Data flow diagram

The order is entered in the sales order processing system.  The price of the video and length of rental will be looked up from the stock file. An invoice is printed and given to the customer along with the video just so they know how long they have it for and what the price is.  This is just a bit of evidence so they don’t get overcharged or undercharged.  Details of the sales are stored in the sales file so he can see what is happening with the sales of each and every one of his various types of videos.

At the end of each month the accounts department prints statements to send to all member and customers.  A report of overdue videos is kept in the accounts department and one copy is also sent to the customer obtaining the video.

Below is a table with all of the processes, inputs and outputs that I have based my data flow diagram on.