<P> In programming language design, a first - class citizen (also type, object, entity, or value) in a given programming language is an entity which supports all the operations generally available to other entities . These operations typically include being passed as an argument, returned from a function, modified, and assigned to a variable . </P> <P> The concept of first - and second - class objects was introduced by Christopher Strachey in the 1960s . He did not actually define the term strictly, but contrasted real numbers and procedures in ALGOL: </P>

What is a first class citizen in programming
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