2. Władysław M. Turski 1

3. 2 It Was Fun While It Lasted

4. Władysław M. Turski 3 It Wasn't Much Fun 1959, Moscow (USSR), M.Sc. Thesis I was a computer

5. Władysław M. Turski 4 It Was Fun 1960, Manchester (UK), Mercury When love prevails Logic fails So the computer Was made neuter

6. Władysław M. Turski 5 It Was Fun Computing meteor stream orbits

7. Władysław M. Turski 6 It Was Fun Running simulations of meteor swarms evolution

8. Władysław M. Turski 7 It Was a Mistake I thought the computer was for computing (Just as Aristotle thought brain was for cooling blood)

9. Władysław M. Turski 8 But it took me long time to see the light First I thought computers were too difficult to program

10. Władysław M. Turski 9 But it took me long time to see the light So I wrote compilers KLIPA, ALGOL-60

11. Władysław M. Turski 10 But it took me long time to see the light Then I thought running programs on computers was too messy

12. Władysław M. Turski 11 But it took me long time to see the light So I wrote an operating system SODA

13. Władysław M. Turski 12 But it took me long time to see the light Then I thought something was amiss with the data

14. Władysław M. Turski 13 But it took me long time to see the light So I played with data structures

15. Władysław M. Turski 14 And Ive sinned For five long years I worked in the industry. Directing the transfer of OS/360 to Polish-made RIAD computers.

16. Władysław M. Turski 15 Much later (1983, Dublin) Responding to an invited paper I said: Fred Brooks is a hard act to follow: I know, Ive lifted the OS/360 !

17. Władysław M. Turski 16 Then I thought I saw the light Computer is for executing programs !

18. Władysław M. Turski 17 Programming methodology Structured programming (programming structures) GOTO considered harmful

19. Władysław M. Turski 18 Programming methodology Step-wise refinement Correctness

20. Władysław M. Turski 19 Programming methodology Correctness, yes but what does it mean? With respect to...

21. Władysław M. Turski 20 Programming methodology Correctness wrt formal specification - faultily faultless - clear, but useless

22. Władysław M. Turski 21 Programming methodology Specs RealityProgram Correctness? Ill-defined relationship

23. Władysław M. Turski 22 Programming methodology Theory Model Satisfaction Well-defined r elationship

24. Władysław M. Turski 23 I was sure I saw the light It all reduces to theories. A good theory leads to good programs and satisfied customers. A poor theory hinders construction of good programs and makes customers weep.

25. Władysław M. Turski 24 I was sure I saw the light Build theories of small domains, make program-models for them, then combine theories and programs shall jell together!

26. Władysław M. Turski 25 I was sure I saw the light But it aint necessarily so! combining theories is difficult (and not always possible) combining implementations is (nearly always) messy and often dangerous

27. Władysław M. Turski 26 I was sure I saw the light I thought that perhaps combinig little actions into larger systems should be done entirely without any notion of time, i.e even without any predetermined notion of follows.

28. Władysław M. Turski 27 I was sure I saw the light Thus the concept of doubly guarded command was born and (partially) explored

29. Władysław M. Turski 28 But while I followed the light The world was changing became the soup du jour

30. Władysław M. Turski 29 In the new brave world Computers, becoming ever more numerous (and physically smaller), disappear behind services they provide.

31. Władysław M. Turski 30 In the new brave world Computation has to be correct. Service has to be dependable.

32. Władysław M. Turski 31 In the new brave world The mathematical, strict criterion of correctness is being replaced by a behavioural, loose criterion of dependability.

33. Władysław M. Turski 32 In the new brave world All actors (people, machines and systems thereof) occasionally malfunction. This is not only accepted, but also expected.

34. Władysław M. Turski 33 In the new brave world No-one really complains that Windows is prone to crash, only that it crashes at an inopportune moment.

35. Władysław M. Turski 34 In the new brave world Like no-one complains that tires occasionally go flat, only that it happens when we are particularly short of time.

36. Władysław M. Turski 35 In the new brave world No-one is to blame and the guilt is subtly shifted to the user: If I only didnt drive there, if I only didnt press these two keys together! Or was it three?

37. Władysław M. Turski 36 In the new brave world Every hour more users than babies are born. Each user soon becomes an expert at their specific fingering. Such an expertise quickly becomes an article of faith and an academic discipline.

38. Władysław M. Turski 37 In the new brave world Particular fingerings turned articles of faith cum academic disciplines are invested.

39. Władysław M. Turski 38 An aside, from Websters: invest - to array in the symbols of office and honor - to furnish with power or authority - to surround with troops or ships so as to prevent escape or entry - to commit money in order to earn a financial return

40. Władysław M. Turski 39 In the new brave world In the ecumenical primordial ocean of Internet, growth is primarily by accretion of external grime. Reason is yet to be born: while no-one convinces, many try to catch.

41. Władysław M. Turski 40 In the new brave world Correctness, rigour, mathematics of computing is pushed into an ever smaller and darker corner labelled special concerns.

42. Władysław M. Turski 41 I have the feeling that Having witnessed the birth of computing science, I am witnessing its demise.

43. Władysław M. Turski 42 While it lasted It certainly was fun!

44. Władysław M. Turski 43 ?