and MSN. Most portals on the Internet exist to generate advertising income for their owners, others may be focused on a specific group of users and may be part of an intranet or extranet. Some may just concentrate on one particular subject, say technology or medicine, and are known as a vertical portals.
• POST: Short for power-on self test, a series of diagnostic tests that run automatically when you turn your computer on. The actual tests can differ depending on how the BIOS is configured, but usually the POST tests the RAM, the keyboard, and the disk drives. If the tests are successful, the computer boots itself. If the tests are unsuccessful, the computer reports the error by emitting a series of beeps and possibly displaying an error message and code on the display screen. The number of beeps indicates the error, but differs from one BIOS to another.
• POP: Point of Presence, also Post Office Protocol Two commonly used meanings: A Point of Presence usually means a city or location where a network can be connected to, often with dial up phone lines. So if an Internet company says they will soon have a POP in Belgrade, it means that they will soon have a local phone number in Belgrade and/or a place where leased lines can connect to their network.
A second meaning, Post Office Protocol refers to a way that e-mail client software, such as Outlook, gets mail from a mail server. When you obtain an account from an Internet Service Provider (ISP) you almost always get a POP account with it, and it is this POP account that you tell your e-mail software to use to get your mail. Another protocol called IMAP is replacing POP for email.
• Primary Cache: Primary cache is the cache located closest to the CPU. Usually, primary cache is internal to the CPU, and secondary cache is external. Some early-model personal computers have CPU chips that don’t contain internal cache. In these cases the external cache, if present, would actually be the primary (L1) cache.
• Primary Key:
A set of one or more values in a database that uniquely identifies a record in a table.
• Primitive: This refers to low-level objects or older older objects that can be introduced in to a higher-level object to construct a more complex object.
• Proof Theory: This deals with the actual “logic” of the programming. Using mathematical analysis techniques, the programming language is proof checked.
• Processor: A processor is a device that processes programmed instructions and performs tasks. Your processor sends and receives information from the different parts of the system (from hardware and software). The speed at which the CPU processes information internally is measured in MegaHertz (MHz) and GigaHertz (GHz). 1 GHz is equal to 1,000 MHz.
• Programmable Read-Only Memory (PROM): A special memory chip that is blank when first purchased. It can be written to by the user by using a special hardware programmer. Once the data is written to it, it cannot be erased or changed.
• Protocol:
An agreed-upon format for transmitting data between two devices. The protocol determines the following:
-The type of error checking to be used. -Data compression method, if any. -How the sending device will indicate that it has finished sending a message. -How the receiving device will indicate that it has received a message.
There are a variety of standard protocols from which programmers can choose. Each has particular advantages and disadvantages; for example, some are simpler than others, some are more reliable, and some are faster. From a user’s point of view, the only interesting aspect about protocols is that your computer or device must support the right ones if you want to communicate with other computers. The protocol can be implemented either in hardware or in software.
• Proxy Server: A server that acts as an intermediary between a workstation user and the internet so that the enterprise can ensure security, administrative control, and caching service. A proxy server is associated with, or part of, a gateway server that separates the enterprise network from the outside network and a firewall server that protects the enterprise network from the outside intrusion.
• PS/2 Port: A type of port developed by IBM for connecting a mouse or keyboard to a PC. The PS/2 port supports a mini DIN plug containing just 6 pins. Most PCs have a PS/2 port so that the serial port can be used by another device, such as a modem. The PS/2 port is often called the mouse port.
• PXE: Pre-boot eXecution Environment. (pronounced “pixie”) Created by Intel, it is one of their WfM specification components. A PXE-enabled workstation has a jumper that connects its NIC to the LAN which will keep the workstation connected to the network even when there is no power. Having this installed jumper, the system administrator will not have to physically visit this workstation to load software or run diagnostic programs. It is all done over the network.
• QAM: Quadrature Amplitude Modulation. A method of modulating digital signals using both amplitude and phase coding. Used for downstream and can be used for upstream.
• QPSK: Quadrature Phase-Shift Keying. A method of modulating digital signals using four phase states to code two digital bits per phase shift.
