A RAM disk, ramdisk or RAMdrive is a segment of active computer memory, RAM, which is being used as secondary storage, typically a role for a disk drive. Access times are greatly improved, because RAM disks are approximately a thousand times faster than hard disk drives. However, durability of data through power loss is completely absent, because they are made of normal volatile RAM. As a result, RAM disks lose their contents once the computer is turned off. RAM disks are great places to store temporary data or to hold uncompressed programs for short periods.

Random Access Memory (RAM) is a type of volatile computer storage whose contents can be accessed in any (i.e., random) order. This is in contrast to sequential memory devices such as magnetic tapes, discs and drums, in which the mechanical movement of the storage medium forces the computer to access data in a fixed order.

Random Access Memory Digital-to-Analog Converter (RAMDAC ) is a single chip on video adapter cards that converts digitally encoded images into analog signals to be displayed by a monitor. A RAMDAC consists of four different components: SRAM to store the color map, three digital-to-analog converters (DACs) and one for each of the monitor's red, green, and blue electron guns.

Row Address Strobe (RAS) is a signal sent by the processor to a DRAM circuit to tell it that an associated address is a row address. DRAM stores data in a series of rows and columns, and each cell where a data bit is stored has both a row and a column address. A processor uses both RAS and CAS (column address strobe) signals to retrieve data from DRAM.

A raster graphics image, also known as digital image or bitmap, is a data file or structure representing a generally rectangular grid of pixels, or points of color, on a computer monitor, paper, or other display device. The color of each pixel is individually defined; images in the RGB color space, for instance, often consist of colored pixels defined by three bytes—one byte each for red, green and blue. Less colorful images require less information per pixel; an image with only black and white pixels requires only a single bit for each pixel. Raster graphics are distinguished from vector graphics in that vector graphics represent an image through the use of geometric objects such as curves and polygons.

Remote Direct Memory Access (RDMA) is a communication technique whereby two or more computers communicate via Direct Memory Access directly from the main memory of one system to the main memory of another. As there is no CPU, cache, or context switching overhead needed to perform the transfer, and transfers can continue in parallel with other system operations, this is particularly useful in applications where high throughput, low latency networking is needed such as in massively parallel Linux clusters. The most common RDMA implementation is over InfiniBand.

Rambus DRAM (RDRAM) is a type of memory (DRAM) developed by Rambus, Inc. Whereas the fastest current memory technologies used by PCs (SDRAM) can deliver data at a maximum speed of about 100 MHz, RDRAM transfers data at up to 800 MHz.

Rectifier is an electrical device, comprising one or more diodes arranged for converting alternating current (AC) to direct current (DC). Rectifier allows current to pass in one direction yet blocks the flow of current in the other direction. A PC PSU typically contains a rectifier.

In computing, register is a special high-speed storage area within the CPU for data be processed by the CPU. For example, if two numbers are to be multiplied, both numbers must be in registers, and the result is also placed in a register.

Registered memory (also called buffered memory) contains registers that hold the data for one clock cycle before it is moved on to the motherboard. Registered memory is slightly slower than unregistered/unbuffered memory, and more expensive as well, so it is usually found only in applications where the need for scalability and stability outweighs the need for speed and a low price. Registered memory should not be confused with ECC memory; although many server-grade memory modules are both ECC and registered, there are registered non-ECC modules and non-registered ECC modules.