SOFTWARE ENGINEERING ppt

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SOFTWARE ENGINEERING:

SOFTWARE ENGINEERING Given By – Miss Swarna Singh Prepare By – Akash Deep Katiyar Saurabh Kumar Chaturvedi Upendra Kumar Chaturvedi Software Engineering: Introduction 1

Objectives:

Objectives What is Software Engineering? Why Software Engineering? How to do Software Engineering? Software Engineering: Introduction 2

What is Software Engineering? :

What is Software Engineering? Software Engineering = Software + Engineering What is Software ? Software = Soft + ware Any examples? What is Engineering ? Engineering = Engine- er - ing Any examples? Is this an Engineering discipline? If yes, why? If not, why not? Is this for an Engineer or a scientist? Software Engineering: Introduction 3

What is Software Engineering? :

What is Software Engineering? A historical definition: “The establishment and use of sound engineering principles in order to obtain economically software that is reliable and works efficiently on real machines …” [Fritz Bauer, at the 1 st NATO Conference on Software Engineering, 1969] IEEE definition: “Software engineering is the application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software.” A shorter definition: BCFH Software Engineering: Introduction 4

Why Software Engineering? :

Why Software Engineering? Software Engineering: Introduction 5 Used w. extensive rework, but later abandoned 20% Used as delivered 2% Usable w. rework 3% 9 software projects totaling $96.7 million: Where The Money Went [Report to Congress, Comptroller General, 1979] Delivered, but never successfully used 45% Paid for, but not delivered 30% Why? Software hurts Requirements design

What Factors Contribute to Project Success?:

What Factors Contribute to Project Success? Software Engineering: Introduction 6 10. Other 9. Reliable Estimates 8. Formal Methodology 7. Firm Basic Requirements 6. Standard Software Infrastructure 5. Minimized Scope 4. Clear Business Objectives 3. Experienced Project Manager 2. User Involvement 1. Executive Management Support The CHAOS Ten Standish Group, ‘01 (www.standishgroup.com) Project Success Factors 28% 49% 23% completed on time and on budget canceled before completion overran original estimates: Time overrun averaged 63% - Cost overrun averaged 45%

What Factors Contribute to Project Failure?:

What Factors Contribute to Project Failure? Software Engineering: Introduction 7 The CHAOS Ten The CHAOS Ten “The definition of insanity is doing the same thing over and over again and expecting a different result.” [ Albert Einstein ]

Why Software Engineering? :

Why Software Engineering? Software Engineering: Introduction 8 Work alone 20% What do software engineers do? Non-productive Activities 30% Interaction 50% programming ≠ software engineering personal activity team activity small, clear problem large, nebulous problem

Why Software Engineering? :

Why Software Engineering? http://www.cis.gsu.edu/~mmoore/CIS3300/handouts/SciAmSept1994.html http://techdirt.com/articles/20060818/1613226.shtml Software Engineering: Introduction 9 Are you aware of any other mishaps?

Why Software Engineering? :

Why Software Engineering? Major symptoms of the “software crises”: Over budget Schedule slippage Poor quality Major causes of the “software crises”: The "software crises" came about when people realized the major problems in software development were … caused by communication difficulties and the management of complexity ” [Budd] Software Engineering: Introduction 10

Why SE?:

Why SE? Software Engineering: Introduction 11

Slide 12:

Software Engineering: Introduction 12 Systems Engineering Requirements Analysis Project Planning Architectural Design Detailed Design Implementation Release Maintenance Quality Assurance Software Lifecycle Review How to Do Software Engineering? BCFH - models/languages, processes/methodologies, tools, …

To be discussed later on…:

To be discussed later on… Software Engineering: Introduction 13

How to do SE? :

How to do SE? Software Engineering: Introduction 14

How to do SE? :

How to do SE? Software Engineering: Introduction 15

The Tar Pit:

The Tar Pit The woes of the craft: Bugs!!! Bugs get harder as testing progresses The fundamental problem: fixing a bug has a 20%-50% chance of introducing another The product gets obsolete upon or even before completion Worse: must use others’ programs! Software Engineering: Introduction 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Slide 17:

Genesis 11:1-9 Acts 2:1-4 The Tower Of Babel Let's become famous by building a city with a tower that reaches up to heaven (verse four). Let's go down and confuse their speech right away, and make it so that they will not understand each other's speech. (verses five through seven). Software Engineering: Introduction 17

Why Did the Tower of Babel Fail?:

Why Did the Tower of Babel Fail? Software Engineering: Introduction 18 Bad communication in software projects is the root of all evil .

