Introduction to Computer Technology

Systems Development Life Cycle

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Akanferi Albert akanferi@yahoo.comakanferi@gmail.com

026-7023-177

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• Understand system development life cycle• Understand Management Perspective of

SDLC• Understand Technical Perspective of SDLC• Identify types of testing in systems

development• Identify systems changeover strategies

Session Objectives

Introduction• System development is a problem

solving procedure for examining the existing information system and improving upon it or developing a complete new system.

• System development can be viewed from two perspectives, Management and technical approaches.

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MANAGEMENT APPROACH TO SYSTEMS DEVELOPMENT• A system development from

management perspective is made up of four phases, 1. Diagnosing information needs, 2. Evaluating information technology needs, 3. Designing responsive and 4. Implementing information system

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Diagnosing information needs

• Diagnosing information needs of users involves identifying and describing the problem of the existing system.

• The context in which it occurs, the type of information available, the type of information required to solve the problem and the possible way of securing the needed information.

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Evaluating information technology needs• Evaluating hardware, software, database

and data communication of the company by assessing the current technology and systems, comparing available systems and selecting the technology that can address the problem.

Designing responsive systems

• It involves correcting the deficiencies in the existing or acquiring a complete new system to address the existing problem.

Implementing information systems• Implementation involves putting the

systems into action or operation.

TECHNICAL PERSPECTIVE (SDLC) • A process used by a systems analyst to

develop an information system, including requirements, validation, training, and user (stakeholder) ownership.

• The SDLC framework provides system designers and developers to follow a sequence of activities.

• Consists of a set of steps or phases in which each phase of the SDLC uses the results of the previous one.

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SDLC MODELS• Waterfall• Iterative Waterfall• Prototype• Evolutionary

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Software Development Life Cycle (SDLC PHASES)

• A system development from technical perspective is made up of six phases:

• Preliminary investigation,• Systems analysis, • Systems Design • Systems Development• Systems Implementation• System Evaluation (Maintenance)

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PreliminaryInvestigation

Analysis

DesignImplementation

Development

Maintenance

SDLC PHASES

Preliminary Investigation/ Problem Identification• It’s the initial idea of the project• Primary objective is to determine whether the

existing system is satisfying the goals and objectives of the organization.

• Forming project team and carrying out feasibility (Technical, economic, operational, schedule) studies.

• Establishing goals, selecting a system development method and submitting an investigation report.

Systems Analysis, Requirements Definition• It is the study of the existing system, its strength

and weakness. • It involves assembling an analysis team,

collecting and analyzing data, developing report on the existing system.

• Data collection seeks individual information about the problems and needs identified.

• Systems analysis goal is to determine where the problem is in an attempt to fix the system.

• Often there has to be a lot of communication to and fro to understand these requirements. 14

Systems Design• Determines the best system out of several

alternatives. • System design dimensions are conceptual design,

logical design and physical design. • Describes desired features and operations in detail,

including screen layouts, business rules, process diagrams, pseudo code and other documentation.

• The output of this stage is called system specifications.

• The design stage takes as its initial input the requirements identified in the approved requirements document.

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Data flow diagram and computer programs Flow charts

• Flow charts provide a graphical representation of the conceptualized and logical structure and sequence of operation in a program.

• The symbols in flow charts are

Terminator

Process

Arrow

Decision or control

Connector

Development• The real code is written here. • Modular and subsystem programming code

will be accomplished during this stage. • Unit testing and module testing are done in

this stage by the developers. • This stage is intermingled with the next in

that individual modules will need testing before integration to the main project.

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Types of Testing:• Defect testing• Path testing• Data set testing.• Unit testing• System testing• Integration

testing• Black box testing

• White box testing• Regression testing• Automation testing• User acceptance

testing• Performance testing

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Implementation

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• This phase places the new or modified systems into operation or action.

• The system put into action and staff given enough training on how to use the system.

• System change over may take the direct/immediate, parallel, pilot or phase approach.

• Changeover crisis are the problems associated with each change over method.

CHANGEOVER STRATEGIES• Now that a new system has been completely

developed, it should be implemented. • The process of replacing existing system with a

new one is termed changeover. • Changeover takes different approaches

depending on certain changeover factors such as:

• Costs, • System criticality, • User computer experience, • System complexity, • User resistance and • Time.

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The four changeover strategies• Direct cutover• Parallel operation• Pilot operation• Phased operation

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Comparison of Changeover Strategies

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Changeover Strategies

Advantages Disadvantages.

Direct cutover Minimal cost Minimal work load Quick to implement

High risk of failure Could disrupt operation If fails, will be costly.

Parallel Running

Build – in safety Provides way of verifying

results of new system

Costly since two system need to be operated

Time-consuming Additional workload

Pilot operation

Less risky than direct changeover

Less costly then complete parallel running

Can take a long time to achieve total changeover

Not as safe as complete parallel running

Phased changeover

Less risky than a single direct changeover

Other operations unaffected. Any problem is restricted to one area.

Can take a long time to achieve total changeover

Interfaces between the parts of the system may make this impractical.

• The purpose system evaluation is to keep the system operating efficiently and effectively.

• It involves the periodic evaluation or review of the system i.e. monitoring the system and ensures its operation.

• Involves making changes to the system, problems and major concerns come out and review can trigger the start of the complete system development process.

• This, the least glamorous and perhaps most important step of all, goes on seemingly forever.

• Maintaining the system is an important aspect of SDLC. • As key personnel change positions in the organization, new

changes will be implemented, which will require system updates.

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System evaluation (Maintenance)

Business strategic information systems

• The objectives of an organization define what the organization is trying to achieve.

• The objectives outline what the organization intends to do or the overall direction of the organization.

• To achieve the objectives of the organization, its critical success factors must be identified.

• Critical success factors are vital areas in an organization where things must be done right for the business to succeed or gain competitive advantage.

• Organizations should design information systems inline with their objectives.