Tables used :
PurchTable and PurchLine : Contains all purchase order headers regardless whether they have been posted or not.
PurchParmTable and PurchParmLine : Contains information regarding posting Purchase headers and Lines.
VendPackingSlipJour and VendPackingSlipTrans : Contains posted packingslip headers and lines.
VendInvoiceJour and VendInvoiceTrans : Contains all invoiced purchase order headers and Lines.
VendReceiptsJour and VendReceiptsTrans : Contains posted receipt header and lines.
VendPurchOrderJour and VendPurchOrderTrans : Contains Purchase requisition headers and lines.
Classes used :
PurchTableType and PurchTableLine classes will get called while creating the PurchaseOrders.
PurchFormLetter_PurchOrder,
PurchFormLetter_ApproveJournal,
PurchFormLetter_Invoice,
PurchFormLetter_PackingSlip,
PurchFormLetter_ReceiptsList
These Classes are used to post the PurchaseOrder at various status (packing, invoice etc).