Software Engineering Lecture # 1

What is Software? 2 Software is a set of items or objects that includes: programs data documents

Why is it important?

Importance of Software Software in everyday life Business decisions Products and services Technology and innovations Industry and entertainment Economic significance 4

Importance of Software … Software acts as basis for: Control of computer – operating systems Communication of information – internet Creation and control of other programs – software tools and environments 5

Hardware Vs. Software Hardware Wears out Replaceable spare parts Software Does not wear out No spare parts 6 Software characteristics: Intangible Exhibits aging Complex Deteriorates ( Decline, Depreciate ) Defect prone

Hardware Vs. Software … 7 Failure Rate Time Infant Mortality Wear out Hardware Failure Curve

Wear Vs. Deterioration 8 idealized / theoretical curve change actual curve Failure rate Time increased failure rate due to side effects Software deteriorates and becomes complex

The source of inherent complexity in software The difference between a software system and a car !!

Complexity in Software Complexity of software arises from Complexity of problem domain Difficulty in managing development process Software evolution Direct consequence of software change is software defects 10 The complexity of software is an essential property, not an accidental one

Cost of Software Software costs often dominate system costs. The costs of software on a PC are often greater than the hardware cost Software costs more to maintain than it does to develop. For systems with a long life, maintenance costs may be several times development costs 11

The Cost of Change 12 Definition Development After release 1x 1.5-6x x

13 The name of the game is continuous change and evolution in all dimensions!

Engineering The study concerned with putting scientific knowledge to practical use Webster’s Dictionary 14

Engineering… A way of approaching a problem An approach to productively use scientific knowledge Examples: Electrical Engineering Mechanical Engineering Civil Engineering 15 Physics as basic science

Difference between Computer Science and Software Engineering 16 Software Engineering uses knowledge from Computer Science to effectively build software

Software Crisis A Historical Perspective (1950’s) The advent of more powerful and cheaper hardware resulted in more complex applications. The tools and technologies for primitive computer systems were inadequate for newer systems Resulted in Prolonged schedule slippages Astronomical development and maintenance costs Unreliable software systems Disappointment !!! Software was in Crisis 17

The Birth of Software Engineering Born in 1960 in a conference on Software Crisis Software Crisis resulted in realization that: 18 “Coding” alone was not enough!! New techniques and methods were required to control the complexity inherent in “LARGE” software systems

The Birth of Software Engineering… Decision There should be some engineering principles applied for the development of successful software 19 The Term ‘Software Engineering’ was coined

Software Engineering-Definitions IEEE The application of a systematic, disciplined, quantifiable approach to the development, operation, and maintenance of software; that is, the application of engineering to software 20

Software Engineering-Definitions Ian Sommerville- All aspects of software production: Software engineering is not just concerned with the technical processes of software development, but also with activities such as software project management and with the development of tools, methods and theories to support software production 21

Software Engineering 22 Software Engineering is not just about producing software, but about producing software in a COST- EFFECTIVE manner. The set of processes and tools to develop software

Software Engineering: Points to Remember SE is has a wide scope and is concerned with anything that has something to do with software SE is concerned with cost effective software development SE is NOT just coding; there is a lot more to it 23 SE is nothing but a disciplined and systematic approach to developing software

No Silver Bullet Fred Brooks, “The Mythical Man-month” There is no short cut to software development Software can be disastrous to managers in the form of: Schedule slippages High costs Delivery of unreliable systems 24 Begin upright and upfront with a systematic approach to building software

Characteristics of a Well Engineered Software Provides the required functionality Maintainable 25  Efficient  User-friendly  Cost-effective Reliable

A software engineer is challenged to produce high- quality software with a finite amount of resources, within predicted schedule and budget 26

The Balancing Act Software requirements may be conflicting Cost vs. Efficiency Cost vs. Reliability Efficiency vs. User-interface 27

Challenge is to balance these requirements 28

Effort Breakdown Breakdown of activities involved in software development (Caper Jones) Project Management 8.08% Requirements 14.43% Design 11.36% Coding13.50% SQA30.64% SCM13.02% Integration6.54% Miscellaneous ~3% 29 SE is NOT just Coding !!

Software Engineering is nothing but a disciplined and systematic approach to software development! (In a cost effective manner) 30