analysis and design

• When a new computer system is being developed, the main stages of the systems life cycle are: Analysis, Design, Development and testing, Implementation, Documentation, and Evaluation
• Analysis stage


  1. Research to collect data from the current system

  2. Describe the current system (establishing inputs, outputs and processing)

  3. Identify the problems with the current system

  4. Agree the objectives with the clients

  5. Identify and agree customer requirements

  6. Interpret customer requirements

  7. Produce a cost-benefits analysis

  8. Identify suitable hardware and software

  9. Produce a data flow diagram
• Methods of researching the current system

  • Observation
  • Questionnaires
  • Interviews
  • Examination of existing documents
• Interviews are a method of researching the current system
• Drawbacks of using interviews

  • Time consuming
  • Expensive method (by using analyst time)
  • Interviewee can't remain anonymous
• Data Flow Diagram (DFD)


  Helps the analyst by showing the data flows, input and output requirements, processing and type of data storage needed
• Describing the current system

  1. Identify what input and output takes place

  2. Identify what processing is done

  3. Identify the problems with the current system

  4. Identify user and information requirements for the new system
• Example of reserving a seat on a flight


  • Customer makes a flight enquiry
  • Flight details are input by customer
  • Flight schedule checked
  • Flight booking is confirmed
  • E-ticket is issued to customer
• Purpose of DFDs


  • Identify inputs, outputs, processing of the current system
  • Identify problems with the current system
  • Identify user and information requirements for the new system
• System specification


  1. Identify and justify suitable hardware for the new system

  2. Identify and justify new software for the new system

  3. Identify storage requirements (size and type of storage)
• Input devices


  • Barcode readers
  • Scanners
  • Touch screens
• Output devices


  • 3D printer
  • Large monitors
  • Speakers
• Software


  • Operating system
  • Off-the-shelf applications software
• Storage requirements


  • Size of storage
  • Type of storage (hard disk drives, solid-state drives, magnetic tape)
• The next stage after analysis is the design stage
• Design stage


  1. Design the data capture form / input forms

  2. Design the screen layout

  3. Design outputs in the form of screen displays and printed reports

  4. Produce system flowcharts

  5. Design validation rules
• Storage considerations


  • Size of storage (how many bytes of storage are required for the systems to run now, and in the future)
  • Type of storage (which storage type is the most suitable for the company: hard disk drives, solid-state drives or even magnetic tape drives)
  • Data access and data write speeds
  • Number of read-write operations (there is still some doubt about the longevity of SSD if it has to endure large numbers of read-write Operations)
  • Type of access (can it be serial access to the data (all read in order) or does it need to be direct (no need to read all the data in order))
  • If huge amounts of storage are required and data access time is not that Important, magnetic tape may still be the best option
• Design stage


  1. Design file structures and data structures

  2. Design input formats, including data capture forms

  3. Design output formats, including screen layouts and report layouts

  4. Design validation routines
• Basic steps of design

  1. Design the data capture form / input forms

  2. Design the screen layout

  3. Design outputs in the and the printed report form of screen displays

  4. Produce system flowcharts

  5. Design validation rules that need to be used

  6. Design / agree on file structures

  7. Produce any algorithms or program flowchart

  8. Design a testing strategy / plan
• Record


  A unit of data in a file
• Field


  A piece of data within a record
• Primary key field


  A field that uniquely identifies each record
• Data types


  • Alphanumeric
  • Character
  • Text
  • Boolean
  • Numeric (Integer, Decimal/real, Currency, Date/time)
• Validation is not a check on whether the data is correct or accurate; it is only a check to see if it is reasonable
• Validation checks


  • Range
  • Type/character
  • Length
  • Format
  • Presence
  • Check digit
• Verification


  A way of preventing errors when data is copied from one medium to another
• Verification methods


  • Double entry
  • Visual check
• Validation is a method of checking data, verification is a method of preventing errors, and proof-reading is a method of identifying errors
• Data capture forms


  • Ensure data is input into the computer in the correct format
  • Can be paper-based or electronic-based
  • Have clear headings and instructions
  • Use text boxes, tick boxes, and radio buttons
  • Have clear fonts and text styles
  • Provide sufficient space to input data
• Computer-based data capture forms

  • Use text boxes to capture key data clearly
  • Use on-screen help when completing the form
  • Use drop-down/combo boxes where there are limited choices
  • Use radio buttons and tick boxes requiring a single click of a mouse to select
  • Automatically validate data as it is entered
  • Have control buttons (such as next form, clear entry, save, etc.)
  • Have double entry boxes (with verification rules) to check correctness of key data
• Considerations before creating a data entry form

  • Know the type of data which will be captured
  • Know the different tables and their relationships
  • Know the different fields including keys
  • Know the data types for each field (Text, Integer, Boolean, Date & Time, Object)
• Output formats - screen layouts and report layouts

  • Make sure all the output fields are correct
  • Ensure instructions or descriptions are clear
  • Avoid large areas without content
  • Use clear font color and size
  • Output reports should include report type (header, footer, fitting page correctly)
• The following items need to be designed when replacing an existing computer system: inputs to the current system, data capture forms, report layouts, validation routines, file structure