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System Life Cycle


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System Life Cycle

  1. 1. Momina Mateen Chapter 4 – The Systems Life Cycle4.1 systems analysis Analysis Evaluation Design Development and Documentation Testing ImplementationWhat is involved in Systems Analysis?1. Collecting information on how the existing system worksMethods of collecting information include : a. Examination of documents i. This helps the analyst identify the inputs and outputs of the system as it currently operates ii. Assess the processing that the computer system will need to carry out. iii. Calculate the number of documents that are processed iv. Volume of data on all the documents • This would help the analyst decide on the size of memory. b. QuestionnairesWhen using a questionnaire, keep in mind that the way the question is asked can influence the way people answer thequestion. Advantages Disadvantages An effective questionnaire once created They may take a lot of time to produce allows you to give out many copies. Since they are impersonal and anonymous, workers might exaggerate their answers Difficult to ask further questions Not all the employees will actually fill in the questionnaire. Page 1
  2. 2. Momina Mateen c. Interviews • Takes time to complete an interview • This technique is used with key personnel and representatives of the workers. Advantages Disadvantages They are flexible; the interviewer can move It takes a lot of time to organise an interview away from the ‘script’. Interviewees may not give very accurate answers ; they may try to provide the interviewer with answers that they want to hear. It takes a lot of time to complete interviews. d. Observation • This is when a system analyst just watches all the activities that are going on in the office. • For example: seeing how the data comes in about a customer and how it is processed and used to produce an invoice. Advantages Disadvantages The system analyst can see the whole process “Hawthorne Effect”- some people know that they are being watched so they may change the way they work. A data flow diagram can be produced which help determine the inputs, outputs and processing. e. Choice of Method What does it depend on? 1- The type of information that is being collected. 2- The practicality of using the method in the situation Example: If there were lots of employees it would take very long to personally interview each one.2. Establishing inputs, outputs and processing in the existing system  The analyst will use the information that they obtained from examining the documents used in the current system to produce documentation of the system.  This stage is usually done while producing a data flow diagram  Each section of the system is examined to see what specific • Inputs • Outputs • Processing is required Page 2
  3. 3. Momina Mateen3. Recording Information about the Current System “It is important to keep accurate records of systems analysis since the system will continually evolve and other systems analysts and programmers will need to develop the system even further.What are data flow diagrams? • They are a graphical method of recording the inputs, outputs and processing that have been identified.Data flow diagrams 1. The order comes from the customer. The customer is no part of the process so they are placed in the terminator. 2. Data from the customer is the order. This information is processed to produce invoices. They are placed in the process box. 3. Outputs from the system (invoices and printed orders) are recorded for future use. Despite the fact that information is not stored on computers, this process can still be viewed as being stored. This data is called a store. 4. Data flow. These are the arrows. They show the direction of the data flow.For ExampleSystem Flowchart  This is a method that can be used to design system solutions.  It is not frequently found in the analysis stage  A system flowchart is designed to represent a new computerised system. The dataflow diagram represents the old manual system Page 3
  4. 4. Momina Mateen4. Identifying Problems with the Current SystemUse of dataflow diagrams: helps analyst identify problems with the current system. • Weaknesses can be identified. • If you show the process in great detail it will be easier to identify if there are problems like job duplication or time wasting.5. Identifying suitable hardware and software for a new system • Keep in mind that the actual hardware/software is not chosen just yet. • From the data flow diagrams the required outputs, storage and process requirements have been decided. The analyst can then make generalised recommendations for the software/hardware.6. Identifying the user and information requirements“The process of collecting information about the existing system will have been very important to see exactly what jobeach worker is doing.”4.2 Design • The system analyst may involve the use of a programmer.What is a programmer? • The person who will actually write the software (if a new software is to be written).What will need to be designed? • Inputs