Appendix Glossary R

In the left margin you will find links to the glossary categorised alphabetically. Some of the pages are quite long and may take a few moments to load if you use a modem. This glossary is always being updated.

Glossary - R

RAID - "Redundant Array of Independent Disks" Why settle for a single disk drive when you can have an entire team of them working together? A RAID is an organised collection of disk drives operating as a single storage unit. A device called a "RAID controller" combines the power and capacity of the individual drives to create a larger volume (or group of volumes) that can be used to store and protect important information. Depending on the specific configuration or "level" of a RAID, the disks can be used to back each other up in real time by writing data simultaneously to different areas of the array. Benefits include: increased storage space, improved performance, built-in redundancy, and a really cool acronym.

RAM - Acronym for random access memory. An integrated circuit memory chip that allows information to be stored and retrieved by a microprocessor or controller. The information can be stored or accessed in any order, and all storage locations are equally accessible. The more RAM a computer has, the more information it can process at the same time. RAM plays very much the same role for a computer that short-term memory plays for a person, and everybody knows how important short-term memory is, especially if they're counting cards at the blackjack table. The main memory in a PC. System memory is known as DRAM (Dynamic Random Access Memory) because it constantly has to be refreshed.

RAM disk - A "phantom" drive created by setting aside a section of RAM as if it were a group of regular sectors. Access to a RAM disk is very fast but data is lost when the system is reset or turned off.

Rambus - (1) Rambus, Inc. develops and licenses high-performance memory logic and circuit design technology and provides licensees with product design, layout, and testing information. (2) Direct Rambus is a high-speed memory technology that uses a narrow 16-bit bus (Rambus channel) to transmit data at speeds up to 800MHz.

Rambus Channel - The data path of Rambus systems. Because of the narrow data width (two bytes), Rambus modules transfer data at up to 800MHz.

RAS - A memory chip signal that latches the row address of a particular location in a row-column matrix.

Raster - The rectangular portion of a display monitor where the actual image appears. The raster is usually smaller than the true dimensions of the display panel. On most modern monitors the raster can be adjusted to allow for maximum image display.

Raster Graphics - A bitmap image pattern usually in a GIF or JPEG format that fills an entire display monitor assigning colour values to every available pixel.

Rasterise - The act of converting a document from a page definition language (e.g., PostScript) to an arrangement of pixels on the page or screen. Stated simply, rasterising is the interpretation of an image from a set of digital codes into an actual visual representation. When one prints out a page from a layout or design application, the image is rasterised into an array of dots, which are then impressed upon the page. Fortunately for users, the computers do all the work when it comes to rasterisation

Raw Data - Computer input that has not been organised, categorised or formatted.

Ray Tracing - A complex technical process whereby a graphical image is enhanced and made to appear more realistic by incorporating shading, shadow, and colour. This is accomplished by simulating the way light plays on individual components of the image. Ray tracing software requires a great deal of memory and processing resources and often takes several hours to produce the end effect.

RDRAM - Also known as RAMbus memory. Bandwidth is limited to 1.6 GB/s due to the design's small 16-bit bus. DDR SDRAM provides similar performance with lower latency.

Read - To access stored data, usually by transferring it from one of many storage media such as magnetic tape or floppy disk, to a hard disk for display or processing.

Read After Write - A mode of operation that has the computer read back each sector immediately after it is written on the disk, checking that the data read back is the same as recorded. This slows disk operations, but raises reliability.

Readme File - Information contained in a software program that was not part of the users manual, usually an update, improvement, a recent development, or feature.

Read Only - Recorded computer data that is recorded and cannot be changed. Operating systems contain many read-only files.

Read Only Memory - (ROM) permanently recorded computer memory.

Read Verify - A disk mode where the disk reads in data to the controller, but the controller only checks for errors and does not pass the data on to the system.

Real Audio / Real Video - An Internet delivery model for playback of audio, video, and animations offered by an organisation called Real Networks. By equipping their web browsers with the Real Audio plug-in, users can listen to and watch these media types encoded in the Real Audio format from within the window of their web browsers. The Real Audio technology caught on right away, due in no small part to its lofty ambition of giving a state of the art computer system all the functionality of a crappy AM radio. Since its introduction, Real Audio has gained wide acceptance in the industry and is a part of many cutting edge audio/video-oriented websites.

Real Time Clock - A battery operated clock inside a computer that runs even when the computer is turned off.

RealVideo - A program developed by RealNetworks allowing users to experience streaming real time video online.

Reboot - To restart a computer for any number of reasons. Some computers have a reset switch, others will reboot using a series of key commands such as, Control, Alt, Delete and choosing to restart the computer when prompted.

Recycle Bin - Comparable to the Trash Can in the Macintosh. In the Windows environment, a folder represented on the desktop by an icon of a small recycle bin.

Red Book - A standard established by Phillips and Sony for CDs that, among other things, set the playing time of a recorded CD at 74 minutes, transferred at a rate of 150 Kbps.

Refresh - Refreshing maintains data stored in DRAM. The process of refreshing electrical cells on a DRAM component is similar to recharging batteries. Different DRAM components require different refresh methods.

Refresh Rate - The number of DRAM component rows that must be refreshed. Three common refresh rates are 2K, 4K and 8K.

Register - A high speed storage space within a CPU. The size and number of registers in the central processing unit are critical in determining the speed and power of a computer.

