A transaction in SAP is like a program in normal computer languages, and is identified by a four-character transaction code. A transaction can be initiated directly from the command field on the presentation interface or from the corresponding menu option. There are two kinds of transactions: report and dialog transactions. Report transactions are SAP programs that collect selection parameters from the selection screen followed by the output called the lists. Dialog programs consist of more than one interactive screen called a dynpro. These transactions sometimes also need pre selected information for triggering them, not unlike the explicit selection screens in report programs; these are called parameter transactions.