Systems development cycle

SYSTEM DEVELOPMENT
CYCLE
Wednesday, January 25, 2017

LEARNING OUTCOMES
At the end of the lesson, I should be able to:
a) -Define system development cycle
b) -Describe system development cycle
c) -Describe subsystems
d) -Draw a system development
e) -Stages in system development life cycle
f) -Advantage & Disadvantages of system development cycle

The systems development life cycle (SDLC), also
referred to as the application development life-
cycle, is a term used in systems engineering,
information systems and software engineering to
describe a process for planning, creating, testing,
and deploying an information system.
DEFINITION

Requirements for a successful development of information
system:
1. Thorough system analysis and design,
2. Understanding what the business or organization
requires.
Note:
System analysis is the process of understanding in detail
what a system should accomplish, how it will accomplish it
and what is required to accomplish it.
System design is the process of specifying in details how
components of an information system should be
implemented physically.
System analyst is a person that uses analysis and design
techniques to solve business problems using information
technology.

SKILLS OF A SYSTEM ANALYST:
1. Understand business problems
2. Always wanting the improvement of the
system
3. Information technology (IT) knowledge and
programming expertise
4. Ability to find facts about the problem and
develop how it should be solved
5. Use logical methods to solving problems
6. People management knowledge and skills

THE CONCEPT OF SYSTEMS
A system is a collection of interrelated components that function
together to form a whole and achieve an outcome.
An information system is a collection of interrelated components
that collect, process, store and provide as an output the information
needed to complete a task. An information system can also be
defined as a collection of programs running on computers which
interact with each other as well as humans to provide the necessary
information needed to make decisions within an organization.
A subsystem is a part of a larger system that can function on its own
to perform a task.
The components that make up a computer system can be described
as subsystems; consisting mainly hardware and software subsystems.

COMPONENTS OF
INFORMATION SYSTEMS:
1. IT (hardware and software)
2. Data/Information
3. Procedures/Policies
4. People
5. Communication Networks

TYPES OF INFORMATION
SYSTEMS:
1. Transaction processing systems
2. Management information systems
3. Decision support systems
4. Executive information systems

WATERFALL SDLC MODEL
The Waterfall Model is used to describe how system
development flows downwards through the phases.
Hence, the term System Development Life Cycle is used to
describe the sequence of steps that are followed when
building a new ICT system. Each step or phase in the
development cycle consists of a series of activities.

STAGES IN SYSTEM DEVELOPMENT
LIFE CYCLE (SDLC)
1. Investigation & Analysis - Look at the existing
system and find Improvements
2. Design - Plan the proposed new system
3. Development and Testing - Create the new system
and test it
4. Implementation - Place the new system into the
company
5. Documentation - Create user-guides for every day
users and those technicians who will develop it further
6. Evaluation and maintenance - Decide how well the
new system is working.

WHAT DOES INVESTIGATION &
ANALYSIS INVOLVE?
# Typical investigation analysis would involve the following:
1. Collecting data about the current system / proposed
system(what needs changing, what is working well, what
needs to be improved upon etc.)
2. Find out problems with the current system
3. Establish the problem that the customer needs solving
(What does the new system need to be able to do? - e.g.
calculate employee pay)
4. Identify inputs, processing and outputs of the current /
proposed system (What needs to go into the system?, what
calculations?, what needs to come out?)
5. Identify the requirements of the new system (What tasks
should the system be able to handle?)
6. Producing a cost-benefit analysis (Is it worth it financially
to build the system?).

HOW IS THIS DATA
OBTAINED?
#There are four methods which are used to
obtain this information:
1. Questionnaires
2. Interviews
3. Observing people using the current system
4. Looking at the current system's
documentation

DESIGN
This is where the new system is planned thoroughly to make
sure that the developers know how each screen should look
and how the system should work.

WHAT DOES DESIGN INVOLVE?
1. Designing data entry screens(how will data be entered into
system.... e.g. text boxes, drop-down menus etc)
2. Designing user-interface layouts (what will the system's
menus, search facilities etc look like?)
3. Designing printed outputs (reports etc)(what will printed
outputs look like.... e.g. payslip's, customer bills etc)
4. Designing screen-based outputs (what will outputs that are
displayed on the screen look like?)
5. Designing structures to store data(e.g. for databases, tables
will need to be designed to hold the system's records)
6. Designing data validation methods - (how will the system
prevent invalid / incorrect data from being entered?)
7. Designing data verification methods - (how will the system
check that entered data is correct?)

DESIGNING SYSTEM
VALIDATION
Validation is where a computer system checks that data
entered by the user is sensible and usable.

DESIGNING SYSTEM
VERIFICATION
Verification is a way of making sure that data being entered
into the system exactly matches the source of the data.

DEVELOPMENT & TESTING
System development just means to 'build the system'. A system's
developer will follow the designs to produce a working system that
meets all requirements.

WHAT ARE THE STAGES OF
DEVELOPMENT?
The development stage is broken down into 4 parts:
1. Creating a file structure to store data
2. Create validation rules to make sure that data entered is sensible
3. Create a user-interface to allow data to be entered into the
system
4. Create output formats (reports, pay slip's, bills etc.)

TESTING THE SYSTEM
A test plan is usually written whilst the system is
being developed. The test plan will contain details
of every single thing that needs to be tested.
A typical test would contain:
i. Details of what is being tested
ii. The test data to use
iii. What is expected to happen when the test is
performed

Test plans are very detailed, and contain many tests.
Each test is specified very precisely.
For example:
1. Does the system open and close properly?
2. Can data be entered?
3. Can data be saved?
4. Can reports be printed?
5. When you do something wrong, does an error
message appear?
6. Is invalid data rejected? E.g. if you are not allowed to
enter an amount above £1,000 on the system then a
value of 1,001 should not be accepted (i.e. does the
validation work?)

