Compared with .Net programming technique, SAP ABAP is mainly the business focused. From the point view of information system technology, SAP ABAP mainly is the language to develop the distributed multiple-tier SAP information systems.
frone tier:
SAP installed SAPGUI distributed SAP client software in different desktops. Software integrated client licenses and presentation logic into user desktop. Presentation logic included components to connect to the middle tier of Netwaver AS Web aplication server.
middle tier:
SAP Netweaver web application server is the middle tier of SAP system. It is the database based server to host all application logics of SAP system. ABAP programming mainly is using this application server to send user requests from client desktop to application server, to get responses from this application server back to the user desktop, and to process the requests and responses with various back-end database servers of SAP system such as MAXDB, SQL Server, ORacle, and DB2, etc.
backend tier:
SAP has a built-in database called MAXDB which can be used to store all ABAP programming codes and persistent data. When we create a simple ABAP program, we store codes in this database. When we run this simple program, SAP copied the codes into memory area and run it for you. If the program is not used anymore in the memory, the codes can be discarded automatically based on the SAP special garbage collection mechanism.
SAP ABAP uses its own syntax to build up the programs. Now the syntax is OO based. SAP successfully integrated ABAP basic syntax into OO technique and have had a brand new ABAP programming technique called ABAP Objects.
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