PL/M

The PL/M programming language (an acronym of Programming Language for Microcomputers^[2][3]) is a high-level language conceived and developed by Gary Kildall^[2][3][4][1] in 1973^[2][3] for ^[2][3] at Intel for its microprocessors.

Overview[]

The language incorporated ideas from PL/I, ALGOL^{[citation needed]} and XPL,^[2][3] and had an integrated macro processor. As a graduate of the University of Washington Kildall had used their Burroughs B5500 computer,^[5] and as such was aware of the potential of high-level languages such as ESPOL for systems programming.

Unlike other contemporary languages such as Pascal, C or BASIC, PL/M had no standard input or output routines. It included features targeted at the low-level hardware specific to the target microprocessors, and as such, it could support direct access to any location in memory, I/O ports and the processor interrupt flags in a very efficient manner. PL/M was the first higher level programming language for microprocessor-based computers and was the original implementation language for those parts of the CP/M operating system which were not written in assembler. Many Intel and Zilog Z80-based embedded systems were programmed in PL/M during the 1970s and 1980s. For instance, the firmware of the Service Processor component of CISC IBM AS/400 was written in PL/M.

The original PL/M compiler targeted the Intel 8008. An updated version (PL/M-80) generated code for the 8080 processor, which would also run on the newer Intel 8085 as well as on the Zilog Z80 family (as it is backward-compatible with the 8080). Later followed compilers for the Intel 8048 and Intel 8051-microcontroller family (PL/M-51) as well as for the 8086 (8088) (PL/M-86), 80186 (80188) and subsequent 8086-based processors, including the advanced 80286 and the 32-bit 80386. There were also PL/M compilers developed for later microcontrollers, such as the Intel 8061 and 8096 / MCS-96 architecture family (PL/M-96).^[6]

While some PL/M compilers were "native", meaning that they ran on systems using that same microprocessor, e.g. for the Intel ISIS operating system, there were also cross compilers, for instance , which ran on other operating environments such as Digital Research CP/M, Microsoft's DOS, and Digital Equipment Corporation's VAX/VMS.

PL/M is no longer supported by Intel, but aftermarket tools like PL/M-to-C source-code translators exist.

PL/M sample code[]

FIND: PROCEDURE(PA,PB) BYTE;
    DECLARE (PA,PB) BYTE;
    /* FIND THE STRING IN SCRATCH STARTING AT PA AND ENDING AT PB */
    DECLARE J ADDRESS,
        (K, MATCH) BYTE;
    J = BACK ;
    MATCH = FALSE;
        DO WHILE NOT MATCH AND (MAXM > J);
        LAST,J = J + 1; /* START SCAN AT J */
        K = PA ; /* ATTEMPT STRING MATCH AT K */
            DO WHILE SCRATCH(K) = MEMORY(LAST) AND
                NOT (MATCH := K = PB);
            /* MATCHED ONE MORE CHARACTER */
            K = K + 1; LAST = LAST + 1;
            END;
        END;
    IF MATCH THEN /* MOVE STORAGE */
        DO; LAST = LAST - 1; CALL MOVER;
        END;
    RETURN MATCH;
    END FIND;

References[]

Further reading[]

• PL/M-80 Programming Manual (PDF). Intel Corporation. January 1980 [1976]. Doc # 98-268B. Archived (PDF) from the original on 2019-12-21. Retrieved 2020-01-29.
• MCS-8 Guide to PL/M Programming (PDF). Intel Corporation. September 1973. Archived (PDF) from the original on 2019-12-21. Retrieved 2020-02-02.
• PL/M 386 Programmer's Guide (PDF). RadiSys Corporation. December 1999. Archived (PDF) from the original on 2006-08-14. Retrieved 2020-01-29. (NB. Includes entire syntax of PL/M in BNF notation.)
• McCracken, Daniel D. (1978). A Guide to PL/M Programming for Microcomputer Applications. Pearson / Addison-Wesley.

This article is based on material taken from the Free On-line Dictionary of Computing prior to 1 November 2008 and incorporated under the "relicensing" terms of the GFDL, version 1.3 or later.