System Analysis Flashcards
Order of creating a new Computer System
- Analysis
- Design
- Development and Testing
- Implementation
- Documentation
- Evaluation
Analysis
- Researching the existing system
- Recording information about the current system
- System Specification
Methods of researching the existing system
- Questionnaires
- Interviews
- Observations
- Examination of existing documents
Questionnaires
Prepared questions are given to users of the system and they are left with the user to complete. They focus on simple questions like yes or no answers.
Advantages of Questionnaires
- Questions are answered quickly
- Fairly cheap to carry out
- Answers are honest because they are annonymous.
Disadvatages of Questionnaires
- People often dont complete or return them.
- You can get incorrect data if they dont understand the question.
- It is hard to ask very technical or specific questions.
Interviews
They take place face to face and usually involve more detailed questions than questionnaires. The interviewer talks with different people at different levels of the business and they might be asked different questions.
Advantages of Interviews
- Questions can be explained if misunderstood.
- Complex questions can be asked.
- You get a full set of data because the person has no choice but to answer all the questions.
Disadvantages of Interviews
- They take more time to complete
- They are more expensive because employees are taken out of their work hours.
- Answers might not be honest because they dont remain annonymous.
Observations
A system analyst sits and watches someone using the current system, this way they can log and make notes about different facts.
Advantages of Observations
- Analyst can see exactly what the system fails in and what it does well.
- Not as expensive because employees arent taken from their work space.
Disadvantages of Observation
- Person being watched might feel uncomfortable and work different than normally.
Looking at the current system’s documentation
The system analyst looks through the paperwork for the current system which contains the information needed to implement the new system.
Paperwork includes technical documentation, payroll systems and list of stock items to be stored in the new system.
Advantages of looking at the current system’s documentation
- It can save time because there are copies of previous analysis.
- You see existing inputs, outputs and processing.
- The analyst can predict the size of the system needed by looking at the amount of data it will need to handle.
Disadvantagges of looking at the current system’s documentation
- Time consuming to look through all the paperwork
- The analyst needs to be paid for the time they spend looking at the documentation.
- Time is wasted if the documentation isnt relevant to the new system.
Recording and analysing information about the current system
- Inputs and outputs need to be identified and process the current system.
- Problems are identified.
- User inforamtion and requirements for the new system are needed.
System Specification
- Need to identify suitable hardware and software for the new system.
Design
Documents, files, forms/inputs, reports/outputs and validation are to be designed.
What to design in design phase
- Designs to solve any problems
- Data capture forms and screen layouts
- Report layouts and screen displays
- Validation routines
- Required data/file structures
Validation checks
- Range check
- Length check
- Character check
- Format check
- Limit check
- Presence check
- Consistency check
- Check digit
Range check
Checks if data is between acceptable values
Length check
Checks if data contains the required number of characters
Character check
Checks that the input data doesnt contain invalid character.
Format check
Checks that data is in a specific format
Limit check
Similar to range check but only one of the limits is checked
Presence check
Checks if data is actually present and hasnt been missed out
Consistency check
Checks if fields correspond with each other
Check digit
Looks at an extra digit calculated from the digits of a number and then put on the end of the number
Verification Checks
- Double entry
2. Visual check
Double Entry
Data is entered twice by two different people. The computer compares the two entries and lets the user know if it finds any differencess.
Visual Check
The person enters data nto the computer carfully comparing what they have entered with the data in the original document.
Developent and Testing
- Testing Designs
- Testing Strategies
- Improvements needed as a result of testing
Testing designs
- Data file structures are created and tested.
- Validation routines are created and tested.
- Input and output methods are created and tested.
Testing Strategies
- Testing each module is made to ensure each one functions correctly on its own.
- Now the system needs to be completely tested (all modules together).
Normal Data
Data is acceptable or valid, having an expected value
Extreme data
Data at the limits of acceptability or validity.
Abnormal Data
Data outside the limits of acceptability or validity.
Live Data
Used to test the system after it has been installed into the customer’s workplace.
It is data that is actually used in the company.
Implementation Methods
- Direct Implementation
- Parallel Running
- Pilot Implementation
- Phased Implementation
Direct Implementation
The old system is stopped overnight and the new system introduced immediately.
Advantages/Disadvantages of Direct Implementation
The benefits are immediate
The method can be disastrous if the new system fails.
Parallel running
The old and new systems are run side by side for a time until everyone gets used to it.
Adv/Dis of parallel running
The staff learns to use it gradually but they are required to run both at the same time.
Pilot Implementation
The system is introduced into part of the company and its performance assesed.
Adv/Dis Pilot Implementation
If the new system fails only one part of the company is affected.
It is more expensive than direct changeover.
Phased Implementation
Initially only part of the new system is introduced. When this proves to work properly the next part is introduced until the old system is fully replaced.
Adv/Dis Phased implementation
You ensure that the system works perfectly but you need to evaluate each phase one by one which is expensive.
Documentation
- User Documentation
2. Technical Documentation
User Documentation
It is designed to help users know how to use the software or system.
- How to log in / out
- How to save files
- How to search
Technical Documentation
It helps programmers and analysts who make improvements to the system or repair and maintain it.
- Input formats
- Program listing and coding
- File structures
- Hardware and software requirements.
- Purpose of the system
Evaluation
It is necssary to do some evaluation and carry out maintainance if necessary.
Evaluation Strategies
- Compare the solution with the original task requirements
- Identify limitations and necessary improvements to the system
- Evaluate the users’ resposes to the results of testing the system
