<architecture> A technique for constructing a processor from modules,
each of which processes one bit-field or "slice" of an operand. Bit slice
processors usually consist of an ALU of 1, 2, 4 or 8 bits and control lines
(including carry or overflow signals usually internal to the CPU). For example,
two 4-bit ALUs could be arranged side by side, with control lines between them,
to form an 8-bit ALU. A sequencer executes a program to provide data and control
The AMD Am2901 is an example.
bit rate « bit-robbing « bit rot « bit slice
» bits per inch » bits per pixel » bits per second
bits per inch
<unit> (BPI) A measure of the recording density of a magnetic tape or
bit-robbing « bit rot « bit slice « bits per inch
» bits per pixel » bits per second » bit string
bits per pixel
<hardware, graphics> (bpp) The number of bits of information stored per
pixel of an image or displayed by a graphics adapter. The more bits there are,
the more colours can be represented, but the more memory is required to store or
display the image.
A colour can be described by the intensities of red, green and blue (RGB)
components. Allowing 8 bits (1 byte) per component (24 bits per pixel) gives 256
levels for each component and over 16 million different colours - more than the
human eye can distinguish. Microsoft Windows [and others?] calls this
truecolour. An image of 1024x768 with 24 bpp requires over 2 MB of memory.
"High colour" uses 16 bpp (or 15 bpp), 5 bits for blue, 5 bits for red and 6
bits for green. This reduced colour precision gives a slight loss of image
quality at a 1/3 saving on memory.
Standard VGA uses a palette of 16 colours (4 bpp), each colour in the palette is
24 bit. Standard SVGA uses a palette of 256 colours (8 bpp).
Some graphics hardware and software support 32-bit colour depths, including an
8-bit "alpha channel" for transparency effects.
bit rot « bit slice « bits per inch « bits per
» bits per second » bit string » bit stuffing
bits per second
<communications, unit> (bps, b/s) The unit in which data rate is
For example, a modem's data rate is usually measured in kilobits per second. In
1996, the maximum modem speed for use on the PSTN was 33.6 kbps, rising to 56
kbps in 1997.
Note that kilo- (k), mega- (M), etc. in data rates denote powers of 1000, not
bit slice « bits per inch « bits per pixel « bits
per second » bit string » bit stuffing » bit
<programming, data> An ordered sequence of bits. This is very similar to
a bit pattern except that the term "string" suggests an arbitrary length
sequence as opposed to a pre-determined length "pattern".
bits per inch « bits per pixel « bits per second «
bit string » bit stuffing » bit twiddling »
<protocol> A protocol which guarantees the receiver of synchronous data
can recover the sender's clock. When the data stream sent contains a large
number of adjacent bits which cause no transition of the signal, the receiver
cannot adjust its clock to maintain proper synchronised reception. To eliminate
the possibility of such a pathological case, when a preset number of
transitionless bits have been transmitted, a bit which does cause a transition
is "stuffed" (transmitted) by the sender. The receiver follows the same protocol
and removes the stuffed bit after the specified number of transitionless bits,
but can use the stuffed bit to recover the sender's clock.
The advantage of bit stuffing is that only a bit (not a byte) is inserted in the
data stream, and that only when the content of the data stream fails to provide
a timing signal to the receiver. Thus very nearly 100% of the bits transported
are useful data. In contrast, asynchronous transmission of data "throws away" a
start bit and one or more stop bits for each data byte sent.
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bit stuffing » bit twiddling » bitty box »