The Mythical Man-Month :

The Mythical Man-Month Optimism: All programmers are optimists, believing in happy endings and fairy god-mothers. Because programming tasks are usually chained end-to-end, the probability that each will go well is very small. Man-month: Cost vary as a product: men · months . Progress does not: communication overhead! Overhead: intercommunication and training. Software Engineering: Introduction 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Brook’s Law:

Brook’s Law Adding manpower to a late software project makes it later . Software Engineering: Introduction 20

Hatching a Catastrophe:

Hatching a Catastrophe Poor Project planning, estimation, control Coding is “ 90% finished ” for half of the total coding time Debugging is “ 99% complete ” most of the time Software Engineering: Introduction 21

No Silver Bullet – Essence and Accident in Software Engineering:

No Silver Bullet – Essence and Accident in Software Engineering “There is no single development, in either technology or management technique, which by itself promises even one order-of-magnitude improvement within a decade in productivity, in reliability, in simplicity” (1986) . Complexity enormous number of states (orders of magnitude more than in hardware), so conceiving, describing and testing is hard increases non-linearly with its size introduces a lot of difficulties: communication among team members enumerating (much less understanding) of all possible states of the program management problems: conceptual integrity is hard to achieve learning curve: personnel turnover becomes disaster others Software Engineering: Introduction 22

The M-MM after 20 years :

The M-MM after 20 years Answers questions like: What do you now think was wrong when written? What is now obsolete? What is really new in the software engineering world? Software Engineering: Introduction 23 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 What was right and still is: Conceptual integrity is the more important factor in ease of use [There are other factors. Consider Macintosh vs. MS-DOS]. It is the central question addresses by M-MM and is central to product quality.

How to do SE? :

How to do SE? Software Engineering: Introduction 24

How to do SE? :

How to do SE? Software Engineering: Introduction 25

How to do SE? :

How to do SE? Software Engineering: Introduction 26

How to do SE? :

How to do SE? Software Engineering: Introduction 27

How to do SE? :

How to do SE? Software Engineering: Introduction 28

How to do SE? :

How to do SE? Software Engineering: Introduction 29

Slide 30:

Software Engineering: Introduction 30 Why speak about management rather than technical issues?

How to do SE? :

How to do SE? News Groups: comp.software -eng comp.software.testing … Professional Organizations: IEEE: TSE, ICSE, ICRE, … ACM: TOSEM … Software Engineering: Introduction 31

Introduction to SE - Summary:

Introduction to SE - Summary Why Software Crisis due to Communication and Complexity Inherent complexity What Engineering (large) software, bcfh How BCFH languages, concepts, models, tools Software Engineering: Introduction 32

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Software Engineering: Introduction 33

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Software Engineering: Introduction 34

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Software Engineering: Introduction 35

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Software Engineering: Introduction 36

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Software Engineering: Introduction 37

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Software Engineering: Introduction 38

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Software Engineering: Introduction 39

Introduction to SE - Points to Ponder:

Introduction to SE - Points to Ponder Programming = software engineering? What does BCFH really mean? Can you define it completely? What are the similarities, and differences, between Civil Engineering and Software Engineering? What are the differences between a notation and a methodology? Can we use C# for analysis? Can you prove you and I communicate with each other perfectly? Are you a scientist or an engineer? Software Engineering: Introduction 40

Slide 41:

Thank you for your presence Software Engineering: Introduction 41

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