ABAP Programming Language

ABAP supports a hybrid programming model. You can use an object-oriented ("OO") programming model based on classes and interfaces, and you can use the more classic procedural and event-driven programming model based on function modules, subroutines, dialog modules, and event blocks. Both models can be used in parallel. You can use classes inside classic processing blocks or you can call classic procedures from methods. In ABAP Objects, SAP has implemented a cleanup of the ABAP language. Within the scope of this language cleanup, stricter syntax checks are performed in classes that restrict the usage of obsolete language elements.

ABAP (Advanced Business Application Programming) is a programming language for developing applications for the SAP R/3 system,a great business application subsystem. The latest version, ABAP Objects, is object-oriented programming. SAP will run applications written using ABAP/4, the earlier ABAP version, as well as applications using ABAP Objects.ABAP is the symbol for sophisticated technology.

The language is fairly easy to learn for programmers but it is not a tool for direct use by non-programmers. Good programming skills, including knowledge of relational database design and preferably also of object-oriented concepts, are required to create ABAP programs.

ABAP remains the language for creating programs for the client-server R/3 system, which SAP first released in 1992. As computer hardware evolved through the 1990s, more and more of SAP's applications and systems were written in ABAP. By 2001, all but the most basic functions were written in ABAP. In 1999, SAP released an object-oriented extension to ABAP called ABAP Objects, along with R/3 release 4.6.

SAP's most recent development platform, NetWeaver, supports both ABAP and Java.

SAP basis

SAP Basis is the technological platform that supports the entire range of
SAP applications, now typically implemented in the framework of the
SAP Web Application Server. In that sense SAP Basis can be seen as
the "operating system" on which SAP applications run. Like any operating
system, SAP Basis contains both low-level services (for example memory
management, database communication or servicing Web requests) and
high-level tools for end users and administrators. These tools can be
executables ("SAP kernel") running directly on the underlying operating
system, transactions developed in ABAP, or Web-based interfaces.

It can also provides a layer of abstraction between the business applications and the operating system and database. This ensures that applications do not depend directly upon a specific server or database platform and can easily be ported from one platform to another.

Transactions The normal way of executing ABAP code in the SAP system is by entering a transaction code. Transactions can be accessed via system-defined or user-specific, role-based menus. They can also be started by entering their transaction code (a mnemonic name of up to 20 characters) in the special command field, which is present in every SAP screen. Transactions can also be invoked programmatically by means of the ABAP statements CALL TRANSACTION and LEAVE TO TRANSACTION. Transaction codes can also be linked to screen elements or menu entries. Selecting such an element will start the transaction. The term "transaction" must not be misunderstood here: in the context just described, a transaction simply means calling and executing an ABAP program. In application programming, "transaction" often refers to an indivisible operation on data, which is either committed as a whole or undone (rolled back) as a whole. This concept exists in SAP but is there called a LUW .

there are various types of transactions...............

Dialog transaction

These are the most common kind of transactions. The transaction code of a dialog transaction is linked to a Dynpro of an ABAP program. When the transaction is called, the respective program is loaded and the Dynpro is called. Therefore, a dialog transaction calls a Dynpro sequence rather than a program. Only during the execution of the Dynpro flow logic are the dialog modules of the ABAP program itself are called. The program flow can differ from execution to execution. You can even assign different dialog transaction codes to one program.

Parameter transaction In the definition of a parameter transaction code, a dialog transaction is linked with parameters. When you call a parameter transaction, the input fields of the initial Dynpro screen of the dialog transaction are filled with parameters. The display of the initial screen can be inhibited by specifying all mandatory input fields as parameters of the transaction.

Variant transaction In the definition of a variant transaction code, a dialog transaction is linked with a transaction variant. When a variant transaction is accessed, the dialog transaction is called and executed with the transaction variant. In transaction variants, you can assign default values to the input fields on several Dynpro screens in a transaction, change the attributes of screen elements, and hide entire screens. Transaction variants are maintained in transaction SHD0.

Report transaction A report transaction is the transaction code wrapping for starting the reporting process. The transaction code of a report transaction must be linked with the selection screen of an executable program. When you execute a report transaction, the runtime environment internally executes the ABAP statement SUBMIT—more to come on that.

OO transaction A new kind of transaction as of release 6.10. The transaction code of an OO transaction is linked with a method of a local or global class. When the transaction is called, the corresponding program is loaded, for instance methods an object of the class is generated and the method is executed.