|Developer||Gary Kildall at Digital Research|
|ALGOL, PL/I, XPL|
The PL/M programming language (an acronym of Programming Language for Microcomputers) is a high-level language conceived and developed by Gary Kildall in 1973 for Hank Smith at Intel for its microprocessors.
The language incorporated ideas from PL/I, ALGOL and XPL, and had an integrated macro processor. As a graduate of the University of Washington Kildall had used their B5500 computer, 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 AS/400 was written in PL/M.
The original PL/M compiler targeted the Intel 8008. An updated version 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 as well as for the 8086 (8088), 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.
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 PLMX, which ran on other operating environments such as CP/M, Microsoft's DOS, and Digital Equipment Corporation's VAX/VMS.
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;
- Swaine, Michael (2001-06-22). "Gary Kildall and Collegial Entrepreneurship". Dr. Dobb's Journal. Retrieved 2006-11-20.
- Shustek, Len (2016-08-02). "In His Own Words: Gary Kildall". Remarkable People. Computer History Museum.
- Kildall, Gary Arlen (2016-08-02) . Kildall, Scott; Kildall, Kristin (eds.). "Computer Connections: People, Places, and Events in the Evolution of the Personal Computer Industry" (Manuscript, part 1). Kildall Family. Retrieved 2016-11-17.
- ISIS, Intellec, PL/M and Intel
- Intel Corporation (1976). PL/M-80 Programming Manual. Doc # 98-268B.
- McCracken, Daniel D. (1978). A Guide to PL/M Programming for Microcomputer Applications. Pearson Addison-Wesley.
- PL/M 386 Programmer’s Guide (PDF) – RadiSys Corporation, December 1999. Includes entire syntax of PL/M in BNF notation. Also available on Archive.org.
- PL/M-80 Programming Manual – Intel Corporation (On Bitsavers.org).
- MCS-8 Guide to PL/M Programming – Intel Corporation (On Bitsavers.org).