Draw a Context Diagram & Level-0 Diagram

The Mail Order Company Plc. The sales order processing system at the Mail Order Company Plc. works as follows:

As orders are received from customers by order clerks they are checked and validated to ensure that all the relevant information has been completed on the order form. If the order is incomplete then the customer is informed by post and the invalid order is not taken any further in the process. However, if an order is valid, then the customer file containing customer number, customer name, address, telephone number, credit limit etc. is checked to see if the customer is an existing customer or a new customer. If the order is from a new customer, then his/her details are added to the customer file.

Next, the stock file containing item number, item name, unit price, number in stock etc. is then checked to ensure that the items on the order are in stock. If the items are not in stock, then the customer is informed and the order placed on a pending order file which contains information such as customer number, order number and expiry date.

If the items are in stock, then the valid order is sent to the accounts department where it is priced with reference to the price file. The customer file is also checked to ensure that the order will not take the customer over his/her credit limit. If it does, then the customer is informed of this. Details of the amount outstanding and of the order itself are placed in the pending orders file. Where no problems are encountered, the customer and stock files are updated with respect to the order details. A dispatch note is prepared and sent to the warehouse.

At the end of each week, order clerks check the pending orders file against the customer file to see if any order should now be processed. If any orders are to be processed, customers are notified. The stock file is also updated to take account of deliveries from suppliers.