ABAP/4 is the language created by SAP AG for implementation and customization of their R/3 system.

The rough English translation of the acronym would be A Business Application Programming language, version 4.

It is a block-structured language that seems to me to most resemble a cross between Oracle's PL/SQL and IBM's PL/I.

• It contains a moderately rich set of data structures; integers, ``packed'' BCD numbers, character strings, dates, times, ...

 
• Some reasonable modularization tools handling both subroutines that are localized (called a FORM), and globally defined encapsulated functions (called FUNCTION MODULES).

 
• A somewhat weak set of SQL operators; a select statement is represented by a loop structure, where operations are placed within the loop. e.g. A typical selection would look like:

select * from mytable where key like '25%'.         write: / mytable-key, mytable-value.         perform do_something using mytable-value.     endselect.

The operators are somewhat ``weak'' in that they cannot be directly composed to generate such things as inner or outer joins; one would instead nest select ``loops'' one within another.
 
• ABAP/4 contains some highly report-oriented event-driven control structures. For instance, events can be defined for:

 
• INITIALIZATION.

 
• START-OF-SELECTION.

 
• END-OF-SELECTION.

 
• AT NEW-PAGE.

 
• AT END-OF-PAGE.

 
Reports can be defined with drill-down capabilities, where by ``double-clicking'' on a line on a report, the program may be requested to display a "subreport," or perhaps to run an independent report or transaction.

There are also events defined to automate access to ``logical databases,'' that is, to selectively walk down a hierarchy tree defined for a set of related tables. This can be used to provide (without programmer intervention) additional selection and sort criteria as parameters to reports.
 

• ABAP/4 is a byte-compiled language. The virtual machine is fairly well hidden from view, but core dumps can be examined, and appear to resemble IBM 370 assembly language.

 
• Operations that work on tables will have to access the database server; for efficiency's sake, there is the notion of an ``Internal Table,'' which is an array structure that is stored ``locally'' on the application server . Using internal tables decreases both the load on the network and on the database server, and is highly encouraged, at least for moderate quantities of data.

 
• Some additional ``little languages'' are used to link ABAP/4 code to screen definitions and screen control code to help define online transactions.

 
• Jointly with the ``screen control'' language, ABAP/4 is used to implement substantially all of the visible R/3 system functionality. The R/3 "kernel" represents some (albeit fairly large) programs written in C that interpret ABAP/4 bytecode. There is so much infrastructure built up around this that most users and indeed many developers are probably not aware of where or what the kernel is.