to the system • Outputs from the system • Files and/or databases needed to store the data • Processing required to produce the outputs • Validation checks that will be needed • Data needed to test the systemDesigning data collection forms and screen layouts • Data collection forms : • hard copy • Screen basedPoints to be taken when designing a data collection form: i. Analyst must make it easy for worker to fill in ii. It must be easy for the secretary to read the information iii. Requirements of completing the form should be clear to workers iv. Design of the forms will depend on the user requirementsMost common method: put boxes in each section that is to be completed . One box for every character of requiredinput.How does this benefit? • Use of boxes – worker is likely to make fewer errors when filling the form • Form will be easier for the secretary to read, so less errors will be made when typing in the errors. Page 4
  5. 5. Momina MateenDesigning an input screen • The number of factors that need to be considered when designing the input screen: × It must be easy to use × It must be attractive to look at × It needs to limit the possibility of inaccurate data being entered × It must contain guidelines for workers on how to fill in any data entry forms × It must also allow them to navigate from one screen to another without difficultyWhat will the input design influence? × It influences the choice of inputDesigning report layouts and screen displays • When these will be designed “the analyst and the programmer will be heavily influenced by the views of the users and what the systems’ analyst has agreed are the users’ requirements.” • Features of the input design must be present on the output design (being attractive and not over-elaborate. • Screen displays must have instructions on how to move from screen to screen.What are the two main aspects of the way output is designed? 1. Format of the output i. Graph ii. Lists of records iii. Reports iv. Tables 2. Medium it is to be produced on i. Paper ii. Screen display iii. SoundWhat about the layout of the documents? • Consider who will see them • Consultation with the owners of the company.What about the screen output? • It must be simple as possibleUsers: secretaries and sales people; they do not have to see the advertisements. • The screen output must not contain any extra material other than that required. • Each output screen must have a consistent theme so the user doesn’t get confused. • Instructions on how the user is to navigate between screens must be included on the screen.Designing the required data/file structures and processing • In theory: steps happen in order • In reality: design of the processing occurs at the same time as designing the files and databases. • To produce a data structure, a systems flowchart has to be produced. The parts of the systems flowchart are broken down into algorithms. Page 5
  6. 6. Momina MateenSo what will the analyst need to do? • He needs to create 2 files. 1. Master file: contains data that doesn’t change often (Name, works number, department, hourly rate, etc) 2. Transaction file: contains data that changes every weekThese two files processed together produce a payroll.How it works? 1. Transaction file is checked for errors 2. It is then sorted in the same order as the master file 3. The transaction file is stored on a magnetic disk (holding data in sequential order)Now the analyst decides on the individual file structure and whether or not programming is required.What things need to be looked at in the master file?Attributes of a master file:  Field names  Field types  Validation rules  Field descriptions  Selection of key fieldDesigning Validation Routines • It must be ensured that the number of errors made is very small. • The number and types of routines depend on the form of input and the file structures that are being used in the system.Keep in mind: All fields cannot have a validation check. For instance, there are so many variations of a person’s name.Types of checks 1. Range check: data containing numeric data 2. Length check: this can be used for text fields 3. Format/Picture check: check if a specific field has a specific format. For instance it must contain 4 numbers followed by a letter. 4. Invalid character check: input is checked in order to ensure that it is digits or all text 5. Check digit: this is when a calculation is performed on a long string of digits which produces an extra digit which is added to the end of the string of digit.Possible Validation ChecksField Name Validation CheckPay Type Must be ‘weekly’ or ‘monthly’Payment Method Must be ‘bank transfer’ or ‘cheque’Works Number Length check: must be 5 characters Format/Picture: must be 4 digits followed by a letter.Department Must be ‘works’ Page 6
