1. mazharjaved2001@yahoo.com(0333-4461420) Chapter 12 Describing Information Systems

2. mazharjaved2001@yahoo.com(0333-4461420) Describing information systems ► A system is a group of connected operations. ► We can describe them in terms of inputs, processes and outputs ► Systems can be described in several different ways including:  Structure diagrams.  Data flow diagrams.  Systems flowcharts InputProcess Output

3. mazharjaved2001@yahoo.com(0333-4461420) Structure diagrams ► In a structure diagram the overall task is broken down into smaller tasks. ► These smaller tasks can, in turn, be broken down into even smaller tasks. ► This method of describing a task is called ‘The Top Down Approach’. ► It can also be shown as a simple diagram.

4. mazharjaved2001@yahoo.com(0333-4461420) ► First we place the overall task at the top and we write brief description of the overall task. ► This task is then divided up into a series of tasks required to main task. ► Preparing a shopping list ► Do the shopping ► Put the shopping away.

5. mazharjaved2001@yahoo.com(0333-4461420) Example of a ‘Top Down’ structure Make a meal Prepare food Set the table Cook the food The task of making a meal is broken down into smaller tasks –  Preparing the food.  Setting the table.  Cooking the food.

6. mazharjaved2001@yahoo.com(0333-4461420) Example of a ‘Top Down’ structure Make a meal Prepare food Set the table Cook the food Could the smaller tasks be broken down into even smaller tasks?

7. mazharjaved2001@yahoo.com(0333-4461420) Data flow diagrams ► A data-flow diagram shows the logical flows of data through a transaction processing system without regard to the time period when each occurs. ► Physical devices that transform data are not used in these diagrams. ► In a data flow diagram the movement of data around the system is shown. ► This is done using standard symbols including:  Boxes.  Sausages or Circle  Open rectangles.  Arrows.

8. mazharjaved2001@yahoo.com(0333-4461420) Symbols used in Data Flow Diagrams ► A square represents a data source or data destination. Such as an order form from a customer ► A circle (or bubble or Sausage) indicates a process that changes or transforms data. ► An open-ended rectangle represents a store or repository of data. ► A line with an arrow indicates the direction of the flow of data.

9. mazharjaved2001@yahoo.com(0333-4461420) Data flow diagrams A simple data flow diagram that shows a new video being added to a video library

10. mazharjaved2001@yahoo.com(0333-4461420) A Sample Data Flow Diagram Timekeeping Process Payroll Data Employees Payroll Data Paychecks Payroll Data Payroll Details Data Flow Diagram for Payroll Processing

11. mazharjaved2001@yahoo.com(0333-4461420) Systems flowcharts ► A systems flowchart gives an overall view of a system. ► It shows the tasks performed on the data (e.g. sorting, updating) and the type of media used to hold the data (e.g. magnetic disk, magnetic tape). ► Standard symbols are used in systems flowcharts, and data flow is indicated by arrows.

12. mazharjaved2001@yahoo.com(0333-4461420) Systems flowcharts Magnetic tape

13. mazharjaved2001@yahoo.com(0333-4461420) System Flowchart Symbols Input/Output Manual Input Keying Operation Display

14. mazharjaved2001@yahoo.com(0333-4461420) System Flowcharting Symbols Processing Manual Operation Processing Collate Auxiliary Operation Sorting

15. mazharjaved2001@yahoo.com(0333-4461420) System Flowcharting Symbols Storage Punched Card Punched Paper Tape Magnetic Tape Input/Output Document Magnetic Disk Online Storage Offline Storage

16. mazharjaved2001@yahoo.com(0333-4461420) System Flowcharting Symbols Miscellaneous Termination Communication Link Data Preparation

17. mazharjaved2001@yahoo.com(0333-4461420) Systems flowcharts A simple flowchart of a database system

18. mazharjaved2001@yahoo.com(0333-4461420) Flow Charts ► This flow chart shows how an Internet search is conducted.

19. mazharjaved2001@yahoo.com(0333-4461420) System Flow chart for producing gas/electricity bills Sort Program Program producing bills Bills Errors reports OMR reading sheet Validate meter reading sheet Input using keyboard Rejected meter reading Transaction file Sorted payment transaction file Customer master file Updated customer master file Bill file list

20. mazharjaved2001@yahoo.com(0333-4461420) System Flow chart for processing Payroll System Sort Program Update Program Final demandsRemainder Validate Bills posted with cheques or postal orders Payment Transaction file Sorted payment transaction file Updated bill file Bill file list Details of payments direct from banks

21. mazharjaved2001@yahoo.com(0333-4461420)

22. System Flow chart for Payroll Sort Program Update Program Error reports Validate Program Sorted payment transaction file Clock card Error Report Wages Slips Calculates Wages Transaction file Tax tables on disk Employee master file Updated Master file