Registered Memory - SDRAM memory that contains registers directly on the module. The registers re-drive the signals through the memory chips and allow the module to be built with more memory chips. Registered and unbuffered memory cannot be mixed. The design of the computer memory controller dictates which type of memory the computer requires.

Removable Disk - Generally said of disk drives where the disk itself is meant to be removed, and in particular of hard disks using disks mounted in cartridges. Their advantage is that multiple disks can be used to increase the amount of stored material, and that once removed, the disk can be stored away to prevent unauthorised use.

Repaginate - To reassign a numerical sequence to the pages in a document after making changes in the text and/or graphics.

Repeater - A network device that regenerates signals so they can extend the cable length.

Reset - When all else fails in a program and it is locked solid, no commands work, the keyboard is dead, hit the RESET

Resolution - Indicates the monitor space available (i.e. 640x480, 800x600, 1024x768). The higher the resolution, the more space available, and the smaller the icons and windows will be. Also the pixel density of an image expressed in such terms as "dots per inch" or "dots per centimetre." Basically speaking, the higher the resolution, the greater the potential for image detail. It is also true that a higher resolution will make a given file take up a larger amount of disk space. It is far more important to match the resolution to the occasion than to simply strive for high resolutions in all your image files. Carrying a high resolution in a file is simply a waste of disk space if the image is going to be used only on a low resolution output device such as the computer display screen. It should also be noted that while it is possible to lower the resolution of a file, it is not possible to raise the resolution of a file without making the image size smaller. You can "res down," but you really can't "res up."

Resource - Sometimes called system resources. In operating systems such as Windows and the Macintosh, any data or function that is available to the operation of software running with the system. Memory is a major resource.

Restore - To bring a window back it its original size after having been minimised or maximised.

RFC - (Request for Comments) maintained by the Internet Task Force, a collection of notes and observations made about the Internet, beginning in the late 1960s when it was called the ARPANET. With the evolution of the medium, individuals have had the opportunity to make unofficial suggestions about various procedures and protocols as "Request for Comments." Many have evolved into Internet standards.

RGB - "Red Green Blue" RGB is one of the two prevailing colour models for use in electronic publishing. It is the means through which an image is displayed on a computer screen. RGB is based on a "subtractive" colour scheme, which means that it defines white as a state in which all three of the available colours are present in the maximum amounts, and black as a state in which all three colours are completely absent. In RGB mode, colours in between black and white are achieved by withholding or "subtracting" varying amounts of the three available colours.

Right Click - To press the button on the right hand side of a mouse. With the mouse cursor on an object, right clicking will often produce a pop-up menu that, depending on the object selected, offers options that can lead the user to open a program, cut or copy, create a shortcut, or display the properties of the selected object.

Right Justify - To orient text so it conforms to a vertical margin on the right side of a document.

RIMM Connector - A Direct Rambus memory socket.

RIMM - The trademarked name for a Direct Rambus memory module. A RIMM conforms to the DIMM form factor and transfers data 16 bits at a time.

Ring Topology - A basic networking topology where all nodes are connected in a circle, with no terminated ends on the cable.

RIP - "Raster Image Process" or "Raster Image Processor" This refers to the conversion of an image from its digital definition into the visually-oriented image that is intended. The verb "to RIP" means to send a page through the process. The noun "RIP" is used to describe the machine that does the rasterisation

RISC - Reduced Instruction Set Computer. A RISC microprocessor that has fewer, simpler instructions than its CISC counterpart. RISC instructions perform simple, rudimentary functions. The simplicity of these instructions results in a very simple microprocessor design that can execute very fast. RISC instructions are typically characterised by fix length instruction sets (for example, all instructions are 32-bits each).

RJ11 - A standard telephone modular connector.

RJ45 Jack - The connector on the back of a computer or printer that accepts the RJ-45 plug; looks much like a modular telephone jack.

RJ45 Plug - The connector on the end of 10BASE-T or 100BASE-T twisted-pair cabling; looks much like a modular telephone plug.

RLL - Acronym for run length limited. A method used on some hard disks to encode data into magnetic pulses. RLL requires more processing, but stores almost 50 percent more data per disk than the older MFM (modified frequency modulation) method.

Robot - 1. a computerised machine designed for a wide variety of manufacturing functions such as material handling and automobile assembly. 2. often referred to as bot, a computer program that automatically searches, and compiles data or responds to queries such as email. ListBot is a robot of this type.

ROM - Acronym for read only memory. Integrated circuit chip containing programs and data that can be accessed and read but cannot be modified. These are special chips in the computer that contain instructions. BIOS are stored here. These are read-only files and the information cannot be changed.

Root Directory - This is the primary directory on every DOS disk. Other directories or subdirectories branch off of this one: like on a "family tree"! The

Rotational Latency - The delay between when the controller starts looking for a specific block of data on a track and when that block rotates around to where it can be read by the read/write head. On average, it is half of the time needed for a full rotation (which depends on the rotational speed, or rpm, of the disk).

Router - A complex network device used to connect two or more networks together. A router reads information sent along the network and determines its correct destination.

Router - A device that directs the flow of data among different computer devices. A router is basically the "traffic cop" of a network, but without the whistle or the funny hat.

RPM - (Revolutions Per Minute) the number of revolutions a disk turns per minute.

RTC - Real Time Clock, which is responsible for keeping track of the system time.