• Quartz: A powerful graphics system that delivers a rich imaging model, on-the-fly rendering, anti-aliasing, and compositing of PostScript graphics. Quartz also implements the windowing system for Mac OS X and provides low-level services such as event handling and cursor management. It also offers facilities for rendering and printing that use PDF as an internal model for graphics representation.
• Query:
This is to make a computer request of a database.
• QuickTime Player: A multimedia technology developed by Apple Computer. Developed to display video, sound, animation, graphics, text, music and 360 degree virtual reality (VR) scenes. Apple makes its QuickTime plug-in available for free and once installed on your computer system, you can watch streaming media within a web page.
• Radio Frequency Identification: RFID first appeared in tracking and access applications during the 1980s. It is a method of remotely storing and retrieving data using devices called RFID tags/transponders and is coming into increasing use as an alternative to the bar code.
• RAID: Short for Redundant Array of Independent (or Inexpensive) Disks, a category of disk drives that employ two or more drives in combination for fault tolerance and performance. RAID disk drives are used frequently on servers but aren’t generally necessary for personal computers.
There are number of different RAID levels. The three most common are 0, 3, and 5:
Level 0: Provides data striping (spreading out blocks of each file across multiple disks) but no redundancy. This improves performance but does not deliver fault tolerance.
Level 1: Provides disk mirroring.
Level 3: Same as Level 0, but also reserves one dedicated disk for error correction data. It provides good performance and some level of fault tolerance.
Level 5: Provides data striping at the byte level and also stripe error correction information. This results in excellent performance and good fault tolerance.
• RAM:
(Random Access Memory) A configuration of memory cells that hold data for processing by a computer’s central processing unit, or CPU; (see also memory). The term random derives from the fact that the CPU can retrieve data from any individual location, or address, within RAM.
• Ranging: The process of automatically adjusting transmit levels and time offsets of individual modems, in order to make sure the bursts coming from different modems line up in the right timeslots and are received at the same power level at the CMTS.
• RAS: Short for Remote Access Services, a feature built into Windows NT that enables users to log into an NT-based LAN using a modem, X.25 connection or WAN link. RAS works with several major network protocols, including TCP/IP, IPX, and Netbeui.
To use RAS from a remote node, you need a RAS client program, which is built into most versions of Windows, or any PPP client software. For example, most remote control programs work with RAS.
• RDRAM: Rambus DRAM technology is a system-wide, chip-to-chip interface design that allows data to pass through a simplified bus. Rambus uses a unique RSL (Rambus Signaling Logic) technology. Rambus is available in two flavors: RDRAM and Concurrent RDRAM. RDRAM is currently in production with Concurrent RDRAM production scheduled for late 1997. The third line extension, Direct RDRAM, is in development stages and scheduled for production in 1999. In late 1996, Rambus agreed to a development and license contract with Intel that will lead to Intel’s PC chip sets supporting Rambus memory starting in 1999.
• RealAudio: This is a method of playing sounds invented by Rob Glasser that creates a buffer between the supplying server and your computer. The file is played without downloading it completely.
• Real Player:
Developed by RealNetworks, this is a cross-platform multi-media player.
• Real Time: This is method of processing data the moment it is received. Batch mode is a term used for a mainframe computer dealing with data when it has the time.
• Reboot: To restart a computer. In DOS, you can reboot by pressing the Alt, Control and Delete keys simultaneously. This is called a warm boot. You can also perform a cold boot by turning the computer off and then on again.
On Macs, you reboot by selecting the “Restart” option from the Special menu.
• Redundant: Array of Inexpensive (or Interconnected) Disks. A performance enhancing method of storing the same data in different places on multiple hard disks. Unnecessary redundancy can cause problems if one copy of the data is updated and another copy of the data is not. All redundant data can’t be eliminated in most databases because primary keys in one table are repeated in other tables as foreign keys to create links between tables. This type of redundancy is called controlled redundancy.
• Refresh: Generally, to update something with new data. For example, some Web browsers include a refresh button that updates the currently display Web pages. This feature is also called reload. To recharge a device with power or information. For example, dynamic RAM needs to be refreshed thousands of times per second or it will lose the data stored in it.
