UCSD Pascal
Encyclopedia
UCSD Pascal was a Pascal
programming language
system that ran on the UCSD p-System, a portable, highly machine-independent operating system
. UCSD Pascal was first released in 1978. It was developed at the University of California, San Diego
(UCSD).
s as well as campus DEC
PDP-11
minicomputer
s. UCSD p-System (Version IV, supplied by SofTech
) was one of three operating systems (along with PC-DOS
and CP/M-86
) that IBM
offered for its original IBM PC
; but the p-System never sold very well for the IBM PC, mainly because of a lack of applications and because it was more expensive than the other choices. Previously, IBM had offered the UCSD p-System as an option for Displaywriter, an 8086-based dedicated word processing machine (not to be confused with IBM's DisplayWrite
word processing software.) (The Displaywriter's native operating system had been developed completely internally and was not opened for end-user programming.)
Notable extensions to standard Pascal include separately compilable Units and a String type. Both of these extensions influenced the design of the Ada
language.
Some intrinsics were provided to accelerate string processing (e.g. scanning in an array for a particular search pattern); other language extensions were provided to allow the UCSD p-System to be self-compiling and self-hosted
.
UCSD Pascal was based on a p-code machine
architecture. Its contribution to these early virtual machines was to extend p-code away from its roots as a compiler intermediate language
into a full execution environment. The UCSD Pascal p-Machine was optimized for the new small microcomputers with addressing restricted to 16-bit (only 64KB of memory). James Gosling
cites UCSD Pascal as a key influence (along with the Smalltalk
virtual machine) on the design of the Java
virtual machine.
UCSD p-System achieved machine independence by defining a virtual machine
, called the p-Machine (or pseudo-machine, which many users began to call the "Pascal-machine" like the OS—although UCSD documentation always used "pseudo-machine") with its own instruction set
called p-code
(or pseudo-code). Urs Ammann, a student of Niklaus Wirth
, originally presented a p-code in his PhD
thesis, from which the UCSD implementation was derived, the Zurich Pascal-P implementation. The UCSD implementation changed the Zurich implementation to be "byte oriented". The UCSD p-code was optimized for execution of the Pascal programming language. Each hardware platform then only needed a p-code interpreter program written for it to port the entire p-System and all the tools to run on it. Later versions also included additional languages that compiled to the p-code base. For example, TeleSoft (also located in San Diego) offered an early Ada development environment that used p-code and was therefore able to run on a number of hardware platforms including the Motorola 68000
, the System/370
, and the Pascal MicroEngine
.
UCSD p-System shares some concepts with the more current Java platform. Both use a virtual machine to hide operating system and hardware differences, and both use programs written to that virtual machine to provide cross-platform
support. Likewise both systems allow the virtual machine to be used either as the complete operating system
of the target computer or to run in a "box" under another operating system.
The UCSD Pascal compiler was distributed as part of a portable operating system
, the p-System.
, who believed that the number of new computing platforms coming out at the time would make it difficult for new programming languages to gain acceptance. He based UCSD Pascal on the Pascal-P2 release of the portable compiler
from Zurich. He was particularly interested in Pascal
as a language to teach programming. UCSD introduced two features that were important improvements on the original Pascal: variable length strings, and "units" of independently compiled code (an idea included into the then-evolving Ada programming language). Niklaus Wirth
credits the p-System, and UCSD Pascal in particular, with popularizing Pascal. It was not until the release of Turbo Pascal
that UCSD's version started to slip from first place among Pascal users.
The Pascal dialect of UCSD Pascal came from the subset of Pascal implemented in Pascal-P2, which was not designed to be a full implementation of the language, but rather "the minimum subset that would self-compile", to fit its function as a bootstrap kit for Pascal compilers. UCSD added strings from BASIC, and several other implementation dependent features. Although UCSD Pascal later obtained many of the other features of the full Pascal language, the Pascal-P2 subset persisted in other dialects, notably Borland Pascal, which copied much of the UCSD dialect.
Pascal (programming language)
Pascal is an influential imperative and procedural programming language, designed in 1968/9 and published in 1970 by Niklaus Wirth as a small and efficient language intended to encourage good programming practices using structured programming and data structuring.A derivative known as Object Pascal...
programming language
Programming language
A programming language is an artificial language designed to communicate instructions to a machine, particularly a computer. Programming languages can be used to create programs that control the behavior of a machine and/or to express algorithms precisely....
system that ran on the UCSD p-System, a portable, highly machine-independent operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
. UCSD Pascal was first released in 1978. It was developed at the University of California, San Diego
University of California, San Diego
The University of California, San Diego, commonly known as UCSD or UC San Diego, is a public research university located in the La Jolla neighborhood of San Diego, California, United States...
