IGCSE ICT 0417
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Definition of a system
Stages of system Analysis:
Analysis
 Design
 Development and Testing
 Implementation
 Documentation
 Evaluation
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A system is a group of elements which work
together to perform a task.
Example: Nervous system, Respiratory system,
Air Navigation System, Road System,
Computer System etc…
During this stage, analysis of the current system or the new one to be
implemented takes place. This includes some or all of the following:
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Collect data about the current system (observation,
questionnaires, interviews, looking at existing paper
work)
Establish inputs, outputs and processing
Identify the problems with the current system
Make sure the customer agrees with the set objectives
Identifying and interpreting customer requirements
Produce cost benefit analysis
Produce data flow diagram
This stage consists of designing the key parts or elements
of the recommended system: This might include:
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Data capture forms/input forms, screen
layouts
Output forms and reports
System flowcharts and pseudo code
Validation rules data verification methods
Verification is way of preventing errors when data is
copied from one medium to another: There are two ways
verification checks are carried out:
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Double entry: data is entered twice by two
different people. The computer compares the
two entries and identifies any differences.
Visual check: Checking for errors by comparing
entered data on the screen with the data in the
original documents (not proof reading).
The is a process where data is checked to see if it satisfies a certain criteria
when input into the computer. Validation techniques:
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Range check  Checks if data is within given or acceptable
values. (Grade 1 to 7)
Length Check  Does input include required number of
characters. (phone 10 chars)
Character/type check: Contains valid characters only like
phone number should not contain letters.
Format/Picture check: Data must be in a specific format.
Limit Check: Only one boundary is checked
Presence check: Checks that data exists and it is not left out.
Consistency checks: checks if fields tie up together. IF
gender is male title can not be Mrs.
Check digit: Checks that the entered digits are correct
Odd Digits 51043112017 5+0+3+1+0+7 = 16
Bar Code 51043112017 3
Even Digits 51043112017
Odd digits X3
16x3 = 48
+
1+4+1+2+1=9
Even Digits
9
= 57
What is the number needed to make 57 a multiple of 10?
That is the check digit  In this case it is 3!!!
Once the system is designed, it is then necessary to make the
system (develop) and fully test it:
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If the system is a database, all the table, fields, and data types must be
finalised including key field (primary key) for every table.
After the structure is ready, it should be made in to a database
application (like access)
Certain rules of validation and verification (discussed earlier) must be
adhered to. They should be used to trap data errors. Data is being
moved or copied from paper based to an electronic one.
The user interface will also have to be finalized in this stage. This also
includes various input/output/storage devices. (retina scanner,
finger print scanner, printer(inkjet or laser). How about people with
disabilities.
All of these will be finalised to ensure accurate output is produced
with input from the various devices.
Testing of each module of the system needs to be done
thoroughly in order to ensure proper functioning of the
system.
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Testing might force the developer to redesign some parts of the
system.
The data is tested in three different categories:
Normal or acceptable data. Ex: Month can be between 1 and 12
 Extreme or the extreme limits of capacity or validity of data. Ex: In the month 1
and 12 are extreme test cases.
 Abnormal or data which is outside the range of the acceptable or valid. Ex:
Month 0, 13 or month 3.5, month a, or month h4.
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Once the system is fully tested, we should be implementing it or putting it to work with
real data and real people.
Changeover method
Description
Advantages and disadvantages
Direct
Old system out and new system in
+ Benefits are immediate
+ Costs are reduced
+ Less likelihood of malfunction
- Disastrous if nee system fails.
Parallel Running
Old and new system are working
together side by side
+ If new fails, old one is still operating
+ Possible to train staff gradually
+ Staff have time to get used to new
system
- It is more expensive
Pilot implementation
New system is introduced into one
part of the company at a time
+ If new system fails, only that section
gets affected. Direct
+ Possible to train staff in one area
only.
+ Costs less than parallel running
- Costs more than direct changeover
Phased implementation
Introduce the system one part at a time
until full implementation.
+ If a part fails, it is only necessary to
go back to that part or section
+ Possible to ensure system is working
before expanding
- More expensive than direct
changeover since there is need to
evaluate each phase before moving on.
There are two types of documentation in any system: user and technical
User documentation is designed to help users to learn how to use the software or system. Examples of
user documentation are:
 The purpose of the system/program/software package
 how to log in/log out
 how to load/run the software
 how to save files
 how to search for information
 how to sort data
 how to print
 how to add, delete or amend records
 screen layouts (input)
 print layouts (output)
 hardware requirements
 software requirements
 sample runs (with test data and results)
 Error handling/meaning of errors
 troubleshooting guide/help FAQs
 tutorials
Technical documentation is designed to help programmers and analysts who need to make
improvements to the system or repair/maintain it. Examples of technical documentation are:
 purpose of the system/program/software package
 Program listing/coding
 Programming language used
 Flowchart/algorithm
 Input formats
 Hardware requirements
 Software requirements
 Minimum memory requirements
 Known bugs in the system
 List of variables used and their meaning or description
 Files structures
 Sample runs (with test data and results)
 Output formats
 Validation rules
 Meaning of error messages
System evaluation is the last stage of systems analysis where the whole system is evaluated and any
fixing or maintenance is carried out. The following is a list of things considered when evaluating the
system:
 Compare the final solution with the original requirement
 Identify any limitations in the system
 Identify any necessary improvements that need to be made
 Evaluate the user’s responses to using the new system
 Compare test results from the new system with results from the old system
 Compare the performance of the new system with that of the old one
 Observe users performing set tasks, comparing with old system
 Measure the time taken to complete the set tasks, comparing it with old system
 Interview users to gather responses about how well the system works
 Give out questionnaires to gather responses about the ease of use of the new system
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Some result from the above evaluations might require changes to hardware or software:
 Hardware:
 Feedback from end users
 New hardware comes to the market, making change necessary
 Changes within the company which require new devices to be added.
 Software:
 Feedback from end users
 Changes to company structure or how the company works
 Changes in legislation