Similarly, display monitors must be refreshed many times per second. The refresh rate for a monitor is measured in hertz (Hz) and is also called the vertical frequency, vertical scan rate, frame rate or vertical refresh rate. The old standard for monitor refresh rates was 60Hz, but a new standard developed by VESA sets the refresh rate at 75Hz for monitors displaying resolutions of 640×480 or greater. This means that the monitor redraws the display 75 times per second. The faster the refresh rate, the less the monitor flickers.
• Refresh Rate: Refers to the speed in which an image can be flashed or re-drawn on a monitors screen. The higher the refresh rate, the more unnoticeable the flashing will be to the naked eye. A low refresh rate will make the imagery appear very unsteady or jerky. The typical refresh rate in the United States is 60 hertz (Hz).
• Registered Memory: This memory uses “registers” which are extra chips designed to delay the flow of data. By delaying the data flow, it allows for better control over communication in systems with heavily loaded memory.
• Registry: In a Windows operating system, the registry is the database of information that stores all of the setup, user preferences, software and hardware configuration information.
• Relational Database: A method in which data is stored in multiple tables so that the data can be organized by pre-defined relationships.
• Repeater: A device that receives weak incoming signals, boosts the signal and then retransmits the signal. Its purpose is to extend the signals distance while keeping adequate signal strength.
• Resolution: Refers to the sharpness and clarity of an image. The term is most often used to describe monitors, printers, and bit-mapped graphic images. In the case of dot-matrix and laser printers, the resolution indicates the number of dots per inch. For example, a 300-dpi (dots per inch) printer is one that is capable of printing 300 distinct dots in a line 1 inch long. This means it can print 90,000 dots per square inch.
For graphics monitors, the screen resolution signifies the number of dots (pixels) on the entire screen. For example, a 640-by-480 pixel screen is capable of displaying 640 distinct dots on each of 480 lines, or about 300,000 pixels. This translates into different dpi measurements depending on the size of the screen. For example, a 15-inch VGA monitor (640×480) displays about 50 dots per inch.
Printers, monitors, scanners, and other I/O devices are often classified as high resolution, medium resolution, or low resolution. The actual resolution ranges for each of these grades is constantly shifting as the technology improves.
• Resource: Generally, any item that can be used. Devices such as printers and disk drives are resources, as is memory. In many operating systems, including Microsoft Windows and the Macintosh operating system, the term resource refers specifically to data or routines that are available to programs. These are also called system resources.
• RFID: Radio Frequency identification (ID). Refers to the technology that uses devices attached to objects that transmit data to an RFID receiver. An alternative to bar coding. Advantages include data capacity, read/write capability, and no line-of-sight requirements.
• RIMM: Rambus In-Line Memory Module. RIMM is a synchronous dynamic random access memory (RAM) module that is used on newer motherboards. RIMM’s are manufactured by Rambus Corporation.
• Ripper:
This refers to a software application capable of transferring digital audio files from a CD to a hard drive.
• RISC: Reduced Instruction Set Computer. A computer processing architecture that requires fewer instructions to run applications, thus increasing processing speed.
• RJ-11:
Short for Registered Jack-11, a four- or six-wire connector used primarily to connect telephone equipment in the United States. RJ-11 connectors are also used to connect some types of local-area networks (LANs), although RJ-45 connectors are more common.
• RJ-45: Short for Registered Jack-45, an eight-wire connector used commonly to connect computers onto a local-area networks (LAN), especially Ethernets. RJ-45 connectors look similar to the ubiquitous RJ-11 connectors used for connecting telephone equipment, but they are somewhat wider.
• ROM: Stands for Read-Only Memory. A semiconductor-based memory system that stores information permanently and does not lose its contents when power is switched off. ROMs are used for firmware, such as the BIOS used in the PC; and in some portable computers, application programs and even the operating system are being stored in ROM.
• Rootkit: A set of programs used by hackers to gain access to information contained in your operating system and can even mask its presence. The program can also be used to access computers within a network. Usually, the rootkit is written for malicious purposes.
