how do I create a context diagram and a Level 0 DFD:

to prepare and file a tax return with the tax owed to the Internal Revenue Service,

when customer pays check and accounts receivable is updated to reflect the payment and the check is recorded and deposited into the bank,

when customer places online order to purchase merchandise and the order is approved, filled, and sent to the customer with an invoice.

when inventory request is received by the purchasing department and the purchasing department prepares and sends a purchase order to the appropriate vendor.

when vendor invoice is received, reviewed, and compared against the appropriate purchase order, then paid and filed.

when bill of lading for ordered inventory is received from a vendor, recorded, checked against the appropriate purchase order, and filed.