Glossary of Acronyms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

DAC - A device that reconstructs analog voltage waveforms from an incoming sequence of binary digits. Does not in itself introduce noise. A hardware device (in its simplest form, nothing more than a set of interconnected resistors) which converts a digital number into an analog signal whose voltage is proportional to the value of the digital number. VGA and later color video boards use DACs to convert color values into the analog signals sent to the display; sound boards normally use DACs as well.

DAT - Digital Audio Tape. A tape backup format.

DCC - Display Combination Code. A number which indicates both the type of display adapter board and the type of monitor attached to the video board.

DDC1 - Display Data Channel 1. A compliant PnP feature that communicates the monitors model, make, frequency, range, and preset resolutions to the graphics adapter circuitry on the motherboard. The graphics adapter must also be DDC 1 compliant.

DDC2B - Display Data Channel 2B. A faster version of DDC 1 that permits the computer operating system to query the monitor and determine its features.

DDO - Dynamic Drive Overlay.

DIB - Dual Independent Bus. A two bus CPU-memory system employed by Intel on the Pentium Pro and Pentium II Processor to increase I/O bandwidth to the CPU. This consisted of a dedicated CPU to main memory bus, and CPU to L2 cache bus.

DIMM - Duel Inline Memory Module. Memory modules that will someday replace the SIMM. DIMMS have 168 pins, are eight inches long, and are installed individually.

DIN - Deutch Industry Norm. A type of plug normally used for the keyboard to plug into the computer. DIN come in five to nine pin configurations, although five and six pin are the most common.

DIX - Digital Intel Xerox Connector. A type of connector used in the thicknet Ethernet architecture.

DMA - Direct Memory Access. A channel for direct memory access that does not involve the microprocessor, providing data transfer directly between memory and a disk drive. Very useful in operating systems with multitasking capabilities. There are a set of DMA controller chips on the mainboard. Each DMA circuit has a level number and can support one device. When installing new adapters, it is important to avoid conflicts for the DMA number just as one avoids conflicts for the I/O address or interrupt level. A program stores into the DMA circuit a starting memory buffer address and length. When the device is ready for more data, it uses one bus cycle to send a request to the DMA chip. The chip then substitutes for the CPU in generating the next buffer address to the memory circuits to fetch the next chunk of data for the device. The CPU can be running other programs. However, that first signal from the device to the DMA chip takes one more bus cycle than ordinary Programmed I/O. Thus DMA has not been attractive for disk, LAN, and other performance critical I/O.

DPI - Dots Per Inch. The standard used to measure print device resolution. The greater the DPI, the better the resolution.

DPMI - A specification that allows multiple applications to have access to memory at the same time.

DRAM - Dynamic Random Access Memory. . The type of memory the typical PC uses. The speed of DRAM is measured in nsec. DRAM are fast page mode RAM. DRAM uses internal capacitors to store data (a single transistor turns it on of off) which lose their charge over time, so they need constant refreshing to retain information, otherwise 1s will turn to 0s. The end result is that between every memory access is sent an electrical charge that refreshes the chip's capacitors to keep data in a fit state, which cannot be reached whilst recharging is going on. Reading a DRAM discharges its contents, so they have to be written back to immediately to keep the sane information.

DSP - Digital Signal Processor. A processor that is optimized for performing the complex mathematical calculations inherent in processing digital signals. A discrete DSP may be reprogrammed. A DSP integrated in a chip set typically contains its own ROM and cannot be reprogrammed.

DVD - Digital Video Disk. New variation of the compact disc incorporating new technologies capable of holding large amounts of data. DVD's can currently hold up to 4.7 GB.

DSVD - Digital Simultaneous Voice/Data. A digital communications technology that comes with video phone capabilities allowing for video, voice, and to be shared simultaneously over high speed connections.

DX - IBM compatible CPU in the 80386 series with a math coprocessor and a 32 bit bus structure. There was a DX2 and a DX4 model.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Compiled by Scott McArdle, MagnaCom Limited. I hope this list has helped you and if there is an item that should be on this list, please let me know. Thanks. PS, I've spent 100's of hours maintaining this list, please don't be a LAMER.