• Router: A device that connects any number of LANs. Routers use headers and a forwarding table to determine where packets go, and they use ICMP to communicate with each other and configure the best route between any two hosts. Very little filtering of data is done through routers. Routers do not care about the type of data they handle.
• Routing Switch: A switch that also performs routing operations. Usually a switch operates at layer 2 (the Data Link layer) of the OSI Reference Model while routers operate at layer 3 (the Network layer). Routing switches, however, perform many of the layer 3 functions usually reserved for routers. And because the routing is implemented in hardware rather than software, it is faster. The downside of routing switches is that they are not as powerful or as flexible as full-fledged routers.
Because they perform some layer 3 functions, routing switches are sometimes called layer-3 switches.
• RPL: Request Parameter List. A VTAM (Virtual Telecommunications Access Method) control block that contains parameters necessary for processing a request (data transfer, connecting or disconnecting a terminal, etc).
Also, Relocatable Program Library. A data set used to store CICS (Customer Information Control System) application programs, which are fetched (loaded) at execution time.
• RSS: (Rich Site Summary)
XML format for distributing news headlines on the Web, also known as Really Simple Syndication.
• SATA: Serial Advanced Technology Attachment. A computer bus designed to transfer data to and from a hard drive using serial signaling technology. Because SATA cables are thinner than its ribbon type counterpart, they can be connected to more devices while maintaining its signal integrity.
• Scalable: Basically, a scalable system or system architecture is one that can be modified in its size or configuration to suit changing conditions. As an example, a company that is set up to run a client/server type network may only have 10 people currently set up on the network, but the company plans to have many more set up in the coming years. In this instance, they would need to be able to make this network scalable.
• Scalar Processing:
A process that calculates numbers in sequence.
• Scope: In computer programming, this would refer to a specific identifying enclosing context. Each programming language uses various types of scopes to accomplish different things.
• Screen Flicker:
This is generally referring to the flickering of a display screen and can be caused by a number of factors, the
most important of which is the monitor’s refresh rate, or the speed that the screen is re-drawn. If the refresh rate is too slow, the screen will appear to glimmer. Another factor that affects screen flicker is the persistence of the screen phosphors. Low-persistence phosphors fade more quickly than high-persistence monitors, making screen flicker more likely. Screen flicker can also be affected by lighting. Finally, screen flicker is a subjective perception that affects people differently. Some people perceive screen flicker where others do not. Most people perceive no screen flicker if the refresh rate is 72 MHz or higher.
• SCSI: Abbreviation of “Small Computer System Interface”. It is pronounced “scuzzy,” and is a parallel interface standard used by Apple Macintosh computers, PCs, and many UNIX systems for the purpose of attaching peripheral devices to computer systems. Nearly all Apple Macintosh computers, excluding only the earliest Macs and the recent iMac, come with a SCSI port for attaching devices such as disk drives and printers.
SCSI interfaces provide for faster data transmission rates (up to 80 megabytes per second) than standard serial and parallel ports. In addition, you can attach many devices to a single SCSI port, so that SCSI is really an I/O bus rather than simply an interface.
The following varieties of SCSI are currently implemented:
SCSI-1: Uses an 8-bit bus, and supports data rates of 4 MBps
SCSI-2: Same as SCSI-1, but uses a 50-pin connector instead of a 25-pin connector, and supports multiple devices. This is what most people mean when they refer to plain SCSI.
Wide SCSI: Uses a wider cable (168 cable lines to 68 pins) to support 16-bit transfers.
Fast SCSI: Uses an 8-bit bus, but doubles the clock rate to support data rates of 10 MBps.
Fast Wide SCSI: Uses a 16-bit bus and supports data rates of 20 MBps.
Ultra SCSI: Uses an 8-bit bus, and supports data rates of 20 MBps.
SCSI-3: Uses a 16-bit bus and supports data rates of 40 MBps. Also called Ultra Wide SCSI.
Ultra2 SCSI: Uses an 8-bit bus and supports data rates of 40 MBps.
Wide Ultra2 SCSI: Uses a 16-bit bus and supports data rates of 80 MBps.
