Experience in the design, implementation and use of PL-11, a programming language for the PDP-11

PL-11 is a programming language for the PDP-11 family of computers designed and implemented as part of the OMEGA Project at CERN (the European Organization for Nuclear Research). Its purpose is to provide an effective tool for both physicists and systems programmers to use in building real-time data acquisition systems that are on-line to high-energy physics experiments. It is a fairly typical member of the PL-class of programming languages (44) which are based on the initial design of PL360 (41) (see Table 1). Each of these languages represents a linguistic model of its specific machine architecture, thereby providing a Systems Implementation Language (SIL) that is extremely efficient on its target machine, yet is also highly effective for human programmers to use. The need for such a tool is obvious on all computer systems, but especially on minicomputers, where most applications are in fact “systems programs”. For example, in any data acquisition environment the distinction between “user” and “operating system” largely disappears—the user's prime concern is to handle time-dependent sequences of events involving the manipulation of special I/O devices through direct status checking and data streaming—all functions which are usually buried in the operating system of conventional computing systems. This paper discusses four years of experience with PL-11, especially as this relates to the general topic of SILs on minicomputers.