XPL
Encyclopedia
XPL is a dialect of the PL/I
programming language
, developed in 1967, used for the development of compiler
s for computer languages. It was designed and implemented by a team with William McKeeman, James J. Horning
, and David B. Wortman at Stanford University
and the University of California, Santa Cruz
. It was first announced at the 1968 Fall Joint Computer Conference in San Francisco, California
.
It is the name of both the programming language and the compiler generator system (or TWS: translator writing system
) based on the language.
, in designing PL/I, had largely abandoned the FORTRAN
-flavored language constructs in favor of forms more like ALGOL 60
had in it, so the authors of XPL decided to base XPL on PL/I. XPL was a small language whereas PL/I was not. A significant language feature of XPL was the efficient garbage-collecting of strings, provided by an external subroutine which must be included with each XPL program.
XPL featured a relatively simple bottom-up compiler
system dubbed MSP (mixed strategy precedence) by its authors. It was bootstrapped
through Burroughs Algol
onto the IBM System/360 computer. XCOM, the run-time monitor and program loader, was designed for the extant 2311 disk subsystem and it was efficient on that disk. It was about 50-percent efficient on the later 2314 disks, and very inefficient on the still later 3330 and 3350 disks. The compiler was distributed through the IBM SHARE
users organization.
Subsequent implementations of XPL featured an SLR(1) parser. Subsequent implementations of XCOM featured support for many more disk types, and very efficient utilization of disk space on every supported disk type.
PL/I
PL/I is a procedural, imperative computer programming language designed for scientific, engineering, business and systems programming applications...
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....
, developed in 1967, used for the development of compiler
Compiler
A compiler is a computer program that transforms source code written in a programming language into another computer language...
s for computer languages. It was designed and implemented by a team with William McKeeman, James J. Horning
Jim Horning
James J. "Jim" Horning is an American computer scientist and ACM Fellow.Jim Horning received a PhD in computer science from Stanford University in 1969 for a thesis entitled A Study of Grammatical Inference. He was a founding member, and later Chairman, of the Computer Systems Research Group at the...
, and David B. Wortman at Stanford University
Stanford University
The Leland Stanford Junior University, commonly referred to as Stanford University or Stanford, is a private research university on an campus located near Palo Alto, California. It is situated in the northwestern Santa Clara Valley on the San Francisco Peninsula, approximately northwest of San...
and the University of California, Santa Cruz
University of California, Santa Cruz
The University of California, Santa Cruz, also known as UC Santa Cruz or UCSC, is a public, collegiate university; one of ten campuses in the University of California...
. It was first announced at the 1968 Fall Joint Computer Conference in San Francisco, California
San Francisco, California
San Francisco , officially the City and County of San Francisco, is the financial, cultural, and transportation center of the San Francisco Bay Area, a region of 7.15 million people which includes San Jose and Oakland...
.
It is the name of both the programming language and the compiler generator system (or TWS: translator writing system
Translator (computing)
A Translator is a computer program that translates one programming language instruction into anotherprogramming language instruction without the loss of original meaning. OR, the translator will translate X...
) based on the language.
Overview
XPL was designed just as PL/I was introduced. IBMIBM
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...
, in designing PL/I, had largely abandoned the FORTRAN
Fortran
Fortran is a general-purpose, procedural, imperative programming language that is especially suited to numeric computation and scientific computing...
-flavored language constructs in favor of forms more like ALGOL 60
ALGOL
ALGOL is a family of imperative computer programming languages originally developed in the mid 1950s which greatly influenced many other languages and became the de facto way algorithms were described in textbooks and academic works for almost the next 30 years...
had in it, so the authors of XPL decided to base XPL on PL/I. XPL was a small language whereas PL/I was not. A significant language feature of XPL was the efficient garbage-collecting of strings, provided by an external subroutine which must be included with each XPL program.
XPL featured a relatively simple bottom-up compiler
Bottom-up parsing
Bottom-up parsing is a strategy for analyzing unknown information that attempts to identify the most fundamental units first, and then to infer higher-order structures from them...
system dubbed MSP (mixed strategy precedence) by its authors. It was bootstrapped
Bootstrapping (compilers)
In computer science, bootstrapping is the process of writing a compiler in the target programming language which it is intended to compile...
through Burroughs Algol
ALGOL
ALGOL is a family of imperative computer programming languages originally developed in the mid 1950s which greatly influenced many other languages and became the de facto way algorithms were described in textbooks and academic works for almost the next 30 years...
onto the IBM System/360 computer. XCOM, the run-time monitor and program loader, was designed for the extant 2311 disk subsystem and it was efficient on that disk. It was about 50-percent efficient on the later 2314 disks, and very inefficient on the still later 3330 and 3350 disks. The compiler was distributed through the IBM SHARE
SHARE (computing)
SHARE Inc. is a volunteer-run user group for IBM mainframe computers that was founded in 1955 by Los Angeles-area IBM 701 users. It evolved into a forum for exchanging technical information about programming languages, operating systems, database systems, and user experiences for enterprise users...
users organization.
Subsequent implementations of XPL featured an SLR(1) parser. Subsequent implementations of XCOM featured support for many more disk types, and very efficient utilization of disk space on every supported disk type.