systems development cycle
TRANSCRIPT
SYSTEM DEVELOPMENT CYCLE
Tuesday, May 2, 2023
LEARNING OUTCOMESAt the end of the lesson, I should be able to:a) -Define system development cycleb) -Describe system development cyclec) -Describe subsystems d) -Draw a system development e) -Stages in system development life cyclef) -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 problems2. Always wanting the improvement of the
system3. Information technology (IT) knowledge
and programming expertise4. Ability to find facts about the problem
and develop how it should be solved5. Use logical methods to solving problems6. People management knowledge and
skills
THE CONCEPT OF SYSTEMSA 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/Information3. Procedures/Policies4. People5. Communication Networks
TYPES OF INFORMATION SYSTEMS:
1. Transaction processing systems2. Management information systems3. Decision support systems4. 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 system3. Development and Testing - Create the new
system and test it4. Implementation - Place the new system into
the company5. 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 system3. 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. Questionnaires2. Interviews3. Observing people using the current
system4. Looking at the current system's
documentation
DESIGNThis 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.
VALIDATION CHECKS
DESIGNING SYSTEM VERIFICATION
Verification is a way of making sure that data being entered into the system exactly matches the source of the data.
VERIFICATION CHECKS
DEVELOPMENT & TESTINGSystem 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 data2. Create validation rules to make sure that data entered is sensible3. Create a user-interface to allow data to be entered into the system4. Create output formats (reports, pay slip's, bills etc.)
TESTING THE SYSTEMA 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 testedii. The test data to useiii. 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 DATAWhen 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 VALUESExtreme 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 VALUESThis 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 DOCUMENTATIONThere are two types of documentation that should be produced when creating a new system:1. User documentation2. Technical documentation
USER DOCUMENTATIONUser documentation usually includes:
1. List of minimum hardware and software required to use the system
2. How to install the system3. How to start / stop the system4. How to use the features of the system5. Screenshots showing the system in typical use6. Example inputs and outputs7. Explanations of any error messages that
might be shown8. A troubleshooting guide
TECHNICAL DOCUMENTATIONTechnical 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 inputs4. Details of validation checks5. Details of how data is processed6. Diagrams showing how data moves through
the system7. 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 running3. Phased implementation4. Pilot running
DIRECT CHANGEOVERThe old system is stopped completely, and the new system is started.
Advantages:1. Takes the minimal time and effort2. 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 RUNNINGThe 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:3. Entering data into two systems, and running two
systems together, takes a lot of extra time and effort
PHASED IMPLEMENTATIONThe 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
system2. Staff training can be done in stagesDisadvantages:3. If a part of the new system fails, there is no back-up
system, so data can be lost
PILOT RUNNINGThe 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 trialled2. If something goes wrong with the new system, only a
small part of the organization is affected3. The staff who were part of the pilot scheme can help
train other staff.Disadvantages:4. 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. Efficiency2. Easy to use3. Appropriateness How is a System Evaluated?4. Check against the Requirements Specification5. Check the Users' ResponsesWhat 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.
EVALUATION1. 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/PROJECT1. 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 SDLC5. Outline stages in systems development cycle
(SDC) and draw the waterfall system development cycle diagram.
6. State advantages of SDLC7. State disadvantages of SDLC
(Reference: see pages 103 to 105 of your textbook)
END OF NOTE
PLEASE RETIRE
