Editing ALGOL W (section)

== Syntax and semantics ==
ALGOL W's [[Syntax (programming languages)|syntax]] is built on a subset of the [[EBCDIC]] [[character encoding]] set. In [[ALGOL 60]], reserved words are distinct lexical items, but in ALGOL W they are only sequences of characters, and do not need to be [[Stropping (syntax)|stropped]]. Reserved words and identifiers are separated by spaces.<ref name="Stanford"/> In these ways ALGOL W's syntax resembles that of [[Pascal (programming language)|Pascal]] and later languages.

The ''ALGOL W Language Description''<ref name="description">{{cite report |last1=Bauer |first1=Henry R. |last2=Becker |first2=Sheldon I. |last3=Graham |first3=Susan L. |last4=Satterthwaite |first4=Edwin H. |last5=Sites |first5=Richard L. |date=June 1972 |title=ALGOL W Language Description |url=https://www.algol60.org/docsW/algolw.pdf}}</ref> defines ALGOL W in an [[affix grammar]] that resembles [[Backus–Naur form]] (BNF). This [[formal grammar]] was a precursor of the [[Van Wijngaarden grammar]].<ref name="Wirth"/><ref>{{cite report |last=van Wijngaarden |first=Adriaan |author1-link=Adriaan van Wijngaarden |date=22 October 1965 |title=Orthogonal Design and Description of a Formal Language: MR76 |url=http://web.eah-jena.de/~kleine/history/languages/VanWijngaarden-MR76.pdf |publisher=Mathematical Centre |place=[[Amsterdam]], Netherlands |via=Ernst-Abbe-Hochschule [[Jena]], University of Applied Sciences, Germany |access-date=2020-10-07 |archive-date=29 October 2019 |archive-url=https://web.archive.org/web/20191029151436/http://web.eah-jena.de/%7Ekleine/history/languages/VanWijngaarden-MR76.pdf |url-status=dead }}</ref> 

Much of ALGOL W's semantics is defined grammatically:<ref name="description"/>
* Identifiers are distinguished by their definition within the current [[Scope (programming)|scope]]. For example, a <code>⟨procedure identifier⟩</code> is an identifier that has been defined by a procedure declaration, a <code>⟨label identifier⟩</code> is an identifier that is being used as a [[goto]] label.
* The [[Type system|types]] of [[Variable (computer science)|variables]] and [[Expression (computer science)|expressions]] are represented by affixes. For example <code>⟨τ function identifier⟩</code> is the syntactic entity for a function that returns a value of type <code>τ</code>, if an identifier has been declared as an integer function in the current scope then that is expanded to <code>⟨integer function identifier⟩</code>.
* Type errors are grammatical errors. For example, <code>⟨integer expression⟩ / ⟨integer expression⟩</code> and <code>⟨real expression⟩ / ⟨real expression⟩</code> are valid but distinct syntactic entities that represent expressions, but <code>⟨real expression⟩ DIV ⟨integer expression⟩</code> (i.e., integer division performed on a floating-point value) is an invalid syntactic entity.