  7. 7. Momina MateenTax Code Length Check: >3 and <6 Format/Picture Check: must be 3 or 4 digits followed by ‘L’ or ‘H’NI Number Length check: must be 13 characters Format Check: 2 letters, then a space, 2 digits, a space, 2 digits, space, 2 digits, a space, and then 1 digit.Total Payment Range Check: >=0 or <=1000Other Ways of Reducing Errors 1. Reduce the volume of data. For instance, using coding; using ‘y’ instead of ‘yes’. Less data is entered so fewer errors are made. This also means that there will be simpler and shorter validation routines. 2. Use direct data entry methods. For example barcode reading or optical mark reading.Specifying the required hardware and softwareWhat is the chosen supplier of the hardware based upon? • Cost • Reliability • After-sales support that can be entered.× At this stage the analyst makes general recommendations about the size and type of hardware and the type of software.× “The volume of data will determine the choice of the output devices.”× If it is a heavy volume of data then an inkjet printer would not be suitable. So this means that the order in which the data will be output will affect the choice of storage devices.× The analyst will also need to choose the type of software. The analyst will have to choose from the following: 1. Off-the-shelf software Advantages Disadvantages Cheaper as it is mass produced Difficult to adapt to particular use Available straight away Several distracting features Rigorous testing carried out by developers May not necessarily match up with the existing system and software use. Help lines with operators available Page 7
  8. 8. Momina Mateen 2. Purpose-built softwareAdvantages DisadvantagesDesigned specifically for the task Cost when the programmers have to be paid to write the code for the taskDoes not have to be adapted for use It is only tested by the person who wrote the programProgrammers can make any changes required It is supported limited to the team of programmers Can take a long time to develop.4.3 Development and TestingCreating the System • Once the data structure has been designed, it needs to be created using the software that has been recommended by the systems analyst. • The programmer produces the program code that is needed to solve the problem. • The nature of the problem determines how much programming is required.For example:(Small Company)Main requirement: production of invoices and payslipsSolution: basic database package, spreadsheet package and word processor.Big companies may require a whole brand new software to be written for them.Testing Strategies • It is vital that the analyst makes a test plan.There are two main ways of doing this: 1. Test Data i. Normal Data • This is data that is acceptable. • It should not produce an error when input into the system.Example:In a payslip no-one should have worked more than 65 hours or less than 0 hours. So data that lies within that is enteredand if an error message is produced it means that there is a problem with the system. ii. Extreme Data • Used only when a range of data is input. • Things like name and address will not have any extreme data. • But in the case of a payslip where the most amount of hours worked could be 65 and the lowest could be 0; entering 65 or 0 would be considered as extreme data. iii. Abnormal Data • This is data this not acceptable.For example:You wouldn’t want alphabetic characters in a numeric field. • When data range is used; any number outside that range will be considered as abnormal. • For instance with the payslip; any number that lies outside the range of 0 and 65 hours will be considered as abnormal data. Page 8
  9. 9. Momina MateenTest PlanTest Test Data Expected Results Actual Results CommentInput hours worked -1 Rejected Error message Abnormal Data 65 Accepted Wages Calculated Extreme Data 0 Accepted Wages calculated Extreme Data but the result was 0 40 Accepted Wages calculated Normal Data 140 Rejected Error message Abnormal Data Akhbar Rejected Error message Abnormal Data 2. Live Data • This is data that has been used in the existing system. • It is useful to use it because the outputs of the system are already known.Improvements that could be needed as a result of testing • Before implementation; the system needs to be cleared of any errors that were identified in the testing stage. • This may include altering the validation check. • “Checking the data validation, calculations, and file structures is reasonably straightforward as the test plan will show where there are differences between the expected and the actual results.”What if the output from the system still doesn’t have exactly what is expected when the live data is used? • Single stepping is the solution. This is basically when the software allows you to run the system one step at a time so the exact point where the differences arise can be identified. Page 9