(UCSD).
UCSD Pascal and the p-System
UCSD Pascal was developed at The University of California, San Diego Institute for Information Systems in 1978 to provide students with a common operating system that could run on any of the then available microcomputerMicrocomputer
A microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...
s as well as campus DEC
Digital Equipment Corporation
Digital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
PDP-11
PDP-11
The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...
minicomputer
Minicomputer
A minicomputer is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems and the smallest single-user systems...
s. UCSD p-System (Version IV, supplied by SofTech
SofTech, Inc.
SofTech, Inc., , developer of ProductCenter, the company's PDM/PLM solution. WTC was one of the earliest PDM/PLM providers in the industry, having delivered PLM software products beginning with its first software product CMS in the early 1990s, along with many technology firsts, including the...
) was one of three operating systems (along with PC-DOS
PC-DOS
IBM PC DOS is a DOS system for the IBM Personal Computer and compatibles, manufactured and sold by IBM from the 1980s to the 2000s....
and CP/M-86
CP/M-86
CP/M-86 was a version of the CP/M operating system that Digital Research made for the Intel 8086 and Intel 8088. The commands are those of CP/M-80. Executable files used the relocatable .CMD file format...
) that IBM
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
offered for its original IBM PC
IBM PC
The IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...
; but the p-System never sold very well for the IBM PC, mainly because of a lack of applications and because it was more expensive than the other choices. Previously, IBM had offered the UCSD p-System as an option for Displaywriter, an 8086-based dedicated word processing machine (not to be confused with IBM's DisplayWrite
DisplayWrite
DisplayWrite was a word processor software application that IBM developed and marketed for its line of IBM PCs. Its document files used the RFT or DCA filename extension, both of which were standards on IBM mainframe computers...
word processing software.) (The Displaywriter's native operating system had been developed completely internally and was not opened for end-user programming.)
Notable extensions to standard Pascal include separately compilable Units and a String type. Both of these extensions influenced the design of the Ada
Ada (programming language)
Ada is a structured, statically typed, imperative, wide-spectrum, and object-oriented high-level computer programming language, extended from Pascal and other languages...
language.
Some intrinsics were provided to accelerate string processing (e.g. scanning in an array for a particular search pattern); other language extensions were provided to allow the UCSD p-System to be self-compiling and self-hosted
Self-hosting
The term self-hosting was coined to refer to the use of a computer program as part of the toolchain or operating system that produces new versions of that same program—for example, a compiler that can compile its own source code. Self-hosting software is commonplace on personal computers and larger...
.
UCSD Pascal was based on a p-code machine
P-Code machine
In computer programming, a p-code machine, or portable code machine is a virtual machine designed to execute p-code...
architecture. Its contribution to these early virtual machines was to extend p-code away from its roots as a compiler intermediate language
Intermediate language
In computer science, an intermediate language is the language of an abstract machine designed to aid in the analysis of computer programs. The term comes from their use in compilers, where a compiler first translates the source code of a program into a form more suitable for code-improving...
into a full execution environment. The UCSD Pascal p-Machine was optimized for the new small microcomputers with addressing restricted to 16-bit (only 64KB of memory). James Gosling
James Gosling
James A. Gosling, OC is a computer scientist, best known as the father of the Java programming language.-Education and career:In 1977, Gosling received a B.Sc in Computer Science from the University of Calgary...
cites UCSD Pascal as a key influence (along with the Smalltalk
Smalltalk
Smalltalk is an object-oriented, dynamically typed, reflective programming language. Smalltalk was created as the language to underpin the "new world" of computing exemplified by "human–computer symbiosis." It was designed and created in part for educational use, more so for constructionist...
virtual machine) on the design of the Java
Java (programming language)
Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems' Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities...
virtual machine.
UCSD p-System achieved machine independence by defining a virtual machine
Virtual machine
A virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
, called the p-Machine (or pseudo-machine, which many users began to call the "Pascal-machine" like the OS—although UCSD documentation always used "pseudo-machine") with its own instruction set
Instruction set
An instruction set, or instruction set architecture , is the part of the computer architecture related to programming, including the native data types, instructions, registers, addressing modes, memory architecture, interrupt and exception handling, and external I/O...
called p-code
P-code
P-code can refer to:* Precompiled code, for example Java Byte code, MATLAB .p-files, etc.* p-code machine * Code used in the UCSD p-System...
(or pseudo-code). Urs Ammann, a student of Niklaus Wirth
Niklaus Wirth
Niklaus Emil Wirth is a Swiss computer scientist, best known for designing several programming languages, including Pascal, and for pioneering several classic topics in software engineering. In 1984 he won the Turing Award for developing a sequence of innovative computer languages.-Biography:Wirth...
