CSC100AB – C++ Programming

Introduction to Software EngineeringAnd Program Design

What is Software?What is Software Engineering?

What Does Software Engineering Do?How is Software Engineered (Process)?

Software Engineering vs. Computer Science?

What is Software?• Software is the Definition and Organization of a Set

of Tasks and Functionality Encapsulated into a Form that is Executable on a Computer

• What are Different Types of Software?– Commercial-Off-the-Shelf (COTS)– Government-Off-the-Shelf (GOTS)– Legacy: Written in an “Old” Programming Language

• Cobol, PL/1 (Y2k/SNET), Fortran, etc.• C and C++!

– Customized New Software– Client vs. Server Software– Database Management Systems/Applications

What is Software Engineering?• Engineering: The Application of Science to the Solution of

Practical Problems• Software Engineering: The Application of CS to Building

Practical Software Systems • Programming

– Individual Writes Complete Program– One Person, One Computer– Well-Defined Problem– Programming-in-the-Small

• Software Engineering– Individuals Write Program Components– Team Assembles Complete Program– Programming-in-the-Large

What is Software Engineering?• The Application Of Engineering To Software• Field of CSE Dealing with Software Systems

– Large and Complex– Built By Teams– Exist In Many Versions– Last Many Years– Undergo Changes

• Definitions:– Application of a Systematic, Disciplined, Quantifiable Approach to

the Development, Operation, and Maintenance of Software (IEEE 1990)

– Multi-person Construction of Multi-version Software (Parnas 1978)

Why Software Engineering?• Program Complexity Transcends Individual or Lone

Programmer• Software Engineering Targeted for

– Constructing Large Software Applications– Defining Problem Clear and Completely– Tools and Techniques to Support Process– Team-Oriented Experience

• Software Engineering must Evolve to be an Engineering Discipline

• Software Engineering Must Promote and Support Multi-Person Construction of Multi-Version Software

Software Engineering - Historically• “Early Days”

– 1950’s Programmers Wrote Programs– Early 1960’s - Very Large Software Projects Constructed by

“Experts”– Mid-Late 1960’s - Advent of Large Commercial Software

Applications• Large Systems Involved Teams of Individuals• Coining the Term “Software Engineering”

• Towards a Software Engineering Discipline– Individuals Couldn’t see “Big Picture”– Increase in Communication Time– Personnel Changes Impact on Productivity

• SE: Management, Organization, Tools, Theories, Methodologies, Techniques, etc.

Influences on Software Engineering• Cost of Software Continues to Increase, Requiring

More Efficient Software Production– Software Acquisition vs. Outsourcing– Software Reuse vs. Build-from-Scratch

• Complexity of Large Software Altered the View from Development PerspectiveConception Design DevelopmentIntegrationDistribution DocumentationMaintenance Evolution Extension

• Software Engineering/Computer Science Growth– 350,000 Information Technology Jobs Open– 100,000 New Jobs per Year for 10 Years

Programmer vs. Software EngineerPROGRAMMER• Individual with Good Skills• Programming-in-the-Small• Knowledge on

– Data Structures– Algorithms

• Fluent in Several Programming Languages• May Lack Formal Training• Minimal Exposure to CS

Programmer vs. Software EngineerSOFTWARE ENGINEER• Part of a Team• Programming-in-the-Large• Design Approaches

– OO, Modules, etc.– Top-Down/Bottom-Up

• Translates Requirements into Specifications• Familiarity in Multiple Application Areas• Converses with Users• Sees “Big Picture”• Can Model Application• Good Communication and Interpersonal Skills

Waterfall Process ModelRequirements Analysis andSpecification

Design andSpecification

Coding andModule Testing

Integration andSystem Testing

Delivery and Maintenance

50 %

50 %

What is the Major Disadvantage?

Software Lifecycle of Waterfall Model

• Requirements Analysis and Specification– What is the Problem to Solve?– What Does Customer Need/Want?– Interactions Between SE and Customer– Identify and Document System Requirements– Generate User Manuals and Test Plans

• Design and Specification– How is the Problem to be Solved?– High-Level Design– Determine Components/Modules– Transition to Detailed Design– Detail Functionality of Components/Modules

Software Lifecycle of Waterfall Model

• Coding and Module Testing– Writing Code to Meet Component/Module Design Specifications– Individual Test Modules in Isolation– Drivers and Stubs to Simulate Behavior

• Integration and System Testing– Integration of Components/Modules into Subsystems– Integration of Subsystems into Final Program

• Delivery and Maintenance– System Delivered to Customer/Market– Bug Fixes and Version Releases Over Time

• Advantages of waterfall model:

• Simple and easy to understand and use.• Easy to manage due to the rigidity of the model – each phase has specific deliverables and a review

process.• Phases are processed and completed one at a time.• Works well for smaller projects where requirements are very well understood.

• Disadvantages of waterfall model:• Once an application is in the testing stage, it is very difficult to go back and change something that was

not well-thought out in the concept stage.• No working software is produced until late during the life cycle.• High amounts of risk and uncertainty.• Not a good model for complex and object-oriented projects.• Poor model for long and ongoing projects.• Not suitable for the projects where requirements are at a moderate to high risk of changing.

