Software. Is

Transcription

1 Software Is

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4 Any program is a model of a model within a theory of a model of an abstraction of some portion of the world or of some universe of discourse. Meir M Lehman "Programs, Life Cycles, and Laws of Software Evolution"

5 The purpose of abstraction is not to be vague, but to create a new semantic level in which one can be absolutely precise. Edsger W Dijkstra

6 It's just semantics.

7 It's just meaning.

8 It's just details.

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10 Details count. Peter Weinberger

11 Geeks are people who love something so much that all the details matter. Marissa Mayer

12 We're talking about a very specific mindset that is crucial when it comes to the act of creating. Will Gompertz Think Like an Artist

13 It is an attitude that can be encapsulated in a simple but demanding rule: always think both big picture and fine detail. Will Gompertz Think Like an Artist

14 software

15 software architecture

16 code

17 implementation

18 implementation details

19 design details

20 design decisions

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22 Architecture represents the significant design decisions that shape a system, where significant is measured by cost of change. Grady Booch

23 Architecture is a hypothesis, that needs to be proven by implementation and measurement. Tom Gilb

24 We propose [...] that one begins with a list of difficult design decisions or design decisions which are likely to change. Each module is then designed to hide such a decision from the others. David L Parnas On the Criteria to Be Used in Decomposing Systems into Modules

25 Programming is a design activity. Jack W Reeves What Is Software Design?

26 Coding actually makes sense more often than believed. Often the process of rendering the design in code will reveal oversights and the need for additional design effort. The earlier this occurs, the better the design will be. Jack W Reeves What Is Software Design?

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28 If a plot works out exactly as you first planned, you're not working loosely enough to give room to your imagination and instincts.

29 / WordFriday

30 pantser, noun Writer who writes by the seat of their pants. In contrast to a plotter, a pantser doesn't work to (or have) an outline.

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33 16-bit

34 32-bit

35 64-bit

36 <windows.h>

37 LLP64

38 LP64

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40 Hamlet: To be, or not to be, that is the question.

41 Ophelia: 'Tis in my memory locked, and you yourself shall keep the key of it.

42 Hamlet: Yea, from the table of my memory I'll wipe away all trivial fond records.

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44 Unshared mutable data needs no synchronisation Unshared Mutable Shared mutable data needs synchronisation Shared Unshared immutable data needs no synchronisation Immutable Shared immutable data needs no synchronisation

45 Mutable The Synchronisation Quadrant Unshared mutable data needs no synchronisation Unshared Shared mutable data needs synchronisation Shared Unshared immutable data needs no synchronisation Immutable Shared immutable data needs no synchronisation

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47 All computers wait at the same speed

48 Savings in time feel like simplicity

49 ... premature optimization is the root of all evil (or at least most of it) in programming. Donald Knuth

50 ... premature optimization is the root of all evil (or at least most of it) in programming. Donald Knuth

51 ... premature optimization is the root of all evil (or at least most of it) in programming. Donald Knuth

52 Command-line tools can be 235x faster than your Hadoop cluster Adam Drake

53 sort

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55 O(n log n)

56 O(n 2 )

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59 O(n!)

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61 OMG!

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63 O(n)

64 Simple Testing Can Prevent Most Critical Failures An Analysis of Production Failures in Distributed Data-Intensive Systems

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66 Schiaparelli s Inertial Measurement Unit (IMU) went about its business of calculating the lander s rotation rate. For some reason, the IMU calculated a saturationmaximum period that persisted for one second longer than what would normally be expected at this stage. When the IMU sent this bogus information to the craft s navigation system, it calculated a negative altitude.

67 That fateful miscalculation set off a cascade of despair, triggering the premature release of the parachute and the backshell, a brief firing of the braking thrusters, and activation of the on-ground systems as if Schiaparelli had already reached the surface. This all happened while the vehicle was still two miles (3.7 km) above ground.

68 A majority of the production failures (77%) can be reproduced by a unit test.

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73 Normally screws are so cheap and small and simple you think of them as unimportant. But now, as your Quality awareness becomes stronger, you realize that this one, individual, particular screw is neither cheap nor small nor unimportant. Robert M Pirsig Zen and the Art of Motorcycle Maintenance

74 Right now this screw is worth exactly the selling price of the whole motorcycle, because the motorcycle is actually valueless until you get the screw out. With this reevaluation of the screw comes a willingness to expand your knowledge of it. Robert M Pirsig Zen and the Art of Motorcycle Maintenance

75 Software Is Details