IX Basic Concepts in Object-Oriented Programming An Overview of the Beta Language K. Nygaard Rapporteur: G. Pappalardo ... IX. l 7 i-·- The "Newcastle '88. Conference ••• I "The Past, Present and Future of Object Oriented Programming" (probably the "in lecture title" these days) l!!;;;;;;;""""""""""""""""""""............... on Object Oriented Programming ;;;;;;;;;;;;;;;;;;111 © KriSten Nygaard, University of Oslo. Title: "The Past. Present and Future ot oop· The "Newcastle '88 " Conference ••• 1lofu aia it all starf? ... or: etten t~e - ala '3Rnmana - ala ~fkfnga - ala 'iabbage - young ([urtng - early ~fmulatora ana QIA31VQIlU\1lt-era ma @bjert ®rtentea Jrogrnmmfng I l!i&.______ ......... on Object Oriented Programming e Kr1Bten Nyga.&rd. University of Oslo. Title: How did it aJl st&rt? IX.2 The "Newcastle '88 " Conference ••• Object Orgy in Oslo : (Local headline reporting on ECOOP 188) rn.... ___....,; ___ ••• on Object Oriented Programming .....;;;;;;;;iII © Kr1Bten Nygaa,rd, University of Oslo. Title, Object Orgy In Oslol The "Newcastle '88 " Conference ••• Object Oriented Programming ... ... a passingfad? I!!.._....,;_iiiiii........... _ ... on Object Oriented Programming <0 Kr1sten Nygaa.rd., U01verslty of Oslo. Title, • oOP . • P&8S1ng Fod?' IX .3 The "Newcastle '88 " Conference ••• The idea that led to Simula and OOP: To create a languange that made it possible for people V' to comprehend, describe, and communicate about systems V' to analyze existing and proposed systems through computer based models 11.._..... _____ ... on Object Oriented Programming _-aI " Kristen Nygaard. University of Oslo. __ t.hat led to 81mul& an OOP The "Newcastle '88 " CQnference ••• To Describe Is to Understand .~ '----...........-- ... on Object Oriented Programming <C Kr1aten Nygaard, Unlverslty of 0810. _be ~ to Underetan4 IX. 4 The "Newcastle '88 " Conference ••• To Program Is to Understand l!I........ ..............____ ••• on Object Oriented Programming e Krtsten Nygaard, University of Oslo. T1tle: To Program Is to Understand The "Newcastle '88 " Conference ••• I CPU fbe~~.:iAj ········· ·· · ·· ··· · ······· w_ : procedure PI A : real • 1.a3 i Iprocedure 1'; :::BI A I. 1.a3 B:·AJ ......... ..... ; PI· .. I eDdj eDdj ...~. [,».!\I ...................................... eDdj \ ~ Inner bloak IDa\ance B 1 real. 1.83 B:·AJ • ·····t lt;; ... en4 ,.. PlDatanoe l!l;;;;,;................................... _ ••• on Object Oriented Programming Cl Kristen Nyga,ard., University of Oslo. T1tle: Algol Program Exeautll IX .S The "Newcastle '88 " Conference ••• Job shop system oQject IIns~ce I t t + • • Part Operator Machlnel Machlne2 oQject oQject oQject oQject IIns~cel • ~~ t ~ Ilnsta'nce I RJght Left arm arm oQject oQject --t.~ Nesting (static link) l!!;;;;;; .....___ .......... __ ... on Object Oriented Programming Q Kr1sten Nygaard. UDiverslty ot Oslo. T1t1e: 81mula Program Executit The "Newcastle '88 " Conference ••• Each component (object) has its own attributes and action sequence. The action sequences are concurrent in the modelled system (the referent system). In the computer based model concurrency is simulated by alternating sequences. \1;;;;;;;; _______ ••• on Object Oriented Programming <C> Kr1Bt<m Nygaard, University of 0010. _ soquOIlClng·1 IX.6 The "Newcastle '88 " Conference ••• Algol The world considered as a stack of block instances 8jmula The world considered as a nested collection of interactive objects, each object organjzed as a stack l!!;;;;;;;;..,..;................... ___ ••• on Object Oriented Programming <0 Kr1sten Nyga&rd., University of Oslo. Title: AlgollSlmul& Wor ld ViE The "Newcastle '88 " Conference ••• From Mathematical Models to Monte Carlo to General Simulation Models to System Description and Programmjng in General \!l;oa;;,......................................... .. on Object Oriented Programming e Kristen Ny ga&rd., University of Oslo. Title: From Math to !/lonte carlo .... IX. 7 The "Newcastle '88 " Conference •.• SimulaI 1961-64 A system description and simulation language that also was used as a general programming language Simula67 1966-67 A system description and general programming language that also is used as a simulation language La____ .... ....__ ... on Object Oriented Programming C Kristen Nyga.&rd, Univers1ty of 0810. Title: 81mul& Ii81mul& 67 The "Newcastle '88 " Conference ••• From the history of Simula - the Greek Night Club Episode: /I •• a.i'ter the dinner in Wasllington DC, Jim Nlckltas brought KN to a Greek n1gb.t olub, and while they were watc.htng a beautiful belly dancer, Nlckltas proposed this interesting deal: ...... /I "History of Programming Languages", ed. R. Weze1blatt. The version that came very close to final print: /I •• after the dinner in Washington DC, Jim Nlokltas brought KN to a Greek night olub, and while they were was.htng a beautiful belly danoer, Nlokltas proposed this interesting deal: .. .. .. /I I!I... ......................