Data Dictionary - Q-R

Q

R

  • Quadbit
  • Query
  • Radix
  • RAID
  • RAM
  • Raster
  • Real Storage
  • Reentrant Code
  • Repository
  • Resource Data
  • RLL
  • Rollback
  • ROM
  • ROM Card
  • PRM

Quadbit
A set of 4 bits representing one of 16 posible combinations. In communications, quadbits are used by modems that use quadrature amplitude modulation and operate at speeds of 2400 bits per second or more. Quadbits are a means of increasing transmission rates by encoding 4 bits at a time, rather than 1 or 2. The 16 quadbits are 000,0001,0010,0011,0100,0101,0110,0111,1000,1001,1010,1011,1100,1101,1110, and 1111.

Query
The process of extracting data from a database and presenting it for use. Also, a specific set of instructions for extracting particular data repetitively. In this latter context, for example, a query might be created to present sales figures for a particular region of the country. This query could be run periodically to obtain current reports.

R

Radix
The base of a number system – for example, 2 in the binary system, 10 in the decimal system, 8 in the octal system, and 16 in the hexadecimal system.

RAID
Redundant Arrays of Inexpensive Disks. Read more here.

RAM
Pronounced “ram.” Acronym for random access memory. Semiconductor-based memory that can be read and written by the microprocessor or other hardware devices. The storage locations can be accessed in any order. Note that the various types of ROM memory are capable of random access. The term RAM, however, is generally understood to refer to volatile memory, which can be written as well as read.

Raster
A rectangular pattern of lines; on a video display, the horizontal scan lines from which the term raster scan is derived.

Real Storage
Also called physical storage or physical memory. The amount of RAM memory in the system, as opposed to virtual memory.

Reentrant Code
Code written so that it can be shared by several programs at the same time. When a program is executing reentrant code, another program can interrupt the execution and can then start of continue execution of that same code. Many operating-system routines are written to be reentrant so that only one copy needs to reside in memory to service all executing programs.

Repository
A collection of information about a computing system; a superset of a data dictionary.

Resource Data
The data structures, templates, definition procedures, management routines, icon maps, and so forth associated with a particular resource such as menu, window, or dialog box.

RLL
Stands for run length limited, an encoding method used to store data in hard disks and floppy disks.

Rollback
A return to a previous stable condition, as when the contents of a hard disk are restored from a backup after a destructive hard disk error.

ROM
Read Only Memory. An electronic chip that stores program/data needed for a device or system to operate. Data is permanently written into the chip and only allow reading subsequently.

ROM Card
A plug-in module that contains one or more printer fonts, programs, or games or other information stored in ROM (read-only memory). A typical ROM card is about the size of a credit card and several times thicker. It stores information directly on integrated circuit boards.

RPM
Revolution per minutes.

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