• SDH: Synchronous Digital Hierarchy. A method used for multiplexing many circuits with a low bit rate onto fewer circuits with a higher bit rate, and vice-versa (de-multiplexing). Used primarily in the telecomms industry to carry telephony traffic. This network can also be used to carry IP traffic.
• SDRAM: Short for “Synchronous Dynamic Random Access Memory”. This is a newer type of DRAM that has the ability to run at much higher clock speeds than conventional memory. SDRAM actually synchronizes itself with the CPU’s bus and is capable of running at 100 MHz, about three times faster than conventional FPM RAM, and about twice as fast EDO DRAM and BEDO DRAM. SDRAM is replacing EDO DRAM in many newer computers.
Today’s fastest Pentium systems use CPU buses running at 100 MHz, so SDRAM can keep up with them, though barely. Future PCs, however, are expected to have CPU buses running at 200 MHz or faster. SDRAM is not expected to support these high speeds which is why new memory technologies, such as RDRAM and SLDRAM, are being developed.
• Secondary Cache: Also referred to as “Level 2 cache” or “L2″. In general, L2 cache memory resides on a separate external chip from the microprocessor chip. However, The Pentium Pro processor has an L2 cache on the same chip as the microprocessor.
• Semantics: A relationship between words, phrases or any other allowable constraint and their actual meaning. This is contrast to “Syntax”. An example could be; if you enter a misspelled command, it would be a syntax error, but if you enter what may be a legitimate command but is not understood in its current context, this would be a “semantics error”.
• Semiconductor:
This refers to a material that is not a good conductor of electricity (copper) nor a good insulator (plastic). Silicon and germanium are the most common semiconductor materials.
Semiconductor materials are used in computer chips, both for CPU and memory. Its purpose is to create miniature electronic components that take up less space and require less energy.
• SEO: (Search Engine Optimization) SEO is a process of arranging a web site’s content to obtain high rankings in various search engines (both the site and individual pages), and includes tailoring on-page text (such as headlines and subtitles) as well as choosing the proper keywords for a page’s meta tags.
• Serialization:
A sequence of commands that execute orders in a database.
• Serial Port: A port, or interface, that can be used for serial communication, in which only 1 bit is transmitted at a time. Most serial ports on personal computers conform to the RS-232C or RS-422 standards. A serial port is a general-purpose interface that can be used for almost any type of device, including modems, mice, and printers (although most printers are connected to a parallel port).
• Server:
This is a mainframe computer that serves the other computers attached to it.
• SGRAM: Abbreviation of “Synchronous Graphic Random Access Memory”. This is a type of DRAM used commonly on graphics accelerators and video adapters. Like SDRAM, SGRAM can synchronize itself with the CPU bus clock up to speeds of 100 MHz.
• Shadowing: A technique used to increase a computer’s speed by using high-speed RAM memory in place of slower ROM memory (RAM is about three times as fast as ROM). On PCs, for example, all code to control hardware devices, such as keyboards, is normally executed in a special ROM chip called the BIOS ROM. However, this chip is slower than the general-purpose RAM that comprises main memory. Many PC manufacturers, therefore, configure their PCs to copy the BIOS code into RAM when the computer boots. The RAM used to hold the BIOS code is called shadow RAM.
• Shareware: Software distributed on the basis of an honor system. Most shareware is delivered free of charge, but the author usually requests that you pay a small fee if you like the program and use it regularly. By sending the small fee, you become registered with the producer so that you can receive service assistance and updates. You can copy shareware and pass it along to friends and colleagues, but they too are expected to pay a fee if they use the product.
Shareware is inexpensive because it is usually produced by a single programmer and is offered directly to customers. Thus, there are practically no packaging or advertising expenses.
• Sheet Tab: In spreadsheet applications, this would refer to a tab at the bottom of a work sheet that acts as a means to identify or access different sheets within a workbook.
• Shell: Just like the shell of an egg is the outermost layer, in computer technology, this refers to the outermost layer of a program. Operating systems and applications sometimes provide an alternative shell to make interaction with the program easier. For example, if the application is usually command driven, the shell might be a menu-driven system that translates the user’s selections into the appropriate commands.
