Lecture 2 ASE

8/3/2019 Lecture 2 ASE

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What is Software Engineering?

An engineering discipline. Covers all aspects of software production

From system specification to maintenance.

Engineering: Selective selection of theories, tools and methods to

discover solutions to problems.

It is working under organizational and financialconstraints.

All aspects: Not only technical but also SW project management

and development of tools etc.


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SE vs. CS

CS is concerned with theory and

fundamentals.

SE is concerned with the practicalities ofdeveloping and delivering useful software.

Ideally, all of SE should have a strong CS basis,

but this doesnt happen every time ad hoc

approaches


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System engineering vs. SE

System engineering

Concerned with all aspects of the development

and evolution of complex systems where software

plays a major role.

Hardware development, policy and process

design, system deployment, SE.

E.g. air craft and chemical plants.


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Software process

A set of activities and associated results thatproduce a software product.

Four fundamental process activities:

Software specification Requirements

Software development Design and program

Software validation Testing

Software evolution Maintenance


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Software process model

A simplified description of a software process.

Three general software process models:

The waterfall approach

The four process activities are represented as separate processphases (reqt specification, sw design, implementation, testing ).

After each phase is defined, it is signed-off and development goesto the following phase.

Iterative development

Interleaving of the four process activities. Improvement in software in subsequent iterations.

Component-based software engineering

Integrating already developed parts of the system.


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Nature of Software

System software

Application software

Engineering/scientific

software

Embedded software

Web applications

AI software

Operating systems

To solve specific need

To deal with calculations

Resides within the product

a set of linked hypertext files

to present information

Uses algorithms to solve

complex problems

Broad categories of computer software are:


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System & Application Software


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System Software

The software that is an essential part of thecomputer system

A collection of programs written to service other

programs

Compilers, editors, file management utilities

System software heavily interact with computer

hardware

Operating system

Resource sharing


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Application Software

Consists of standalone programs to solvespecific need

Also called end-user programs includes

database programs, word processors, andspreadsheets

Applications software sits on top of systems

software because it is unable to run without

the operating system


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Engineering/ Scientific Software

Deals with algorithms, Scientificnotations

Automotive stress analysis to space shuttle

orbital dynamics Molecular technology to automotive

manufacturing


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Embedded Software

Resides with in a product or system and

used to implement and control the

feature and function of the system Can perform a limited functions

Microwave oven

Fuel control Temperature control


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Web Applications

WebApp a wide variety of applications can be a set of linked hypertext files that

present information using text and graphics

As e-commerce integrate corporatedatabases and business application


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Artificial Intelligence Software

Uses algorithms to solve complex problems

Applications in this area includes

Robotics

Expert system Pattern recognition

Neural networks


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Legacy Software

Legacy software systems are programs that are oftencritical to the operation of companies

These programs were developed years ago and, use early

programming languages such as COBOL and FORTRAN

These programs have been maintained for many years

by various programmers

Because of the years of changes that have been made tothe software, supporting documentation may not be

current and the authors may no longer be available

Without either the full documentation, or the personnel whounderstand the code, changes to these programs can be hard

to accomplish, expensive, and should not be taken lightly


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Legacy Software

software must be adapted to meet the needs

of new computing environments or

technology.

software must be enhanced to implementnew business requirements.

software must be extended to make it

interoperable with other more modern

systems or databases. software must be re-architected to make it

viable within a network environment.

Why must it change?


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Software Myths

Rumors. Half-truths. Cautionary tales A significant number of "myths" surround software quality,

development and testing practices

Affect managers, customers and practitioners

Are believable because they often have elements oftruth,

but

Invariably lead to bad decisions,

therefore Insist on reality as you navigate your way through

software engineering


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Software myths

Three types of myths:

Management myth

Customer myth Practitioner/Developer myth


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Management myths

We have standards and procedures for building

software, so developers have everything they

need to know.

We have state-of-the-art software

development tools; after all, we buy the latest

computers.

If we're behind schedule, we can add moreprogrammers to catch up.

A good manger can manage any project.


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Customer myths

A general statement of objectives is sufficient

to begin writing programs - we can fill in the

details later.

Requirement changes are easy toaccommodate because software is flexible.

I know what my problem is; therefore I know

how to solve it.


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Practitioner/Developer myths

If I miss something now, I can fix it later.

Once the program is written and running, my job

is done.

Until a program is running, there's no way ofassessing its quality.

The only deliverable for a software project is a

working program.

Documents

Lecture 2 ASE