The PL/M programming language (an acronym of ''Programming Language for Microcomputers'') is a high-level

language Language is a structured system of communication. The structure of a language is its grammar and the free components are its vocabulary. Languages are the primary means by which humans communicate, and may be conveyed through a variety of ...

conceived and developed by

Gary Kildall Gary Arlen Kildall (; May 19, 1942 – July 11, 1994) was an American computer scientist and microcomputer entrepreneur. During the 1970s, Kildall created the CP/M operating system among other operating systems and programming tools, an ...

in 1973 for Hank Smith at

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 ser ...

for its

microprocessors A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...

Overview

The language incorporated ideas from

PL/I PL/I (Programming Language One, pronounced and sometimes written PL/1) is a procedural, imperative computer programming language developed and published by IBM. It is designed for scientific, engineering, business and system programming. I ...

ALGOL ALGOL (; short for "Algorithmic Language") is a family of imperative computer programming languages originally developed in 1958. ALGOL heavily influenced many other languages and was the standard method for algorithm description used by the ...

and XPL, and had an integrated

macro processor A general-purpose macro processor or general purpose preprocessor is a macro processor that is not tied to or integrated with a particular language or piece of software. A macro processor is a program that copies a stream of text from one place ...

. As a graduate of the

University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seatt ...

Kildall had used their Burroughs 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 Pascal, Pascal's or PASCAL may refer to: People and fictional characters * Pascal (given name), including a list of people with the name * Pascal (surname), including a list of people and fictional characters with the name ** Blaise Pascal, Frenc ...

, C or

BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...

, 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 CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initi ...

operating system which were not written in assembler. Many Intel and

Zilog Z80 The Z80 is an 8-bit microprocessor introduced by Zilog as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his 11 employees starting in early 1975. The first working samples were ...

-based

embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded ...

s were programmed in PL/M during the 1970s and 1980s. For instance, the

firmware In computing, firmware is a specific class of computer software that provides the low-level control for a device's specific hardware. Firmware, such as the BIOS of a personal computer, may contain basic functions of a device, and may provide h ...

of the Service Processor component of CISC IBM AS/400 was written in PL/M. The original PL/M

compiler In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs tha ...

targeted the

Intel 8008 The Intel 8008 ("''eight-thousand-eight''" or "''eighty-oh-eight''") is an early byte-oriented microprocessor designed by Computer Terminal Corporation (CTC), implemented and manufactured by Intel, and introduced in April 1972. It is an 8-bit CP ...

. An updated version (PL/M-80) generated code for the

8080 The Intel 8080 (''"eighty-eighty"'') is the second 8-bit microprocessor designed and manufactured by Intel. It first appeared in April 1974 and is an extended and enhanced variant of the earlier 8008 design, although without binary compatibil ...

processor, which would also run on the newer

Intel 8085 The Intel 8085 ("''eighty-eighty-five''") is an 8-bit microprocessor produced by Intel and introduced in March 1976. It is software-binary compatible with the more-famous Intel 8080 with only two minor instructions added to support its added in ...

as well as on the Zilog Z80 family (as it is

backward-compatible Backward compatibility (sometimes known as backwards compatibility) is a property of an operating system, product, or technology that allows for interoperability with an older legacy system, or with input designed for such a system, especially in ...

with the 8080). Later followed compilers for the

Intel 8048 The MCS-48 microcontroller series, Intel's first microcontroller, was originally released in 1976. Its first members were 8048, 8035 and 8748. The 8048 is probably the most prominent member of the family. Initially, this family was produced ...

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 The Intel 80286 (also marketed as the iAPX 286 and often called Intel 286) is a 16-bit microprocessor that was introduced on February 1, 1982. It was the first 8086-based CPU with separate, non- multiplexed address and data buses and also the ...

and the 32-bit

80386 The Intel 386, originally released as 80386 and later renamed i386, is a 32-bit microprocessor introduced in 1985. The first versions had 275,000 transistors Intel 8061 The Intel 8061 microcontroller is most notable for its use in the Ford EEC-IV automotive engine control unit. A close relative of the 8096, the Intel 8061 is second-sourced by Toshiba (under the model number 6127 and 6126) and Motorola (now Free ...

and 8096 / MCS-96 architecture family (PL/M-96). While some PL/M compilers were "native", meaning that they ran on systems using that same microprocessor, e.g. for the Intel

ISIS Isis (; ''Ēse''; ; Meroitic: ''Wos'' 'a''or ''Wusa''; Phoenician: 𐤀𐤎, romanized: ʾs) was a major goddess in ancient Egyptian religion whose worship spread throughout the Greco-Roman world. Isis was first mentioned in the Old Kin ...

operating system, there were also

cross compiler A cross compiler is a compiler capable of creating executable code for a platform other than the one on which the compiler is running. For example, a compiler that runs on a PC but generates code that runs on an Android smartphone is a cross c ...

s, for instance PLMX, which ran on other operating environments such as

Digital Research Digital Research, Inc. (DR or DRI) was a company created by Gary Kildall to market and develop his CP/M operating system and related 8-bit, 16-bit and 32-bit systems like MP/M, Concurrent DOS, FlexOS, Multiuser DOS, DOS Plus, DR DOS and ...

CP/M,

Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washi ...

DOS DOS is shorthand for the MS-DOS and IBM PC DOS family of operating systems. DOS may also refer to: Computing * Data over signalling (DoS), multiplexing data onto a signalling channel * Denial-of-service attack (DoS), an attack on a communicat ...

, and

Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president un ...

VAX/VMS OpenVMS, often referred to as just VMS, is a multi-user, multiprocessing and virtual memory-based operating system. It is designed to support time-sharing, batch processing, transaction processing and workstation applications. Customers using Ope ...

. 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;

Overview

PL/M sample code

References

Further reading