• When to use the waterfall model:• Requirements are very well known, clear and fixed.• Product definition is stable.• Technology is understood.• There are no ambiguous requirements• Ample resources with required expertise are available freely• The project is short.

RAD (Rapid Application Development) MODEL

Phases of RAD• Business modeling: The information flow is identified between

various business functions.•

Data modeling: Information gathered from business modeling is used to define data objects that are needed for the business.

•Process modeling: Data objects defined in data modeling are converted to achieve the business information flow to achieve some specific business objective. Descriptions are identified and created for CRUD (Create, Read, Update, Delete) of data objects.

•Application generation: Automated tools are used to convert process models into code and the actual system.

•Testing and turnover: Test new components and all the interfaces.

Advantages of the RAD model:Reduced development time.Increases reusability of componentsQuick initial reviews occurEncourages customer feedbackIntegration from very beginning solves a lot of integration issues.Disadvantages of RAD model:Depends on strong team and individual performances for identifying business requirements.Only system that can be modularized can be built using RADRequires highly skilled developers/designers.High dependency on modeling skillsInapplicable to cheaper projects as cost of modeling and automated code generation is very high. When to use RAD model:RAD should be used when there is a need to create a system that can be modularized in 2-3 months of time.It should be used if there’s high availability of designers for modeling and the budget is high enough to afford their cost along with the cost of automated code generating tools.RAD SDLC model should be chosen only if resources with high business knowledge are available and there is a need to produce the system in a short span of time (2-3 months).

Prototyping Model

• The basic idea here is that instead of freezing the requirements before a design or coding can proceed, a throwaway prototype is built to understand the requirements.

• This prototype is developed based on the currently known requirements. By using this prototype, the client can get an “actual feel” of the system, since the interactions with prototype can enable the client to better understand the requirements of the desired system.

• Prototyping is an attractive idea for complicated and large systems for which there is no manual process or existing system to help determining the requirements.

• The prototype are usually not complete systems and many of the details are not built in the prototype. The goal is to provide a system with overall functionality.

• Advantages of Prototype model:• Users are actively involved in the development• Since in this methodology a working model of the system is provided, the users get a better understanding of the

system being developed.• Errors can be detected much earlier.• Quicker user feedback is available leading to better solutions.• Missing functionality can be identified easily• Confusing or difficult functions can be identified

Requirements validation, Quick implementation of, incomplete, butfunctional, application.

• Disadvantages of Prototype model:• Leads to implementing and then repairing way of building systems.• Practically, this methodology may increase the complexity of the system as scope of the system may expand

beyond original plans.• Incomplete application may cause application not to be used as the full system was designed

Incomplete or inadequate problem analysis.

• When to use Prototype model: • Prototype model should be used when the desired system needs to have a lot of interaction with the end users.• Typically, online systems, web interfaces have a very high amount of interaction with end users, are best suited

for Prototype model. It might take a while for a system to be built that allows ease of use and needs minimal training for the end user.

• Prototyping ensures that the end users constantly work with the system and provide a feedback which is incorporated in the prototype to result in a useable system. They are excellent for designing good human computer interface systems.

SWE Other Disciplines• SWE and Management

– Management/Team Models Applied to Software Project Management/Process Control

– Important Test Domain to Test New Models and Theories for Management

• SWE and EE, ME, ChemE, CivilE, etc. – Job Growth in Engineering Specific Software

• SWE and Biology, Chemistry, Medicine, etc.– Medical Research and Informatics, Genome

• SWE and Financial Sector– Banking, ATM Networks, Electronic Commerce, Funds Transfers,

Program Trading, Stock and Brokerage Houses, etc.

Motivation and Background Concepts

• Information Engineering for 21st Century– Creation of Information– Generation of Information– Utilization of Information– Software, Database, Security, Performance Requirements for Application D

& D– From Centralized to Distributed Solutions

• Tracing the History– Abstract Data Types (ADTs) - 1970s– Object-Oriented Paradigm - 1980s– Component-Based D & D – 1990s– Web-Based/Distributed Computing – 2000s– 20xx + - Cloud Computing and Virtual Machines

How is Information Engineered?• Careful Thought to its Definition/Purpose• Thorough Understanding of its Intended Usage and Potential

Impact• Insure and Maintain its Consistency

– Quality, Correctness, and Relevance • Protect and Control its Availability

– Who can Access What Information in Which Location and at What Time?

• Long-Term Persistent Storage/Recoverability– Cost, Reusability, Longitudinal, and Cumulative Experience

• Integration of Past, Present and Future Information via Intranet and Internet Access

Challenge for 21st Century• Timely and Efficient Utilization of Information

– Significantly Impacts on Productivity– Key to Many (All?) Companies Future– Supports and Promotes Collaboration for Competitive Advantage– Individual/Companies Use Information in New and Different Ways

• Collection, Synthesis, Analyses of Information– Better Understanding of Processes, Sales, Productivity, etc.– Dissemination of Only Relevant/Significant Information - Reduce

Overload• Fact: We Live in an Increasingly Information Centered Society!

