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RAID (Redundant Array of Inexpensive Disks or Redundant Array of Independent Disks)

Several methods of configuring multiple hard drives to store data to increase logical volume size and improve performance, and so that if one hard drive fails, the data is still available from another hard drive.

RAM (Random-access memory) Also known as read-write memory. Temporary memory stored on chips or modules such as SIMMs, DIMMs, RIMMs inside the computer. Information in RAM disappears when the computer's power is turned off. See also memory.

RAM drive 1] A memory area configured as a virtual hard drive, such as drive D, so that frequently used programs can be accessed faster. It is the opposite of virtual memory.

2] VDISK (virtual disk) that can be used in place of a hard or floppy disk for frequently accessed files. A RAM disk is dangerous for storing data because the contents are lost if the computer crashes or if power is turned off. Most users with extra RAM use it for a disk cache rather than as a RAM disk. See also memory.

Random Access Ability to access any particular block by going directly to it. Memory and disk devices support random access; by contrast, tape storage devices do not.

RARP (Reverse Address Resolution Protocol) Translates the unique hardware NIC addresses into IP address (the reverse of ARP)

RD or RMDIR command A DOS command to remove an unwanted directory. (for example, RD C:\OLDDIR). You must delete all files in the directory to be removed, prior to using this command.

RDRAM (Rambus ^TM DRAM) or RIMM (Rambus In-line Memory Module) RDRAM is a unique design developed by a company called Rambus, Inc. RDRAM is extremely fast and uses a narrow, high-bandwidth "channel" to transmit data at speeds about ten times faster than standard DRAM. A of 1999, Rambus technology is expected to be used as main PC memory.

Read/Write head The part of the hard disk that writes data to or reads data from a platter. It functions like a coiled wire that reacts to a changing magnetic field by producing a minute current that can be detected and amplified by the electronics of the disk drive.

Real mode A mode used by older 8088 systems whereby the CPU can only address 1MB of memory, and DOS programs can access memory address that may be used by other programs.

Real-time In computing, refers to an operating mode under which data is received and processed and the results returned so quickly as to seem instantaneous.

RECOVER command A DOS command that recovers files that where lost because of a corrupted file allocation table.

Reduced write current A method whereby less current is used to write data to tracks near the center of the disk, where the bits are closer together.

Refresh The process of periodically rewriting the data on dynamic RAM.

Refresh rate See Vertical Frequency.

Registration database A Windows 3.x database used to store configuration information. REGEDIT loads REG.DAT and displays a list of applications that Windows has registered.

Re-marked chips Chips that have been used and returned to the factory, marked again, and sent out. The surface of the chips may be dull or scratched.

Remote control Controlling a computer or other device from a remote location (for example, when a person controls a computer from another computer connected by a phone line).

Removable drives High-capacity drives, such as ZIP or Jaz drives, that have disks that can be removed lke floppy disks.

Removable Storage A type of storage which allows the actual storage media to be removed from a drive and replace it with other media. It is used for the transportation of data between computers and for data backup.

Repeater A device that amplifies weakened signals on a network.

Rescue disk A disk that can be used to start up a computer when the hard drive fails to boot.

Resistance The degree to which a device opposes or resists the flow of electricity. As the electrical resistance increases, the current decreases. (See Ohms and Resistor).

Resistor An electronic device that resists or opposes the flow of electricity. A resistor can be used to reduce the amount of electricity being supplied to an electronic component.

Resource arbitrator A Plug-and-Play component that decides which resources are assigned to which devices.

Resource management The Plug-and-Play process of allocating resources to devices at startup.

Retension A tape maintenance procedure that fast forwards and then rewinds the tape to eliminate loose spots on the tape.

RGB (Red, Green, Blue) The triad, the three colors that make up one pixel of a color monitor. See also triad

RISC chips (reduced instruction set computer) Chips that incorporate only the most frequently used instructions, so that the computer operates faster (for example, the PowerPC uses RISC chips).

RLL (Run Length Limited) A hard-disk method of encoding information magnetically that uses a scheme (GCR) to store blocks of data instead of single bits of data. It allows greater storage densities and higher transfer speeds than the other method in use (MFM).

Roaming users Users who can move from PC to PC within a Windows NT network, with their profiles following them.

ROM (Read-Only Memory) The memory chip(s) that permanently store computer information and instructions. Your computer's BIOS (basic input/output system) information is stored in a ROM chip. Some laptops even have the operating system (DOS) in ROM.

Root directory The main directory on the computer (often represented as C:\ on a hard drive), which typically contains other directories, such as Windows and MSOffice.

Route discovery When a router rebuilds its router tables on the basis of new information.

Router A device or box that connects networks. A router transfers a packet to other networks only when the packet is addressed to a station outside its network. The router can make intelligent decisions as to which network is the best route to use to send data to a distant network. See Bridge.

Router table Tables of network addresses that also include the best possible routes (regarding tick count and hop count) to these networks. See Tick count and Hop count.

RPM (Revolutions Per Minute.)

RS-232C An electrical standard for the interconnection of equipment established by the Electrical Industries Association; the same as the CCITT code V.24. RS-232C is used for serial ports.

RTF (Rich Text Format) A format in common use by word processors. It accepts both text and images, and retains text formatting and page layout.

Runtime configuration A Plug-and-Play ongoing process that monitors changes in system devices, such as the removal of a PC Card on a notebook computer or the docking of a notebook computer to a docking station.