Block (programming): Difference between revisions

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In [[computer programming]], a '''statement block''' is a section of [[computer code|code]] which is grouped together, much like a [[paragraph]]; such blocks consist of one, or more, [[statement (programming)|statements]]s. In [[C (programming language)|C]], [[C++]], and some other languages, statement blocks are enclosed by [[bracket|brace]]s <tt>{}</tt>. In [[Ada programming language|Ada]], [[Pascal programming language|Pascal]], and some other languages, blocks are denoted by "begin" and "end" statements. In [[Python programming language|Python]] they are indicated by indentation (the ''[[Off-side rule]]''). Unlike paragraphs, statement blocks can be nested; that is, with one block inside another. Blocks often define the [[Scope_(programming)|scope]] of the identifiers used within.

Blocks often have subtle but important differences in semantics. In languages in the C tradition, they define identifier scope. In C++ they can be used to define object lifetime (creation and destruction). In some languages (such as [[Pico (programming language)|Pico]]) they are merely used for grouping expressions without notions of variable scope. In languages such as [[Smalltalk]], blocks are objects in their own right, extended with a reference to their environment of definition, i.e. [[closure (computer science)|closures]].