Page 77 - Concise Encyclopedia of Robotics

DATA COMPRESSION D
Data compression is a method of maximizing the amount of digital infor-
mation that can be stored in a given space, or sent in a certain period
of time.
Text and program files can be compressed by replacing often-used
words and phrases with symbols such as =, #, &, or @, as long as none of
these symbols occurs in the uncompressed file.When the data are received,
they are uncompressed by substituting the original words and phrases for
the symbols.
Digital images can be compressed in either of two ways. In lossless
image compression, detail is not sacrificed; only the redundant bits are
eliminated. In lossy image compression, some detail is lost, although the
loss is usually not significant.
Text and programs can generally be reduced in size by about 50 percent
by means of data compression. Images can be reduced to a much larger
extent if a certain amount of loss can be tolerated. Some advanced image-
compression schemes can output a file that is only a tiny fraction of the
original file size.

DATA CONVERSION
Many communications systems “digitize” analog signals at the source
(transmitting end) and “undigitize” the signals at the destination (receiv-
ing end). Digital data can be transferred bit by bit (serial) or in bunches
(parallel). Data conversion is the process of altering data between analog
and digital forms, or between parallel and serial forms.

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