SYSTEMS ANALYSISCHAPTER 8 P 94 TO P

101IGCSE ICT 0417

Systems Analysis

Definition of a system Stages of system Analysis:

Analysis Design Development and Testing Implementation Documentation Evaluation

What is a system?

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…

Analysis Stage (feasibility study)

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:

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

Design Stage

This stage consists of designing the key parts or elements of the recommended system: This might include: Data capture forms/input forms, screen

layouts Output forms and reports System flowcharts and pseudo code Validation rules data verification methods

Data Verification

Verification is way of preventing errors when data is copied from one medium to another: There are two ways verification checks are carried out: 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).

Data Validation

The is a process where data is checked to see if it satisfies a certain criteria when input into the computer. Validation techniques:

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

Check Digit ExplanationExample: Barcode

51043112017

51043112017

51043112017

Bar Code

Odd Digits

Even Digits

5+0+3+1+0+7 = 16

1+4+1+2+1=9

16x3 = 48

Odd digits X3

+ 9Even Digits

=57What is the number needed to make 57 a

multiple of 10?That is the check digit In this case it is 3!!!

3

Development and Testing

Once the system is designed, it is then necessary to make the system (develop) and fully test it:

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.

Development and Testing

Testing of each module of the system needs to be done thoroughly in order to ensure proper functioning of the system.

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.

ImplementationOnce 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.

DocumentationThere are two types of documentation in any system: user and technicalUser 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 packagehow to log in/log outhow to load/run the softwarehow to save fileshow to search for informationhow to sort datahow to printhow to add, delete or amend recordsscreen layouts (input)print layouts (output)hardware requirementssoftware requirementssample runs (with test data and results)Error handling/meaning of errorstroubleshooting guide/help FAQstutorials

Documentation Cnt’dTechnical 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 packageProgram listing/codingProgramming language usedFlowchart/algorithmInput formatsHardware requirementsSoftware requirementsMinimum memory requirementsKnown bugs in the systemList of variables used and their meaning or descriptionFiles structuresSample runs (with test data and results)Output formatsValidation rulesMeaning of error messages

EvaluationSystem 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 requirementIdentify any limitations in the systemIdentify any necessary improvements that need to be madeEvaluate the user’s responses to using the new systemCompare test results from the new system with results from the old systemCompare the performance of the new system with that of the old oneObserve users performing set tasks, comparing with old systemMeasure the time taken to complete the set tasks, comparing it with old systemInterview users to gather responses about how well the system worksGive out questionnaires to gather responses about the ease of use of the new system

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