Sometimes called command shell, a shell is the command processor interface. The command processor is the program that executes operating system commands. The shell, therefore, is the part of the command processor that accepts commands. After verifying that the commands are valid, the shell sends them to another part of the command processor to be executed.
• SID (Service ID): Used in the DOCSIS standard to defines a particular mapping between a cable modem (CM) and the CMTS. The SID is used for the purpose of upstream bandwidth allocation and class-of-service management.
• SIMM:
Acronym for single in-line memory module, a small circuit board that can hold a group of memory chips. Typically, SIMMs hold up 8 (on Macintoshes) or 9 (on PCs) RAM chips. On PCs, the ninth chip is often used for parity error checking. Unlike memory chips, SIMMs are measured in bytes rather than bits. SIMMs are easier to install than individual memory chips.
The bus from a SIMM to the actual memory chips is 32 bits wide. A newer technology, called dual in-line memory module (DIMM), provides a 64-bit bus. For modern Pentium microprocessors that have a 64-bit bus, you must use either DIMMs or pairs of SIMMs.
• Simplex: A one directional communications circuit that can only either transmit or receive, but not both. Two good examples of simplex devices would be your TV or an FM radio.
• SIP: Abbreviation of single in-line package, a type of housing for electronic components in which the connecting pins protrude from one side. Compare with DIP and PGA. A SIP is also called a Single In-line Pin Package (SIPP).
• Skype: This is a peer-to-peer voice over Internet protocol (VoIP). This Internet telephony network was created by the same people that created Kazaa (Niklas Zennström and Janus Friis). It was developed as a free desktop software application that gives users the ability to make free Internet phone calls to other Skype users or you can use the application to place and receive phone calls to and from traditional phone lines for a reduced fee.
• SLIP: Stands for Serial Line Interface Protocol. This is another application that allows for a connection to another computer.
• SMS (Short Message Service): A popular wireless service that is used for sending and receiving short messages up to a maximum of 160 characters. The service is used for text messaging between cell phones that are on a GSM (Global System for Mobile) network.
• SMTP:
Stands for Simple Mail Transfer Protocol.
• SNMP: Stands for “Simple Network Management Protocol”. It was developed in 1988 and has become a standard for Internet work management and used almost exclusively in TCP/IP networks.
• Socket: In computer technology, a Socket refers to a receptacle that provides a means of communication between two processes.
• Socket 7:
Socket 7 is a connection format used on older processors such as the Cyrix M2, AMD K6 and K6-2.
• Socket 8: The Socket 8 connection format was exclusively used on Intel Pentium Pro and Pentium II OverDrive processors.
• SODIMM (Small Outline Dual Inline Memory Module): These memory modules are typically used in laptop and notebook computers where space and low power consumption is a major consideration. SODIMM’s are about half the size of its DIMM counterpart.
• Software Modem: A modem implemented entirely in software. Software modems rely on the computer’s processor to modulate and demodulate signals.
• Source Code: Computer programs or operating systems are originally written by a human being in a programming language. This is called the source code of the software. To be actually used by a computer, the program has to be translated by the computer from the source code into the machine language that the computer understands and can execute. This translation process is referred to as compiling.
• Software:
This is a program, the actual code the computer reads. All other stuff is hardware. A floppy disc is hardware.
• Spam:
This is to transmit unwanted messages, usually over email, to a great many people.
• Spoofing: To fool. In networking, the term is used to describe a variety of ways in which hardware and software can be fooled. Email spoofing, for example, involves trickery that makes a message appear as if it came from a legitimate business email address.
• Spooling: The process of storing a device (eg: printer) output signal in a queue, while the device can take on other actions. When the device is ready to take on other actions, it will draw from the queue. The term spooling is derived from the acronym “Spool”: Simultaneous Peripheral Operations On-Line
• SQL: (Structured Query Language) A specialized programming language for sending queries to databases. Most industrial-strength and many smaller database applications can be addressed using SQL. Each specific application will have its own version of SQL implementing features unique to that application, but all SQL-capable database support a common subset of SQL.
