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From: trow@uw-june (Jay Trow)
Newsgroups: net.lang.st80
Subject: Re: Definition of Buzzwords: "Object-Oriented"
Message-ID: <17@uw-june>
Date: Sun, 27-Jan-85 01:30:29 EST
Article-I.D.: uw-june.17
Posted: Sun Jan 27 01:30:29 1985
Date-Received: Mon, 28-Jan-85 07:45:12 EST
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Reply-To: Cornish.sv@Xerox.arpa
Organization: U of Washington Computer Science
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Date: 23 Jan 85 08:58:44 PST (Wednesday)
From: Cornish.SV
Subject: Re: Definition of Buzzwords: "Object-Oriented"

This is not going to be a "rigorous definition".  First, let's realize,
that to say a software system is "object oriented" really means that the
architecture of a software system is "object oriented".

Now just what does the term "architecture of a software system" really
mean?  Any software system has a purpose.  The architecture of a software
system must be devoted to achieving that purpose, just as the architecture
of a building must be devoted to achieving the purpose of that building.

Let's take a historical perspective: what was the first object-oriented
system and what was it's purpose?  I propose a candidate which will come
as no surprise to anyone, SIMULA-67.  Oh yes, SIMULA-67, the father of
SMALLTALK.  Oh yes, SIMULA-67, the frequently cited language in papers
on abstract data types.  Oh yes, SIMULA-67 the language cited as an
inspiration to the designers of the Burroughs 6700 computer, the first
computer with an operating system written in ALGOL.

But just what was the purpose of SIMULA-67, contrasted with the purpose
of ALGOL-60 on which it was based?

SIMULA-67 was designed to for discrete-event simulation applications.
ALGOL-60 was first devised to express mathematical algorithms.  What is
simulation and how is it different from a mathematical algorithm?  Can we
agree that a simulated world consists of "objects"?  What are the
characteristics of such objects, at least relative to the simulation?
Each has a *lifetime* and each has *behavior*.  Each object is "doing
it's own thing" acquiring and releasing resources, even being a resource
itself.  Each object can be identified with a separate process.

Comments?

Jan Cornish

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