Editing Mesa (programming language) (section)

{{Use dmy dates|date=June 2016}}
{{Infobox programming language
| name                   = Mesa<ref name="manual">[[James G. Mitchell|Mitchell, James G.]]; Maybury, William; Sweet, Richard (1979): [http://www.bitsavers.org/pdf/xerox/parc/techReports/CSL-79-3_Mesa_Language_Manual_Version_5.0.pdf Mesa Language Manual - version 5.0]" XEROX PARC, Computer Systems Laboratory (CSL), Technical Report CSL-79-3.   Online copy at www.bitsavers.org, accessed on 2019-05-15.</ref>
| designer               = Computer Systems Laboratory (CSL)<!-- or: | designers = -->
| developer              = [[Xerox PARC]] <!-- or: | developers = -->
| released               = {{start date and age|df=yes|1976}}<ref name="releasesspmesa">[http://www.softwarepreservation.org/projects/lang/mesa Mesa], Software Preservation Group</ref>
| latest release version = Mesa 6.0 (Version 41)
| latest release date    = {{start date and age|df=yes|1981|07}}
| typing                 = Strong, static
| influenced by          = [[ALGOL]]
| influenced             = [[Java (programming language)|Java]], [[Modula-2]], [[Cedar (programming language)|Cedar]], [[PostScript]]<ref>{{cite journal |last1=Perry |first1=T.S. |title='PostScript' prints anything: a case history |journal=IEEE Spectrum |date=May 1988 |volume=25 |issue=5 |pages=42–46 |doi=10.1109/6.4550|s2cid=33376390 }}</ref>
}}
'''Mesa'''<ref name="manual" /> is a [[programming language]] developed in the mid 1970s at the [[PARC (company)|Xerox Palo Alto Research Center]] in [[Palo Alto, California]], [[United States]]. The language name was a pun based upon the programming language catchphrases of the time, because Mesa is a [[high-level programming language|"high level" programming language]].

Mesa is an [[ALGOL]]-like language with strong support for [[modularity (programming)|modular programming]]. Every library module has at least two [[source code|source]] files: a ''definitions'' file specifying the library's [[interface (computer science)|interface]] plus one or more ''program'' files specifying the [[implementation]] of the procedures in the interface.<ref>''Mesa Language Manual'', chapter 7. (The ''Manual'' uses the term ''module'' to mean a source file.)</ref> To use a library, a program or higher-level library must "import" the definitions. The Mesa compiler [[Type system#Type checking|type-checks]] all uses of imported entities; this combination of separate compilation with type-checking was unusual at the time.{{citation needed|date=October 2016}}

Mesa introduced several other innovations in language design and implementation, notably in the handling of [[exception (programming)|software exception]]s, [[Thread (computing)|thread]] [[synchronization (computer science)|synchronization]], and [[incremental compilation]].

Mesa was developed on the [[Xerox Alto]], one of the first [[personal computer]]s with a [[graphical user interface]], however, most of the Alto's system software was written in [[BCPL]]. Mesa was the system programming language of the later [[Xerox Star]] workstations, and for the [[GlobalView]] desktop environment.  Xerox PARC later developed [[#Cedar|Cedar]], which was a superset of Mesa.

Mesa and Cedar had a major influence on the design of other important languages, such as [[Modula-2]] and [[Java (programming language)|Java]], and was an important vehicle for the development and dissemination of the fundamentals of [[GUI]]s, networked environments, and the other advances [[Xerox]] contributed to the field of [[computer science]].