Run-length encoding
Lossless compression encoding consecutive identical values as (value, count) pairs. Effective for images/data with long runs (faxes, graphics). Ineffective for varied data.
Real World
Fax machines use run-length encoding because scanned documents are mostly white space — a typical page line like 200 white pixels followed by 50 black compresses dramatically as '200W, 50B'.
Exam Focus
Show a worked encoding of a given data string — marks require the (value, count) pairs, not just a description of the method.
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