Computer are great at repetitive tasks. The most beautiful and concise
way of expressing this is Kleene's star: the symbol *, which
stands for zero or more repetitions. For example, the letter
capital A followed by the Kleene Star means either {} (the
empty string), A (the string with one A), AA (the string
with two As), and even includes the string with infinitely many As.
A related, although slightly different concept, is a wildcard
character where the star itself is the placeholder, instead of a
sign of repetition. So called "glob expressions" are common in
command line interfaces e.g. for listing all files that end with the
suffix txt: ls *.txt Wildcards are also common in daily life, a
prominent example is "blah blah".
Stephen Kleene was a mathematician studing symbolic logic. In that context there is a need to specify how well-formed expressions must be structured. The use of the Kleene star enables for generic specifications that are valid for an unbounded number of expressions.
cft, 2019-02-26