_ .....- ... on Object Oriented Programming C Kr1sten Nyga.&rd, University of Oslo. Title: Greek N1g!l.t Club EpISOde IX .S The "Newcastle '88 " Conference ••• DELTA 1973 -78 a general system description language and not a programming language BETA 1976- a general object oriented programming language and a research project with the objective ofcontributing to new concepts i languages [1..__ ............................. on Object Oriented Programming C Kristen Nygaard, UD.1verslty ot Oslo. TItle: DELTA/BlITA The "Newcastle '88 " Conference ••• The idea that led to Smalltalk and Macintosh: The "Dynabook" To create a book-sized computer that V' contajned a model of all facts relevant to its owner V' a model comprehensible to its owner V' a model used and controlled interactively by its owner ta-_...... ___ ...... _ ... on Object Oriented Programming C Kr18ten Nygaa.rd., University of Oslo. TItle: The !de& tha; led to 8malltalk and Mac1ntoah· IX.9 The "Newcastle '88 " Conference ••• Smallta1k The Dynabook needed: V' Simu1a's classes and subclasses to organize and make comprehensible the facts and models it contained V' Lisp's incrementality to respond immediately to what its user wanted to do V' A new kind of user interface to make the internal organization visible and navigable 11-______ ... on Object Oriented Programming Q Kr1Btsn Nyga&rd, Unlv.ratty of Oslo. Title: BmalIt&Ilt The "Newcastle '88 " Conference ••• Smallta1k What the Dynabook did not need: Multiple action sequences -+ objects with virtual procedures (methods) but not own action sequences -+ no non-virtual procedures Objects within objects -+ only one layer of nesting on Object Oriented Programming _ ..aI 111..----.....- ...... _ the Dynabook d1c1 DOt noed ... Q Kr1Btsn Nyga&rd, Unlv.ratty of Oslo. IX . l O The "Newcastle '88 " Conference ••• ConceptEUerarcbdes Inheritance Classes and Subclasses (Simula 67) Multiple inheritance Flavors (Cannon 1981) Smallta1k, Loops etc. '-----......... ... on Object Oriented Programming ~ e Kr1sten Nygaard, Unlverslty of 0010. Title, concept Hlerr.rah1ee The "Newcastle '88 " Conference ••• -----"""11 Non-Virtual and Virtual Procedures Sirnula 67 Messages = Virtual Procedures + Run Time Binding Smalltalk Generalized Virtual .. Attributes Beta ~ _____... ... on Object Oriented Programming -..:I © Kristen Nygaard. University of Oslo. Title, V!rtu&ls In Slmul&/ Sma1lt&lk/ BETA IX .ll The "Newcastle '88 " Conference .•. Main Application Areas for Object Oriented Programmjng: t/ Simulation From 1965 on t/ General Programming From 1965 on t/ Concurrency, Monitors Ca. 1970 t/ Structured Programming Book appearing in 1973 t/ Abstract DataTypes Much work from ca. 1973 on t/ VSLI Design From the mid-seventies on t/ Workstation Environments, Incremental Computing Smalltalk versions 1972-76-80 t/ Reusable Software Modules Early work from 1967 on, much work from ca.1980 !II... ___iliiiiiliiiiiliiii ..... iiii ••• on Object Oriented Programming C Kr1sten Nyga.ard. Universlty ot Oslo. Title: Mam Appl1catlon Ar~ The "Newcastle '88 " Conference ••• Dimensions in Object Space 1Mo..... __ ............... iiiiiliiiii ••• on Object Oriented Programming C Kristen Nygaard. University of Oslo. __IOnS In O~ect Sp&oo • I 1X.12 The "Newcastle '88 " Conference ••• Dimensions in Object Space - 2 Objects' basic qualities V Substance V Value: Measure ot state properties V Transitions tM.____ ................. ... on Object Oriented Programming C Kristen Nygaard. University of Oslo. __lena In O~""' 8p.,.,.2. B.. le qualltJea The "Newcastle '88 " Conference ••• Hierarchical Organization v Action Hierarchies by stacked objects V Value Hierarchies by categories and subcategories: patterns and subpatterns in BETA V Substance Hierarchies by nested objects in S1mula and BETA V Structure (Concept) Hierarchies by categories and subcategories: classes/subclasses in S1mula/Smalltalk etc., patterns and subpatterns in BETA V Program. Execution Hierarchies (from hardware through operating systems layers to program executions) by the actor/role concept in BETA. rn............................................ ... on Object Oriented Programming © Kr1Bten Nygaard. University of OSlo. Title: mera.rch1cal Org&n1z&t.1I I X.13 The "Newcastle '88 " Conference ••• lopu , ... .. ...................." .................. ibeginrealA; lnnaDoe : procellu:re P, A : real - 1.13 , A:-l.13, proce4u:re PJ begin real B, A :-l.13 B:-A; ......... .....; P; '0' , oOL eII4j eD4; ... ~. eII4j \ 1'».«I n n •• n n • • ••• n •••• n . n •• n. n n n. _blocklDAance " B I real- 1.13 1.1 B:- A; ..... ; P; ; ... end. ~