Select the first letter of the word from the list above to jump to appropriate section of the glossary or type the term on which you want to search.

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radio buttons

one of a group of items or options appearing in a dialog box or drop-down menu, that once selected, inactivates the others, unlike items available in a check box, of which more than one may be chosen.

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RADIUS

(Remote Authentication Dial-In User Service) a system used by some Internet Services Providers (ISPs) that requires a user to enter a user name and password. This lets the ISP know the user is authorized to access the service and allows the service to track time spent connected.

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ragged margin

in a text document, a margin that does not line up vertically. The margins in this book are left justified with regard to the terms and definitions and ragged on the right.

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RAID

(Redundant Array of Independent Disks) A disk subsystem that is used to increase performance or provide fault tolerance or both. RAID uses two or more ordinary hard disks and a RAID disk controller. In the past, RAID has also been implemented via software only. In the late 1980s, the term stood for "redundant array of inexpensive disks," being compared to large, expensive disks at the time. As hard disks became cheaper, the RAID Advisory Board changed "inexpensive" to "independent".

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RAM

(Random Access Memory) pronounced ramm, computer hardware that stores and accesses data as needed from any location within the memory on a short term basis. RAM holds needed information from the application currently running, allowing for quick access as it is called up. The data stored in RAM is cleared when the computer is shut down. There are two types of RAM. Dynamic RAM and Static RAM. (DRAM and SRAM) To facilitate its own functioning, DRAM requires an electrical charge, which is refreshed thousands of times each second while in use. While SRAM is faster because it doesn’t need to be refreshed, it is considerably more expensive than DRAM. Because of its higher speed, SRAM is often used for caching. RAM refers to a computer’s main memory as opposed to read-only memory (ROM), which contains necessary pre-recorded data used for booting the computer and other routine functions. see DRAM, SDRAM SRAM, ROM.

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RAM disk

a portion of RAM (random access memory) used to simulate a disk drive. Utilizing RAM in this way allows for quicker access to information than calling it from the hard disk, but has some limitations. First, files must be copied from the hard disk to the RAM disk for each session and the new material must be copied back to the hard disk before ending the session. This is necessary because, like normal RAM, a RAM disk clears all data when the computer is shut down. Additionally, a power failure will cause the loss of data on a RAM disk.

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rapid application development

a programming procedure that allows programmers to create usable programs quickly. Software designers are able to use a wide variety of development tools to construct graphical user interface applications that might otherwise require large development teams.

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RAS

(Remote Access Services) a component of Windows NT that allows a user to connect to a LAN using a modem, WAN link, or X.25 connection.

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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.

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raster graphics

a bitmap image pattern usually in a GIF or JPEG format that fills an entire display monitor assigning color values to every available pixel.