, originally presented a p-code in his PhD
PHD
PHD may refer to:*Ph.D., a doctorate of philosophy*Ph.D. , a 1980s British group*PHD finger, a protein sequence*PHD Mountain Software, an outdoor clothing and equipment company*PhD Docbook renderer, an XML renderer...
thesis, from which the UCSD implementation was derived, the Zurich Pascal-P implementation. The UCSD implementation changed the Zurich implementation to be "byte oriented". The UCSD p-code was optimized for execution of the Pascal programming language. Each hardware platform then only needed a p-code interpreter program written for it to port the entire p-System and all the tools to run on it. Later versions also included additional languages that compiled to the p-code base. For example, TeleSoft (also located in San Diego) offered an early Ada development environment that used p-code and was therefore able to run on a number of hardware platforms including the Motorola 68000
Motorola 68000
The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
, the System/370
System/370
The IBM System/370 was a model range of IBM mainframes announced on June 30, 1970 as the successors to the System/360 family. The series maintained backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the...
, and the Pascal MicroEngine
Pascal MicroEngine
The Pascal MicroEngine was a series of microcomputer products manufactured by Western Digital from 1979 through the mid 1980s, designed specifically to efficiently run the UCSD p-System...
.
UCSD p-System shares some concepts with the more current Java platform. Both use a virtual machine to hide operating system and hardware differences, and both use programs written to that virtual machine to provide cross-platform
Cross-platform
In computing, cross-platform, or multi-platform, is an attribute conferred to computer software or computing methods and concepts that are implemented and inter-operate on multiple computer platforms...
support. Likewise both systems allow the virtual machine to be used either as the complete operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
of the target computer or to run in a "box" under another operating system.
The UCSD Pascal compiler was distributed as part of a portable operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
, the p-System.
History
UCSD p-System began around 1974 as the idea of UCSD's Kenneth BowlesKenneth Bowles
Dr. Kenneth L "Ken" Bowles is best known for his work in initiating and directing the UCSD Pascal project, when he was a professor of Computer Science at the University of California, San Diego .- Education :Bowles received his PhD under Prof...
, who believed that the number of new computing platforms coming out at the time would make it difficult for new programming languages to gain acceptance. He based UCSD Pascal on the Pascal-P2 release of the portable compiler
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
from Zurich. He was particularly interested in Pascal
Pascal (programming language)
Pascal is an influential imperative and procedural programming language, designed in 1968/9 and published in 1970 by Niklaus Wirth as a small and efficient language intended to encourage good programming practices using structured programming and data structuring.A derivative known as Object Pascal...
as a language to teach programming. UCSD introduced two features that were important improvements on the original Pascal: variable length strings, and "units" of independently compiled code (an idea included into the then-evolving Ada programming language). Niklaus Wirth
Niklaus Wirth
Niklaus Emil Wirth is a Swiss computer scientist, best known for designing several programming languages, including Pascal, and for pioneering several classic topics in software engineering. In 1984 he won the Turing Award for developing a sequence of innovative computer languages.-Biography:Wirth...
credits the p-System, and UCSD Pascal in particular, with popularizing Pascal. It was not until the release of Turbo Pascal
Turbo Pascal
Turbo Pascal is a software development system that includes a compiler and an integrated development environment for the Pascal programming language running on CP/M, CP/M-86, and DOS, developed by Borland under Philippe Kahn's leadership...
that UCSD's version started to slip from first place among Pascal users.
The Pascal dialect of UCSD Pascal came from the subset of Pascal implemented in Pascal-P2, which was not designed to be a full implementation of the language, but rather "the minimum subset that would self-compile", to fit its function as a bootstrap kit for Pascal compilers. UCSD added strings from BASIC, and several other implementation dependent features. Although UCSD Pascal later obtained many of the other features of the full Pascal language, the Pascal-P2 subset persisted in other dialects, notably Borland Pascal, which copied much of the UCSD dialect.
Versions
There were four versions of UCSD p-code engine, each with several revisions of the p-System and UCSD Pascal. A revision of the p-code engine (i.e., the p-Machine) meant a change to the p-code language, and therefore compiled code is not portable between different p-Machine versions. Each revision was represented with a leading Roman Numeral, while operating system revisions were enumerated as the "dot" number following the p-code Roman Numeral. For example, II.3 represented the third revision of the p-System running on the second revision of the p-Machine.- Version I
-
- Original version, never officially distributed outside of the University of California, San DiegoUniversity of California, San DiegoThe University of California, San Diego, commonly known as UCSD or UC San Diego, is a public research university located in the La Jolla neighborhood of San Diego, California, United States...