Future Design Emphasis• Focus on Information and its Behavior• Answer the Following Questions

– What are Different Kinds of Information?– How is Information Manipulated?– Is Same Information Stored in Different Ways?– What are Information Interdependencies?– Will Information Persist? Long-Term DB? Versions of Information?– What Past Info. is Needed from Legacy DBs or Applications?– Who Needs Access to What Info. When?– What Information is Available Across WWW?– Is Processing Distributed? How are Distributed Artifacts Accessed?

Replicated? Designed?

2000s – Web/Distributed Applications

• Distributed Computing/Applications are …– Systems of Systems– Interoperation of New & Existing Applications– Legacy, Databases, COTS, New Clients, etc.– Network Centric Environment– Multi-Tier Solutions

• Distributed Computing Applications must …– Manage, Control, Access, and Modify Data– Allow Humans to Interact with Data– Provide High-Availability and Performance– Evolvable Over Time

• Present & Future Systems Exhibit All of These Characteristics and More!

What is a Distributed Application?

JavaClient

JavaClient

LegacyClient

DB Client

COTSClient

LegacyDatabase

Server

Legacy

COTSServer

Database

COTS

Network Centric EnvironmentHigh-AvailabilityPerformanceHeterogeneity

Hardware OS, PLs

Transparent Interoperation New/Innovative Information Use

Increase ProductivityDynamic

Environment

System of Systems

Another View – Today’s Reality

Legacy

Legacy

COTS

GOTS

Database

Database

NETWORK

JavaClient

GOTSClient

LegacyClient

DatabaseClient

COTSClient

Today’s Reality

• Premise: Artifacts - set of– DB, Legacy, COTS, Each w/ API

• Premise: Users– New and Existing– Utilize Artifact APIs

• Distributed Application, DA– Artifacts + Users

• What are the Issues?– How Do they Interact?– Heterogeneity– Security Concerns– Different Programmatic Models– Etc. Etc. Etc.

Why is Distributed Computing Needed?

• Today’s Environments Contain Applications … – Created with Multiple Programming Languages– Executing on Heterogeneous Platforms– Locally and Geographically Distributed

• Distributed Computing Applications Must … – Allow Seamless and Transparent Interoperation– Provide Tools for Engineers and Users

• Result: Inter-Operating Environment – Utilize Information in New/Innovative Ways– Leveraged to Increase Productivity – Support Diverse User Activities– Dynamically Respond to Changes

Why a Distributed Application?

• Reasons:– Data used is Distributed– Computation is Distributed– Application Users are

Distributed• 2 Key Issues for Solution:

– Platform-Independent Models and Abstraction Techniques

– Hide Low-Level Details– Provide a Well-Performing

Solution– Works Today and Tomorrow!

Shared Objects

• Easy to Re-use• Easy to distribute• Easy to maintain

Striving for New Techniques/Technologies

• We Must Diverge from Business as Usual– C Programming with RPC– Customized Development without Reuse– Solutions that Aren’t Extensible and Evolvable– Cobbling Together Solutions w/o Method or Reason is

Unacceptable and Doomed to Fail!• We Must Face Today’s Realities

– Legacy Code is Fact of Life– New Technologies Offer New Challenges– Adopt to Leverage Their Benefits– We Must Draw Careful Balance to Opt for Mature Technologies

While Targeting Emerging Technologies with Potential!

Who are the Players?

• Stakeholders– Software Architects (Requirements)– System Designers (Solutions)– Application Builders (Implementation)

• Stakeholders Striving to Provide …– System Interaction and Information Exchange– Utilization of Existing Applications in New and Innovative Ways

• End-Users at Various Skill Levels and with Specific and Limited Access Requirements– Novice vs. Adept vs. Expert– Who Uses What When and for How Long?

Summary• Computing is Pervasive Throughout Society!• Software Engineering has Not Kept Pace as a Discipline to Hardware

Advances– CPU Speed (and Multi-Processors)– Memory Size

• 1982: PDP 11/44 with 256K• 1993: Sun 4 with 32M• 1997: Sun Ultra with 64M/PC with 32 M• 1998: Suns and PCs with 128M • 2006: PCs with 1-2 Gigabytes of RAM• 2010: PCs with 8+ Gigabytes of RAM

– Disk Capacity• 1982: 60M with 2’ by 3’ by 3’ Footprint• 1993: 200M inside your PC• 1997: 2 to 4 G inside your PC• 1998: 8 or more G inside your PC• 2006: PCs with 160G+, NW Storage Devices, etc.• 2010: PCs with 1TB+, USB Flash Drives 64 GB+, Solid State Disk Drives 100 GB+

SUMMARY

• Software Becoming More Complex and Appearing in More and More Places (Embedded Computing)

• Software Engineering Must Evolve to Embrace Engineering Concepts, Approaches, and Rigor!– Technology

• Component-Based, Distributed, Web, etc.• Software Engineering for …

– Education• Software Engineering MS Degrees • Software Engineering BS Degrees