Pascal News

Articles
Abstract
The Performance of Three CP/M-Based Pascal Translators
Mark Scott Johnson and Thomas O. Sidebottom
106 Mission Drive
Palo Alto. California 94303
1981 October
The translation-time .md run-time performance of three CP/M-based
Pascal translators - Sorcim's Pascal/M. MT MicroSYSTEMS' Pascal/MT+, and
Ithaca InterSystems' Pascal/Z - are compared. Using a benchmark of eight
programs on a 4MHz Z80-based microprocessor. we find that Pascal/M excels
in translation time and that Pascal/Z excels in run time. Pascal/MT+'s
translation time approaches that of Pascal/M for long programs. Several
translator limitations are also illustrated by the benchmark.
Introduction
We recently had the opportunity to use and evaluate four
mlcropro .essor-based Pascal translators. We are reporting here the results of
one asped of this evaluation (namely. performance) for three of them.
The performance of a piece of software. such as a programming language
translator. is measured in terms of the amount of resources required by the
software to produce some useful result. The primary resource we are
interested In is time. We measured both the time required to translate a
source program into a machine-executable form and the time required to
execute the translated program. The former is termed translation time and
the latter run time (or execution time).
The three Pascal translators we evaluated are Sorcim's Pascal/M.
MT MicroSYSTEMS' Pucal/MT+. and Ithaca InterSystems' Pascal/Z. All three
run under Digital Research's CP/M operating system. We also evaluated a
fourth translator. the UCSD Pascal system. which runs under its own
operating system. We have excluded UCSD Pascal from our report because we
do not feel a fair comparison of translator performance can be made across
operating systems. Separating the performance attributable to the operating
system from that attributable to the translator is a difficult task. Other
translators beside these three run under CP/M. however. We limited the
study to translators that accept essentially the full Pascal programming
language and that are widely accessible to the general microcomputing public.
Not-for­
Copyright c 1981, Mark Scott Johnson and Thomas O. Sidebottom.
profit reproduction is permitted; all other rights are reserved.
Thus we eliminate from consideration several "tiny" Pascal translators. among
others.
Translators
To better understand the behavior of the three Pascal translators and to
better appreciate the performance results. we begin with a brief introduction
to translator construction. We use translator in the generic sense - any
software system that accepts as input a program in one language (the source
language) and that produces as output a functionally equivalent program
written in another language (the object language). If the source language is
a high-level language such as Pascal and the object language is a low-level
language such as assembly language or machine language. then the translator
is called a compiler. If both the source and the object languages are lowlevel.
then the translator is called an assembler. If the object language is
not the machine language of some real machine. it becomes necessary to
execute the object code with an interpreter. which simulates the object
language on a real computer.
Compilers that translate source programs directly into object programs
are called one-pass compilers. Sometimes compilers are written to perform
one or more intermediate transformations between source and object; these are
called multi-pass compilers. Multi-pass compilers generally take longer than
one-pass compilers. but they often require ·Iess 'llain memory, compile longer
source programs, provide more complete diagnostics. and generate better
object code. To conserve main memory (and again to increase the size of
source programs that can be translated), multi-pass compilers often write out
their intermediate transformations to temporary disk files.
We used version 3.19 of the Pascal/M translator. It is patterned after
the UCSD Pascal system. comprising two components: a compiler that
translates a Pascal source program into P-code - object code for a fictitious.
Pascal-like P-machine - and an interpreter for the P-machine. It is a onepass
compiler written in Pascal. For short and moderately-sized programs the
compiler uses no memory overlays. but long programs require swapping from
the disk of segments of the compiler. It runs in 56K of main memory and
requires no temporary files. The output from the compiler is a file containing
P-code instructions, which is input to the p.-machine interpreter. For
compactness and efficiency. the interpreter is written in the assembly
language of the host computer (a Zilog Z80, in our case).
We used version 5.2 of the Pascal/MT+ translator. It is a true compiler
that generates object code for any of several microprocessors. including the
Z80. It is a three-pass compiler written in Pascal: the first pass converts a
source program into a sequence of logically related characters called tokens.
the second pass builds a symbol table. and the third pass generates object
code and places it in a Microsoft-format. relocatable object file. The compiler
runs in 56K of main memory. using five memory overlays. and it uses one
temporary file for the tokens.
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