random

1. Unpredictable (closest to mathematical definition); weird. "The system's been behaving pretty randomly."

2. Assorted; undistinguished. "Who was at the conference?" "Just a bunch of random business types."

3. (pejorative) Frivolous; unproductive; undirected. "He's just a random loser."

4. Incoherent or inelegant; poorly chosen; not well organised. "The program has a random set of misfeatures." "That's a random name for that function." "Well, all the names were chosen pretty randomly."

5. In no particular order, though deterministic. "The I/O channels are in a pool, and when a file is opened one is chosen randomly."

6. Arbitrary. "It generates a random name for the scratch file."

7. Gratuitously wrong, i.e. poorly done and for no good apparent reason. For example, a program that handles file name defaulting in a particularly useless way, or an assembler routine that could easily have been coded using only three registers, but redundantly uses seven for values with non-overlapping lifetimes, so that no one else can invoke it without first saving four extra registers. What randomness!

8. A random hacker; used particularly of high-school students who soak up computer time and generally get in the way.

9. Anyone who is not a hacker (or, sometimes, anyone not known to the hacker speaking). "I went to the talk, but the audience was full of randoms asking bogus questions".

10. (occasional MIT usage) One who lives at Random Hall. See also J. Random, some random X.

[Jargon File]

Last updated: 1995-12-05

random-access memory

<storage>

(RAM) (Previously "direct-access memory"). A data storage device for which the order of access to different locations does not affect the speed of access. This is in contrast to, say, a magnetic disk, magnetic tape or a mercury delay line where it is very much quicker to access data sequentially because accessing a non-sequential location requires physical movement of the storage medium rather than just electronic switching.

In the 1970s magnetic core memory was used and some old-timers still call RAM "core". The most common form of RAM in use today is semiconductor integrated circuits, which can be either static random-access memory (SRAM) or dynamic random-access memory (DRAM).

The term "RAM" has gained the additional meaning of read-write. Most kinds of semiconductor read-only memory (ROM) are actually "random access" in the above sense but are never referred to as RAM. Furthermore, memory referred to as RAM can usually be read and written equally quickly (approximately), in contrast to the various kinds of programmable read-only memory. Finally, RAM is usually volatile though non-volatile random-access memory is also used.

Interestingly, some DRAM devices are not truly random access because various kinds of "page mode" or "column mode" mean that sequential access is faster than random access.

The humorous expansion "Rarely Adequate Memory" refers to the fact that programs and data always seem to expand to fill the memory available.

Last updated: 2007-10-12

Random Access Memory Digital-to-Analog Converter

<hardware>

(RAMDAC) A combination of three fast DACs with a small SRAM used in graphics display adapters to store the colour palette and to generate the analog signals to drive a colour monitor. The logical colour number from the display memory is fed into the address inputs of the SRAM to select a palette entry to appear on the output of the SRAM. This entry is composed of three separate values corresponding to the three components (red, green, and blue) of the desired physical colour. Each component value is fed to a separate DAC, whose analog output goes to the monitor, and ultimately to one of its three electron guns (or equivalent in non-CRT displays).

DAC word lengths range usually from 6 to 10 bits. The SRAM's wordlength is three times the DAC's word length. The SRAM acts as a colour lookup table. It usually has 256 entries (and thus an 8-bit address). If the DAC's word length is also 8 bits, we have a 256 x 24-bit SRAM which allows a selection of 256 out of 16777216 possible colours for the display. The contents of the SRAM can be changed while the display is not active (during display blanking times). The SRAM can usually be bypassed and the DACs can be fed directly by display data (for true colour modes).

Last updated: 1996-03-24

randomness

1. An inexplicable misfeature; gratuitous inelegance.

2. A hack or crock that depends on a complex combination of coincidences (or, possibly, the combination upon which the crock depends for its accidental failure to malfunction). "This hack can output characters 40--57 by putting the character in the four bit accumulator field of an XCT and then extracting six bits - the low 2 bits of the XCT opcode are the right thing." "What randomness!"

3. Of people, synonymous with "flakiness". The connotation is that the person so described is behaving weirdly, incompetently, or inappropriately for reasons which are (a) too tiresome to bother inquiring into, (b) are probably as inscrutable as quantum phenomena anyway, and (c) are likely to pass with time. "Maybe he has a real complaint, or maybe it's just randomness. See if he calls back."

[Jargon File]

random number

pseudorandom number

random testing

<programming, testing>

A black-box testing approach in which software is tested by choosing an arbitrary subset of all possible input values. Random testing helps to avoid the problem of only testing what you know will work.

Last updated: 2001-04-30

Nearby terms:

RAMTRON ♦ random ♦ random-access memory ♦ Random Access Memory Digital-to-Analog Converter

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