• SRAM: Short for static random access memory, and pronounced ess-ram. SRAM is a type of memory that is faster and more reliable than the more common DRAM (dynamic RAM). The term static is derived from the fact that it doesn’t need to be refreshed like dynamic RAM.
While DRAM supports access times of about 60 nanoseconds, SRAM can give access times as low as 10 nanoseconds. In addition, its cycle time is much shorter than that of DRAM because it does not need to pause between accesses. Unfortunately, it is also much more expensive to produce than DRAM. Due to its high cost, SRAM is often used only as a memory cache.
• SSL: (Secure Sockets Layer) A protocol designed by Netscape Communications to enable encrypted, authenticated communications across the Internet. SSL is used mostly in communications between Web browsers and Web servers. URLs that begin with “https” indicate that an SSL connection will be used.
• Static: As a web site term, this is used to describe a web page that is not interactive. The webmaster writes information to the source code of a web page and can only be changed by re-writing the source code. A visitor to the web page cannot manipulate its contents.
• Steganography: This refers to a method of concealing data inside of data. The secret information can be hidden inside of an image or sound file so that a normal user would not know that it existed.
• Streaming:
A technology that involves the playing of audio or video files in real time over the Internet.
• Subroutine: A procedure that performs a specific function; usually a process that may be needed several times or a routine that may be used in several different programs. For example, many subroutines have been created to parse URL-encoded data.
• Subscriber Unit (SU):
An alternate term for cable modem.
• SuperFetch: A memory management technology in Windows Vista that is designed to launch applications more quickly by getting the most out of the available RAM (random access memory). SuperFetch has the ability to learn which applications you use most often so that it can pre-load them into memory.
• SVGA:
Stands for Super Video Graphics Adapter. It’s a high level monitor.
• Swap File: A swap file is an area on your hard disk used as virtual memory. It’s called a swap file because virtual memory management software swaps data between it and main memory (RAM).
In the Windows Operating System, a temporary swap file can be configured only when the system needs it. In a Linux and Unix environment, permanent swap files are used which dedicate a certain portion of hard drive space.
• Swap Space: Disk space used by the kernel as “virtual” RAM. It is slower than RAM, but because disk space is cheaper, swap is usually more plentiful. Swap space is useful to the kernel for holding lesser-used data and as a fallback when physical RAM is exhausted.
• Switch: In networks, a device that filters and forwards packets between LAN segments. Switches operate at the data link layer (layer 2) of the OSI Reference Model and therefore support any packet protocol. LANs that use switches to join segments are called switched LANs or, in the case of Ethernet networks, switched Ethernet LANs.
A small lever or button. The switches on the back of printers and on expansion boards are called DIP switches. A switch that has just two positions is called a toggle switch.
Another word for option or parameter — a symbol that you add to a command to modify the command’s behavior.
• Switching Hub: A high-performance hub, also called a “switching hub” that can recall what devices are connected to each port and transfer necessary data to the required port. Unlike the conventional hub, which sends data to every port.
• Synchronize: Refers to two or more elements, events or operations programmed to occur at a predefined moment in time or place.
• Synchronous: Synchronous can refer to: (1) A communications method that transmits a group of characters as a block of data rather than as individual characters. (2) A reference to the fact that two different data streams are tied, or synchronized, to a single reference clock. (3) Data transmitted in a time-division multiplexer.
• Syntax: Grammatical structuring of data using a special code that defines how this special code is used to form words, phrases or any other allowable constraint.
• System: A combination of the hardware, software, and firmware. A system typically consists of components (or elements) which are connected together in order to accomplish a specific function or set of functions.
• TCP/IP: Acronym for Transmission Control Protocol/Internet Protocol, the suite of communications protocols used to connect hosts on the Internet. TCP/IP uses several protocols, the two main ones being TCP and IP. TCP/IP is built into the UNIX operating system and is used by the Internet, making it the de facto standard for transmitting data over networks. Even network operating systems that have their own protocols, such as Netware, also support TCP/IP.
• Telnet:
One of the TCP/IP Protocols. It allows a connection to another computer over dedicated phone lines.
