1. Data Flow Diagrams
CP1
Computing

2. Data Flow Data flow is the way data moves through a computer system.
A data flow diagram is an easy-to-understand way of showing the data flow in a computer system.
A data flow diagram only uses four different symbols…
Computing

3. Process A process is a task to be done.
Eg. Making a holiday reservation, taking out a library book, registering as a guest in a hotel…
Computing

4. External Entity The source or destination of data.
Eg. A holiday-maker, a library member, a hotel guest.
Computing

5. Data store
A place where data is stored.
Eg. A database
Computing

6. Data flow
Shows the direction of the flow of the data between other symbols.
Data flow lines should be labelled with a description of the data.
Computing

7. Example
Where does the data come from that is needed for this process?
First, identify the processes – there is only one here…
The database is searched and room availability is returned.
Add the Data Flow line
Availability data is returned to the guest.
Date, Type of Room
Date, Type of Room
Hotel database
Hotel Guest
Make a Room Enquiry
Availability
Availability
A hotel guest makes an enquiry at a hotel whether a room is available on a certain date. The hotel database is searched and the guest is then told which rooms are available.
Computing