Transcript System Life Cycle

ICT Class
System Life Cycle
Large systems development projects may involve
dozens of people working over several months or
even years, so they cannot be allowed to proceed in
a haphazard fashion.
 The goals of an information system must be
thoroughly understood and formal procedures and
methods applied to ensure that the project is
delivered on time and to the required specification.
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There are several versions of the systems life cycle
diagram; the stages include problems definitions,
problem investigation, feasibility study, analysis,
design, Most of all the diagrams are by 5 or 6
steps.
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The course of developmental changes
through which a system passes from its
conception to the termination of its use and
subsequent salvage, it has 6 steps which
are feasibility study, analysis, design,
programming, installation and
maintenance.
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The systems life cycle
approach to development is
also known as the
“waterfall model”. The
waterfall model is a
software development
model describing the naive
approach to software
development in which
development is seen as
flowing steadily through the
phases of requirements
analysis, design,
implementation, integration
and maintenance
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The development of a new information system is a
major undertaking and not one to be undertaken
lightly. For examples stores like Wal-Mart or
Target, they have a computerized distribution
system in the 80’s, business must adapt to remain
competitive. Some of the reasons for introducing
this new system may be:
1. The current system may be no longer suitable
for its purpose
2. Technological developments may have made the
current system redundant or outdated.
3. The current system may be too inflexible or
expensive to maintain.
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Feasibility Study is the
first stage of the
systems life cycle. The
aim of feasibility study
is to understand the
problem and to
determine whether it is
worth proceeding. It
has 5 main factors that
are technical
feasibility, economic
feasibility, legal
feasibility, operational
feasibility and schedule
feasibility.
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Investigating what are we doing now
Fact finding methods
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Questionnaires
Interviews
Observation
Examining documents
Dataflow diagrams
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System Design
The design
specifies the
following aspects of
a system:
The hardware, the
outputs, the inputs,
the user interface,
the test strategy,
conversion plan,
etc.
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The system specification must describe how
the new system will work. Screen layouts and
report formats must be designed, file
contents and organizations specified, and
each program in the system must be
described by means of programs
specifications, structure charts, pseudo code
or flowcharts
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Prototyping is considered as a
strategy in system
development in which a scaled
down system or portion of a
system is constructed in a
short time, tested, and
improved in several iterations.
A prototype is an initial version
of a system that is quickly
developed to test the
effectiveness of the overall
design being used to solve a
particular problem.
Prototyping is similar to the
Evolutionary (Iterative) Design
Process. It is sometimes
termed rapid prototyping and
is similar to rapid application
development (RAD).
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The use of structure charts and
pseudo codes for describing
algorithms. Algorithm is a sequence
of instruction to solve a given
problem. Pseudo codes is an
intermediate stage between plain
English and the programming
language in which the solution will
eventually be coded.
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Maintainability: The ease with
which a software system or
component can be modified to
correct faults, improve
performance or other
attributes, or adapt to a
changed environment
Usability: will the users find
the system easy to use, will it
save them time, cut out
tedious repetitive tasks, give
them quick access to
information they need.
Suitability: it integrates an
existing software with manual
methods that are adapted to a
new system
Maintainability: it makes
modifications when is required
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Unit Testing: The type of testing where a developer
(usually the
one who wrote the code) proves that a code
module (the "unit")
meets its requirements.
Integration Testing: A type of testing in which
software and/or hardware components are
combined and tested to confirm that
they interact according to their requirements.
Integration
testing can continue progressively until the entire
system has
been integrated.
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There are different types of
maintenance.
Perfective maintenance: this
implies that while the
system runs satisfactorily,
there is still room for
improvement.
Adaptive maintenance: all
systems will need to adapt
to changing need within a
company.
Corrective maintenance:
problems frequently surface
after a system has been in
use for a short time,
however it is thoroughly
tested.
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1. What is the System Life Cycle?
2. List and shortly describe the five main SLC stages.
3. List the contents of a feasibility report
4. List four fact finding methods
5. What is a data flow diagram?
6. Draw and describe the use of four DFD symbols.
7. Describe three alternative solutions in the design stage
8. List the details of the design specification
9. Describe the two types of documentation
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GCSE ICT 4th Edition
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