Scope (computer science) in the context of Code block

Scheme is a dialect of the Lisp family of programming languages. Scheme was created during the 1970s at the MIT Computer Science and Artificial Intelligence Laboratory (MIT CSAIL) and released by its developers, Guy L. Steele and Gerald Jay Sussman, via a series of memos now known as the Lambda Papers. It was the first dialect of Lisp to choose lexical scope and the first to require implementations to perform tail-call optimization, giving stronger support for functional programming and associated techniques such as recursive algorithms. It was also one of the first programming languages to support first-class continuations. It had a significant influence on the effort that led to the development of Common Lisp.

The Scheme language is standardized in the official Institute of Electrical and Electronics Engineers (IEEE) standard and a de facto standard called the Revised Report on the Algorithmic Language Scheme (RnRS). A widely implemented standard is R5RS (1998). The most recently ratified standard of Scheme is "R7RS-small" (2013). The more expansive and modular R6RS was ratified in 2007. Both trace their descent from R5RS; the timeline below reflects the chronological order of ratification.

In computer programming, an automatic variable is a local variable which is allocated and deallocated automatically when program flow enters and leaves the variable's scope. The scope is the lexical context, particularly the function or block in which a variable is defined. Local data is typically (in most languages) invisible outside the function or lexical context where it is defined. Local data is also invisible and inaccessible to a called function, but is not deallocated, coming back in scope as the execution thread returns to the caller.

Automatic local variables primarily applies to recursive lexically scoped languages. Automatic local variables are normally allocated in the stack frame of the procedure in which they are declared. This was originally done to achieve re-entrancy and allowing recursion, a consideration that still applies today. The concept of automatic variables in recursive (and nested) functions in a lexically scoped language was introduced to the wider audience with ALGOL in the late 1950s, and further popularized by its many descendants.

In programming languages, name binding is the association of entities (data and/or code) with identifiers. An identifier bound to an object is said to reference that object. Machine languages have no built-in notion of identifiers, but name-object bindings as a service and notation for the programmer is implemented by programming languages. Binding is intimately connected with scoping, as scope determines which names bind to which objects – at which locations in the program code (lexically) and in which one of the possible execution paths (temporally).

Use of an identifier id in a context that establishes a binding for id is called a binding (or defining) occurrence. In all other occurrences (e.g., in expressions, assignments, and subprogram calls), an identifier stands for what it is bound to; such occurrences are called applied occurrences.

ALGOL 58, originally named IAL, is a member of the ALGOL family of computer programming languages. It was an early compromise design soon superseded by ALGOL 60. According to John Backus:

ALGOL 58 introduced the fundamental notion of the compound statement, but it was restricted to control flow only, and it was not tied to identifier scope in the way that Algol 60's blocks were.