Syllabus Detail

  • Context diagrams Yourdon/DeMarco. 11ATAR,  12 GEN, 12 ATAR
  • Data flow diagrams (DFD) Yourdon/DeMarco 11 ATAR, 12 ATAR
  • System manuals 12 ATAR
  • User manuals 12 ATAR



  • Documentation is essential for any information system and / or product
  • Some documentation helps developers and designers to understand the ins and outs of the system or project, as well as a an integral part of planning
  • Other documentation is created specifically to help the end-user operate the system 


Context Diagrams (Yourdon/DeMarco)

  • A system context diagram, or context diagram, is a diagram used to show the high-level processes of a system
  • These processes are shown along with how they interact with external entities
  • Data is shown as to be "flowing" between the system and external entities, as depicted with arrows
  • Context diagrams are a step before Level-0 DFDs (data flow diagrams) and use similar symbols
    • process is represented with a circle
    • An external entity is represented with a rectangle
    • data store is represented with two parallel lines
    • data flow is represented with a straight line and arrow head in the direction of the flow
  • Context diagrams only show essential general processes without breaking down each step


Data Flow Diagrams (Yourdon/DeMarco)

  • A data flow diagram is also known as a DFD
  • It's the next level up from a context diagram, where we look at each process and break it up further in easy-to-read data flows
  • These data flows are how the system interacts with external entities, as well as databases
  • The processes are numbered with decimals, meaning the first process will have sub-processes in a DFD numbered as "1.1", "1.2" etc.
  • Data flow diagrams use the same symbols as a context diagram
  • Refer to the section "For you to do" below, number 2, for more on DFDs.






 System Manuals (12 ATAR only)

  • System manuals can also be referred to as internal documentation
  • Internal documentation refers to notes and instructions within projects, often seen only by developers
  • This includes comments within the source codes of a project
  • System manuals are generally created for developers and people within the project


User Manuals (12 ATAR only)

  • User manuals can also be referred to as external documentation
  • External documentation is any form of manual or guide used to instruct the end-user of a system
  • User manuals are generally created for end-users in order to educate them on how to use the system


Further Research

  1. Create online diagrams here  OR just do sketches by hand.
  2. Learn how to create context diagrams and data flow diagrams here
  3. Learn about Data Flow Diagrams from this Wiki 'Structured Analysis'


For you to do!

1. What does DFD stand for? What is the purpose of a DFD?

2. How is a process represented? Does it start with a verb or noun?

3. How is an external entity represented? Does it start with a verb or noun?

4. What is an entity?

5. How is a data store represented? What is it?

6. What is a context diagram?

7. What does a data flow look like?


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