• Terabyte: (TB) 2 to the 40th power (1,099,511,627,776) bytes. This is approximately 1 trillion bytes. 10 to the 12th power (1,000,000,000,000). This is exactly one trillion.
• Terminal:
This is what you look at when you’re on the Internet. It’s your computer screen.
• Terminator: A device attached to the end-points of a bus network or daisy-chain. The purpose of the terminator is to absorb signals so that they do not reflect back down the line. Ethernet networks require a terminator at both ends of the bus, and SCSI chains require a single terminator at the end of the chain.
A character that indicates the end of a string. In the C programming language, the null character serves as a
terminator.
• Terminal Emulation:
This is an application that allows your terminal to act as a dumb terminal.
• Thin Client: Typically, a Thin Client will have little or no software installed and does not recieve its information through a hard drive but rather from servers in a network. Since a Thin Client assumes the presence of a file server, these systems cost considerably less than a fully loaded personal computer. The word “Thin” refers to the boot image that this type of system requires.
• Thread: In online discussions, a series of messages that have been posted as replies to each other. A single forum or conference typically contains many threads covering different subjects. By reading each message in a thread, one after the other, you can see how the discussion has evolved. You can start a new thread by posting a message that is not a reply to an earlier message.
• Throughput: The amount of data transferred from one place to another or processed in a specified amount of time. Data transfer rates for disk drives and networks are measured in terms of throughput. Typically, throughputs are measured in Kbps, Mbps and Gbps.
• Time Constant:
In electronics, this term refers to a measured amount of time that current or voltage rises or falls across a circuit.
• Toggle:
A function that allows a user to switch back and fourth between an OFF and ON position.
• Top Down Testing: Also known as “Bottom Up Testing”. It exists as an incremental testing strategy to ensure that designs are correct from the very beginning. It starts by testing the user interface, while the lower hierarchy components functionality is simulated by a dummy procedure known as a “stub”. The testing continues in this manor until all of the components have been tested.
• Topology: In networking, this refers to the physical or logical arrangement of a network. Physical Topology would refer to the connecting of the cables and nodes and the Logical Topology would refer to how the information flows through the network.
• Transceiver: Short for transmitter-receiver, a device that both transmits and receives analog or digital signals. The term is used most frequently to describe the component in local-area networks (LANs) that actually applies signals onto the network wire and detects signals passing through the wire. For many LANs, the transceiver is built into the network interface card (NIC). Some types of networks, however, require an external transceiver. In Ethernet networks, a transceiver is also called a Medium Access Unit (MAU).
• Transfer Rate: The speed at which a disk drive can transfer information between its platters and your CPU. The transfer rate is typically measured in megabytes per second, megabits per second, or megahertz.
• Transparent:
Something that occurs without being known to the user.
• Transistor: A device composed of semiconductor material that amplifies a signal or opens or closes a circuit. Invented in 1947 at Bell Labs, transistors have become the key ingredient of all digital circuits, including computers. Today’s microprocessors contains tens of millions of microscopic transistors.
Prior to the invention of transistors, digital circuits were composed of vacuum tubes, which had many disadvantages. They were much larger, required more energy, dissipated more heat, and were more prone to failures. It’s safe to say that without the invention of transistors, computing as we know it today would not be possible.
• Trojan: A type of computer virus that is loaded into an unsuspecting users system via a host program such as a free game. The Trojan can be programmed by the author to perform many actions once activated by the user. These actions usually have malicious intent. The term “Trojan” comes from ancient Greece, where the Greeks used a wooden horse containing hidden Greek soldiers to gain entrance to the city of Troy.
• True Color: Refers to any graphics device or software that uses at least 24 bits to represent each dot or pixel. Using 24 bits means that more than 16 million unique colors can be represented. Since humans can only distinguish a few million colors, this is more than enough to accurately represent any color image.
• TTL (Transistor-Transistor Logic):
A digital electronics term used to describe a class of integrated circuits derived from two transistors.
• Turnkey System: A system that already contains all the components and programs required for operation. The vendor takes care of installation and configurations so all the user has to do is “turn the key” to begin using the system.
• TWAIN:
Stands for Technology Without An Interesting Name.