Introduction to
Computer Technology
Session_3
Systems Development Life
Cycle
Maud A. A. Elliot
0244887770
Session Objectives
• 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
2
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.
3
MANAGEMENT APPROACH
TO SYSTEMS DEVELOPMENT
• A system development from
management perspective is made up of
four phases,
1.
2.
3.
4.
Diagnosing information needs,
Evaluating information technology needs,
Designing responsive and
Implementing information system
4
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.
5
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.
• It consists of a set of steps or phases in
which each phase of the SDLC uses the
results of the previous one.
9
SDLC MODELS
•
•
•
•
Waterfall
Iterative Waterfall
Prototype
Evolutionary
10
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)
11
SDLC PHASES
Preliminary
Investigation
Maintenance
Analysis
Design
Implementation
Development
12
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.
15
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.
18
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
19
Implementation
• 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.
20
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.
21
The four changeover strategies
•
•
•
•
Direct cutover
Parallel operation
Pilot operation
Phased operation
22
Comparison of Changeover Strategies
Changeover
Advantages
Strategies
Direct cutover  Minimal cost
 Minimal work load
 Quick to implement
Parallel
 Build – in safety
Running
 Provides way of verifying
results of new system
Pilot
operation
Phased
changeover
Disadvantages.







High risk of failure
Could disrupt operation
If fails, will be costly.
Costly since two system need to be
operated
Time-consuming
Additional workload
Can take a long time to achieve total
changeover
Not as safe as complete parallel
running
 Less risky than direct
changeover
 Less costly then

complete parallel
running
 Less risky than a single
 Can take a long time to achieve
direct changeover
total changeover
 Other operations
 Interfaces between the parts of the
unaffected. Any problem
system may make this impractical.
23
is restricted to one area.
System evaluation (Maintenance)
• 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.
24
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.