Editing System programming language (section)

===Mid-level languages===
Mid-level languages "have much of the syntax and facilities of a higher level language, but also provide direct access in the language (as well as providing assembly language) to machine features."<ref name=Sammet /> The earliest of these was [[Executive Systems Problem Oriented Language|ESPOL]] on Burroughs mainframes in about 1960, followed by [[Niklaus Wirth]]'s [[PL360]] (first written on a Burroughs system as a [[cross compiler]]), which had the general syntax of [[ALGOL 60]] but whose statements directly manipulated CPU registers and memory. Other languages in this category include [[MOL-360]] and [[PL/S]].

As an example, a typical PL360 statement is <code>R9 := R8 and R7 shll 8 or R6</code>, signifying that registers 8 and 7 should be and'ed together, the result shifted left 8 bits, the result of that or'ed with the contents of register 6, and the final result placed into register 9.<ref>{{Cite journal |last=Wirth |first=Niklaus |author-link=Niklaus Wirth |title=PL360, A Programming Language for the 360 Computers |journal=Journal of the ACM |date=1968 |volume=15 |issue=1 |pages=37–74|doi=10.1145/321439.321442 }}</ref>