Editing Mesa (programming language) (section)

==History==
Mesa was originally designed<!--Dates??? Names???--> in the Computer Systems Laboratory (CSL), a branch of the Xerox Palo Alto Research Center, for the [[Xerox Alto|Alto]], an experimental micro-coded workstation.  Initially, its spread was confined to PARC and a few universities to which Xerox had donated some Altos.

Mesa was later adopted as the systems programming language for Xerox's commercial workstations such as the [[Xerox Star|Xerox 8010 (Xerox Star, Dandelion)]] and [[Xerox Daybreak|Xerox 6085 (Daybreak)]], in particular for the [[Pilot (operating system)|Pilot operating system]].

A secondary development environment, called the [[Xerox Development Environment]] (XDE) allowed developers to debug both the operating system Pilot as well as ViewPoint GUI applications using a world swap mechanism. This allowed the entire "state" of the world to be swapped out, and allowed low-level system crashes which paralyzed the whole system to be debugged. This technique did not scale very well to large application images (several megabytes), and so the Pilot/Mesa world in later releases moved away from the world swap view when the micro-coded machines were phased out in favor of SPARC workstations and Intel PCs running a Mesa PrincOps emulator for the basic hardware instruction set.

Mesa was compiled into a stack-machine language, purportedly with the highest code density ever achieved (roughly 4 bytes per high-level language statement).  This was touted in a 1981 paper where implementors from the Xerox Systems Development Department (then, the development arm of PARC), tuned up the instruction set and published a paper on the resultant code density.<ref>{{citation |date=March 1982 |first1=Richard |last1=Sweet |first2=James |last2=Sandman |title=Proceedings of the first international symposium on Architectural support for programming languages and operating systems - ASPLOS-I |chapter=Empirical analysis of the mesa instruction set |pages=158–166 |doi=10.1145/800050.801839 |isbn=0897910664 |s2cid=1353842 |doi-access=free }}</ref>

Mesa was taught via the Mesa Programming Course that took people through the wide range of technology Xerox had available at the time and ended with the programmer writing a "[[hack (technology slang)|hack]]", a workable program designed to be useful. An actual example of such a hack is the BWSMagnifier, which was written in 1988 and allowed people to magnify sections of the workstation screen as defined by a resizable window and a changeable magnification factor.  Trained Mesa programmers from Xerox were well versed in the fundamental of GUIs, networking, exceptions, and multi-threaded programming, almost a decade before they became standard tools of the trade.

Within Xerox, Mesa was eventually superseded by the [[#Cedar|Cedar]] programming language. Many Mesa programmers and developers left Xerox in 1985; some of them went to [[DEC Systems Research Center]] where they used their experience with Mesa in the design of [[Modula-2+]], and later of [[Modula-3]].