SELECTING TEST DATA
When choosing what data to use to test a
system, you need to think about why we
are testing the system: to see if it works,
and to check it doesn't break.
To do this, we use three types of test data...

NORMAL DATA VALUES
This is data that would normally be entered into the system.
E.g. In a system that was designed to accept and process test
marks (percentages), then normal test values would include:
10
25
63
89

EXTREME DATA VALUES
Extreme value are still normal data.
However, the values are chosen to be at the absolute
limits of the normal range.
E.g. In a system that was designed to accept and process
test marks (percentages), then extreme test values would
be:
0 (lowest possible value)
100 (highest possible value)
In systems that deal with text, the extreme values are
defined by how long the text can be. The limits would be:
"" (nothing entered)
"ABCDEF..." (max. length)

ABNORMAL DATA VALUES
This is data that should not normally be accepted by the
system - the values are invalid.
E.g. In a system that was designed to accept and process test
marks (percentages), then abnormal test values would include:
-1
101
200
-55

Testing is done in two phases:
Phase 1 – Done by designers and engineers who created the
system before it is delivered to the customer.
Pase2 – Done after the system has been delivered and
installed with the customer.

WHAT HAPPENS IF THE SYSTEM FAILS
SOME TESTS?
If any failures are found, the systems
analyst goes back and does some further
research, analysis and design to fix these
areas.

SYSTEM DOCUMENTATION
There are two types of documentation that should be
produced when creating a new system:
1. User documentation
2. Technical documentation

USER DOCUMENTATION
User documentation usually includes:
1. List of minimum hardware and software required
to use the system
2. How to install the system
3. How to start / stop the system
4. How to use the features of the system
5. Screenshots showing the system in typical use
6. Example inputs and outputs
7. Explanations of any error messages that might be
shown
8. A troubleshooting guide

TECHNICAL DOCUMENTATION
Technical documentation usually includes:
1. Details of the hardware and software required for the
system
2. Details of data structures (data types, field names,
etc.)
3. Details of expected inputs
4. Details of validation checks
5. Details of how data is processed
6. Diagrams showing how data moves through the
system
7. Flowcharts describing how the system works

SYSTEM IMPLEMENTATION
The implementation of the new system occurs when
the old system is replaced by the new one.
There are four (4) ways of implementing a new
system. They include:
1. Direct changeover
2. Parallel running
3. Phased implementation
4. Pilot running

DIRECT CHANGEOVER
The old system is stopped completely, and the new system is
started.
Advantages:
1. Takes the minimal time and effort
2. The new system is up and running immediately
Disadvantages:
If the new system fails, there is no back-up system, so data
can be lost.

PARALLEL RUNNING
The new system is started, but the old system is kept
running in parallel (side-by-side) for a while.
Advantages:
1. If anything goes wrong with the new system, the old
system will act as a back-up.
2. The outputs from the old and new systems can be
compared to check that the new system is running
correctly
Disadvantages:
1. Entering data into two systems, and running two systems
together, takes a lot of extra time and effort

PHASED IMPLEMENTATION
The new system is introduced in phases (stages, or steps),
gradually replacing parts of the old system until eventually, the
new system has taken over.
Advantages:
1. Allows users to gradually get used to the new system
2. Staff training can be done in stages
Disadvantages:
1. If a part of the new system fails, there is no back-up system,
so data can be lost

PILOT RUNNING
The new system is first of all piloted (trialed) in one part of the
business / organization (e.g. in just one office, or in just one
department) and thereafter introduced to the all of the business /
organization.
Advantages:
1. All features of the new system can be fully trialled
2. If something goes wrong with the new system, only a small part
of the organization is affected
3. The staff who were part of the pilot scheme can help train other
staff.
Disadvantages:
1. For the office / department doing the pilot, there is no back-up
system if things go wrong

EVALUATION AND MAINTENANCE
The purpose of an evaluation is to assess the system to see if
it does what it was supposed to do, that it is working well, and
that everyone is happy with it.
What Does an Evaluation Look For?
1. Efficiency
2. Easy to use
3. Appropriateness
How is a System Evaluated?
1. Check against the Requirements Specification
2. Check the Users' Responses
What Happens Next?
If any limitations or problems are identified with the new
system, the whole process repeats or maintenance is carried
out on the new system.

EVALUATION
1. What is system analysis?
2. What is system design?
3. Who is a system analyst?
4. What are skills of a system analyst?
5. How do system analysts solve problems?
6. What is a system?
7. What is an information system?
8. What is a subsystem?
9. What are the main components of system
information system?
10. What are four examples of information system?

RESEARCH/PROJECT
1. What are 7 new types of information systems that
cannot be classified as ‘classical’ types of
information systems found in organizations?
2. What is the meaning of SDLC?
3. State the meaning of SDC?
4. State the objectives of SDLC
5. Outline stages in systems development cycle
(SDC) and draw the waterfall system development
cycle diagram.
6. State advantages of SDLC
7. State disadvantages of SDLC
(Reference: see pages 103 to 105 of your textbook)

Systems development cycle

More Related Content

What's hot (20)

Viewers also liked (10)

Similar to Systems development cycle (20)

More from Samuel Igbanogu (15)

Recently uploaded (20)

Systems development cycle