Consider the following case study for estate agency .Draw level-0 data flow diagram. Clients wishing to put their property on the market visit the estate agent, who will take details of their house, flat or bungalow and enter them on a card, which is filed according to the area, price range and type of property. Potential buyers complete a similar type of card, which is filed by buyer name. Weekly, the estate agent matches the potential buyer' requirements with the available properties and sends them the details of selected properties. When a sale is completed, the buyer confirms that the contracts have been exchanged, client details are removed from the property file, and an invoice is sent to the client. The client receives the top copy of a three-part set, with the other two copies being filed. On receipt of the payment, the invoice copies are stamped and archived. Invoices are checked on a monthly basis and for those accounts not settled within two months a reminder (the third copy of the invoice) is sent to the client.

Consider the following case study for estate agency .Draw level-0 data flow diagram. Clients wishing to put their property on the market visit the estate agent, who will take details of their house, flat or bungalow and enter them on a card, which is filed according to the area, price range and type of property. Potential buyers complete a similar type of card, which is filed by buyer name. Weekly, the estate agent matches the potential buyer' requirements with the available properties and sends them the details of selected properties. When a sale is completed, the buyer confirms that the contracts have been exchanged, client details are removed from the property file, and an invoice is sent to the client. The client receives the top copy of a three-part set, with the other two copies being filed. On receipt of the payment, the invoice copies are stamped and archived. Invoices are checked on a monthly basis and for those accounts not settled within two months a reminder (the third copy of the invoice) is sent to the client.