  10. 10. Momina Mateen4.4 ImplementationParallel Running • This is when the new system is run along side the old system. Meaning that the results on the new system can easily be checked against those of the old system.Advantages DisadvantagesWorkers can be trained to use the new system gradually 2 sets of workers need to be paid to keep both the systemswhile it is being implemented running.If the new system fails the old system is always available as It takes a longer time to implement than any other methodthe back up.Direct Changeover • The existing system is replaced by the new one instantly. This method should only be used if the new system has been tested thoroughly. There is a major risk taken here because if the old system is shut down it cannot be reintroduced.Advantages DisadvantagesCost is less than parallel running because only one set If a problem arises there is no back up systemof workers needs to be paid.It is a quick method of implementing the system. It may be difficult to make improvements to the new system and keep it workingPhased Implementation • This is when the new system is introduced to the system one part at a time. This way any problems that arise can be over come and as soon as the system is working fine another aspect can be introduced. This carries on until all aspects have been introduced into the system.Advantages DisadvantagesIf the introduced part of the system fails all the other Slow method of implementation compared toparts are still working direct changeoverWorkers have time to get used to the new system If the new system doesn’t work properly there is no way of going back to the old systemPilot Running • This method is usually taken up by large organisations. The new system is implemented in one of the branches of the organisation while other branches continue with the existing system.Advantages DisadvantagesIf the system doesn’t work; not all the branches are Slow method of implementationaffectedLater branches benefit by learning from the mistakesmade in earlier branches Page 10
  11. 11. Momina Mateen4.5 Documentation• There are two types of documentation: 1. Technical Documentation: produced for systems analysts and programmers. It helps when the system either needs to be further upgraded or developed. 2. User Documentation: helps the users to operate the new system. It could be a tutorial that helps the user through the systemDeveloping elements of technical documentation 1. Systems DocumentationProvides a detailed overview of the whole system.It includes things like: a. Test plans and test results b. Results of the systems analysis; including things like dataflow diagrams c. What is expected of the system d. The overall design decisions; things like choice of hardware and software, file input and output structures. 2. Program Documentation• Produced for the piece of programming code that is written. It includes: a. Description and purpose of the software explaining what the software does, its features, and reasons as to why certain pieces of software were chosen b. The input and output data formats that have been used c. The program flowcharts that were produced at the design stage d. The program listing; copy of the code used with annotations explaining what the code does e. Notes that may help any future programmer to make modifications to the systemDesigning and developing elements of user documentation • This is produced in order to actually help the user use the system.Why does the programmer need to produce this? i. Since the user of the system will not be familiar with the system, they will need help with various parts of the system until they are familiar with it. ii. It will save the analyst time in the long term. They will not have to be contacted on regular basis to show users how to do certain things. What does user documentation include? 1. Screenshots; and how to use the software 2. The purpose of the system 3. Input and output formulas 4. Hardware and software required to run the system 5. Examples of the sample runs of the system 6. What to do when an error occurs 7. Troubleshooting guide or list of FAQ’s Page 11
  12. 12. Momina Mateen4.6 EvaluationThe Set Of Criteria For Evaluation 1. Is the system reliable and robust? 2. Does the system do what it was intended to do? 3. Is the system easy to use? 4. Is the new system efficient? 5. Is the solution appropriate?The Evaluation Process 1. Use the results to evaluate the solution 2. Obtaining feedback from users  Observe the users performing set tasks and their progress using video recording.  A task can be given to the user and the time it takes them to carry out that task can be measured.  Interview the users to gather their responses about what they think of the new system compared to the old one  The analyst could give out questionnaires to the users to judge how easy the new system is to work with compared to the old one. 3. Identifying limitations of the system  Has it met the original objectives?  Is it easy to use?  Have the workers accepted it?  Are there any more requirements? Example o Minor limitation: distracting colours on the user input screen o Major limitation: unable to produce connected output 4. Making improvements to the system  Evaluate the results of testing against the requirement of the specification  Evaluate the results of user testing  The users will be asked about whether they want any improvements in the system  Once the limitations have been decided upon whether or not the good points of the system compensate for the limitations. It will also be decided whether or not the improvements should be included  Once the improvements have been made, the system needs to be developed, tested and evaluated again. Page 12