. However, the Pascal sources for both Versions I.3 and I.5 were freely exchanged between interested users. Specifically, the patch revision I.5a was known to be one of the most stable.- Version II
- Widely distributed, available on many early microcomputerMicrocomputerA microcomputer is a computer with a microprocessor as its central processing unit. They are physically small compared to mainframe and minicomputers...
s. Numerous versions included Apple IIApple IIThe Apple II is an 8-bit home computer, one of the first highly successful mass-produced microcomputer products, designed primarily by Steve Wozniak, manufactured by Apple Computer and introduced in 1977...
, TI 99/4a, DECDigital Equipment CorporationDigital Equipment Corporation was a major American company in the computer industry and a leading vendor of computer systems, software and peripherals from the 1960s to the 1990s...
PDP-11PDP-11The PDP-11 was a series of 16-bit minicomputers sold by Digital Equipment Corporation from 1970 into the 1990s, one of a succession of products in the PDP series. The PDP-11 replaced the PDP-8 in many real-time applications, although both product lines lived in parallel for more than 10 years...
, Zilog Z80Zilog Z80The Zilog Z80 is an 8-bit microprocessor designed by Zilog and sold from July 1976 onwards. It was widely used both in desktop and embedded computer designs as well as for military purposes...
and MOS 6502 based machines, Motorola 68000Motorola 68000The Motorola 68000 is a 16/32-bit CISC microprocessor core designed and marketed by Freescale Semiconductor...
and the IBM PCIBM PCThe IBM Personal Computer, commonly known as the IBM PC, is the original version and progenitor of the IBM PC compatible hardware platform. It is IBM model number 5150, and was introduced on August 12, 1981...
(Version II on the PC was restricted to one 64K code segmentCode segmentIn computing, a code segment, also known as a text segment or simply as text, is one of the sections of a program in an object file or in memory, which contains executable instructions....
and one 64K stack/heap data segmentData segmentA data segment is a portion of virtual address space of a program, which contains the global variables and static variables that are initialized by the programmer...
; Version IV removed the code segment limit but cost a lot more). - Project members from this era include
- Dr Kenneth L BowlesKenneth BowlesDr. Kenneth L "Ken" Bowles is best known for his work in initiating and directing the UCSD Pascal project, when he was a professor of Computer Science at the University of California, San Diego .- Education :Bowles received his PhD under Prof...
- Mark AllenMark Allen (software developer)Mark Allen is a software engineer, game programmer and game designer. As a student at the University of California, San Diego, Allen used UCSD Pascal to develop a 6502 interpreter for the Pascal language in 1978, along with Richard Gleaves...
- Richard Gleaves
- Richard Kaufmann
- Pete Lawrence
- Joel McCormackJoel McCormackJoel McCormack is the designer of the NCR Corporation version of the p-code machine which is a kind of Stack machine popular in the 1970s as the preferred way to implement new computing architectures and languages such as Pascal and BCPL...
- Mark Overgaard
- Keith Shillington
- Roger Sumner
- John Van Zandt
- Version III
- Dr Kenneth L Bowles
- Custom version written for Western DigitalWestern DigitalWestern Digital Corporation is one of the largest computer hard disk drive manufacturers in the world. It has a long history in the electronics industry as an integrated circuit maker and a storage products company. Western Digital was founded on April 23, 1970 by Alvin B...
to run on their Pascal MicroEnginePascal MicroEngineThe Pascal MicroEngine was a series of microcomputer products manufactured by Western Digital from 1979 through the mid 1980s, designed specifically to efficiently run the UCSD p-System...
microcomputer. Included support for parallel processes for the first time.- Version IV
- Commercial version, developed and sold by SofTech. Based on Version II; did not include changes from Version III. Did not sell well due to combination of their pricing structure, performance problems due to p-code interpreter, and competition with native operating systems (on top of which it often ran). After SofTech dropped the product, it was picked up by Pecan Systems, a relatively small company formed of p-System users and fans. Sales revived somewhat, due mostly to Pecan's reasonable pricing structure, but the p-System and UCSD Pascal gradually lost the market to native operating systems and compilers.
- Original version, never officially distributed outside of the University of California, San Diego
External links
, UCSD has released portions of the p-System written before June 1, 1979 for non-commercial use. (Note: Webpage resizes browser window.)- UCSD Pascal Reunion Symposium held October 22, 2004
- ucsd-psystem-os, cross-compilable source code for the UCSD p-System version II.0
- ucsd-psystem-vm, a portable virtual machine for UCSD p-System p-code
- A reconstruction of the UCSD Pascal System II.0 User Manual
- UCSD P-System Museum within the Jefferson Computer Museum
- UCSD P-System at Pascal for Small Machines
- UCSD Pascal Yahoo Group
- Gosling's ACM Interview, see page 2.