In computer programming, a block of source code is a grouping of statements that execute in sequential order, top to bottom. The block structure is fundamental to structured programming, where control structures are formed with blocks. Syntactically, a block acts much like a single statement in that a control structure generally operates either on a single statement or a block.
The nature of a block varies by programming language, but there are typical features. A block usually provides for visibility scope such that an identifier defined in a block is not visible in outer, containing blocks, but is visible in inner, nested blocks unless it is masked by an identifier with the same name. A block usually provides for lifetime scope such that resources associated with an identifier are partially or fully released when control flow reaches the end of the block in which the identifier was defined.
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