RFI. Many electronic devices, including computers and peripherals, can interfere with other signals in the radio-frequency range by producing electromagnetic radiation; this is normally regualated by government agencies in each country.
Redundent Array of Inexpensive Disks. In networking and truly critical applications, a method of using several hard disk drives in an array to provide fault-tolerance in the event that one or more drives fail catastrophically.
The different levels of RAID,0 through 5, are each designed for a specific use; there is no difference in speed or quality between these levels. The correct level of RAID for your installation depends on how you use your network.
A slang expression used to describe the increasing demands made upon limited memory space, especially the inability to run large application programs in a PC with 1MB of RAM running DOS.
An area of memory managed by a special device driver and used as a simulated disk.
Because the RAM disk operates in memory, it works very quickly, much faster than a regular hard disk. Remember that anything you store on your RAM disk will be erased when you turn off your computer, so you must save its contents onto a real disk first. RAM disks may also be called virtual drives.
The DOS device driver used to create a RAM disk. You must load this device driver using a DEVICE or DEVICE-HIGH in your CONFIG.SYS file.
Describes the ability of a storage device to go directly to the required memory address without having to read from the beginning every time data is requested.
There is nothing random or haphazard about random access; a more precise term is direct access. In a random-access device, the information can be read directly by accessing the appropriate memory address. Some storage devices, such as tapes, must start at the beginning to find a specific storage location, and if the information is towards the end of the tape, access can take a long time. This access method is known as "sequential access."
A device that manages an image as lines of dots. Television sets and most computer displays are raster devices, as are some electrostatic printers and plotters.
To copy program or data files from a floppy or a hard disk into a computer memory, to run the program or process the data in some way. The computer may also read your commands and data input from the keyboard.
A text file placed on a set of distribution disks by the manufacturer at the last minute that may contain important information not contained in the program manuals or online help system. Sometimes it contains information pertinent to your specific configuration.
Describes a file or other collection of information that may only be read; it may not be updated in any way or deleted.
Certain important OS files are designated as read-only files to prevent users from deleting them by accident. Also,certain types of memory (ROM), and certain devices such as CD-ROM can be read but not changed.
In DOS and OS/2, a file attribute that indicates the file can be read but cannot be updated or changed in any way; nor can you delete the file.
That part of a floppy-or hard-disk system that reads and writes data to and from a magnetic disk.
To restart the computer and reload the OS, usually after a crash.
RISC. A processor that recognizes only a limited number of assembly language instructions.
RISC chips are relatively cheap to produce and debug, as they usually contain fewer than 128 different instructions. CISC processors use a richer set of instructions, typically somewhere between 200 to 300. RISC processors are commonly used in workstations, and can be designed to run up to 70 percent faster than CISC processors.
To reinitialize a disk and destroy the original contents.
In a monitor, to recharge the phosphors on the inside of the screen and maintain the image.
In certain memory systems, dynamic RAM must be recharged so that it continues to hold its contents.
In a monitor, the rate at which the phosphors that create the image on the screen are recharged.
In programming, the specifcaton of memory location by using an expression to calculate the address, rather than explicaitly specifying the location by using its address.
removable mass storage
Any high-capacity storage device inserted into a drive for reading and weriting, then removed for storage and safekeeping. This term is not usually applied to floppy disks, but to tape- and cartridge-backup systems, and Bernoulli boxes.
In computer graphics, the conversion of an outline image into a fully-formed, three-dimensional image, by the addition of colors and shading.
In networking, a simple hardware device that moves all packets from one local area network segment to another. The main purpose of a repeater is to extend the length of the network transmission medium beyond the normal maximum cable lengths.
In DOS, a term used to describe that area of memory between 640K and 1MB, also known as upper memory. Reserved memory is used by DOS to store system and video information.
Any word that has a special meaning and therefore cannot be used for any other purpose in the same context.
The degree of sharpness of a printed or displayed image, often expressed in dpi( dots per inch)
Resolution depends on the number of elements that make up the image, either dots on a laser or pixels on a monitor; the higher the number per inch, the higher the resolution of the image appears.
The time lag between sending a request and receiving the data. Response time can be applied to a complete computer system, as in the time taken to look up a certain customer record.
The process of disassembling a hardware or software product from another company to find out how it works, with the intention of duplicating some or all of its functions in another product.
In a monochrome monitor, a display mode used to highlight characters on the screen by reversing the normal background and foreground colors.
Red-Green-Blue. a method of generating colors in a video system that uses the additive primaries method. Percentages of red, blue and green are mixed to form the colors;0 percent of the colors create black,100 percent of the colors creates white.
A color monitor that accepts separate inputs for red, blue and green color signals, and normally produces a sharper image than composite color monitors, in which information for all three colors is transmitted together.
A network topology in the form of a closed loop or circle. Each node in the network is connected to the next, and messages move in one direction around the system. When a message arrives at a node, the node examines the address information in the message. If the address matches the node's address, the message is accepted; otherwise the node regenerates the signal and places the message back on the network for the next node in the system. It is this regeneration that allows a ring network to cover much greater distances than star and bus networks. Ring networks normally use some form of token-passing protocol to regulate network traffic.
A commonly used modular telephone connector. RJ-11 is a four or six pin connector used in most connections destined for voice use. RJ-45 is the eight-pin connector used for data transmission over twisted-pair wiring.
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.
In a hierarchical directory structure, the directory from which all other directories must branch.
The root directory is created by the FORMAT command, and can contain files as well as other directories. It is wise to store as few files as possible in the root directory,because in DOS there is a limit to number of entries that the root directory can hold. Also, you cannot delete the root directory.
The backslash(\) character represents the root directory, and you can use this character to make the root directory the current directory in a single step, if you type CD\ from the system prompt.
In monitor, a form of image distortion that gives solid straight lines a twisted or helical appearance. This problem is caused by poor convergence.
A simple encryption scheme often used to scramble posts to USENET newsgroups, it makes the article unreadable until the text is decoded, and is often used when the subject matter might be considered offensive. Is the outdated??
In networking, an intelligent connecting device that can send packets to the correct local area network segment to take them to their destination. Routers link LAN segments at the network layer of the ISO/OSI model.
In asynchronous transmissions, a recommended standard interface established by the Electrical Industries Association for distances greater than 50 feet, but less than 1000 feet. The standard defines the specific lines, timing and signal characteristics used between the computer and the peripheral device.
RS(recommended standard) 449 incorporates RS-422 and RS-423; serial ports on Mac computers are RS-422 ports.
In asynchronous transmissions, a recommended standard interface established by the EIA. The standard defines the specific lines, timing and signal characteristics used between the computer and the peripheral device,and uses a 25-pin or 9-pin DB connector.
RS-232-C is used for serial communications between a computer and a peripheral such as a printer, modem, digitzing tablet, or mouse. The maximum cable limit of 50 feet can be extended by using very high quality cable, line drivers to boost the signal, or short-haul modems.
RS stands for recommended standard, and the C denotes the third revision of that standard. RS-232-C is functionally identical to the CCITT V.24 standard.
RLL encoding. An efficient method of storing information on a hard disk that effectively doubles the storage capacity of a disk when compared to older, less efficient methods such as modified frequency modulation encoding(MFM).