In contrast with languages like C/C++ or Java, which define a limited set of language-specific statements and provide most functionality via libraries, ABAP contains an extensive body of built-in statements. These statements often support many options, which explains why ABAP programs look "verbose", especially when compared with programs written in C, C++ or Java.
This section lists some of the most important statements in the language, subdivided by function. Both the statements listed here and the subdivision used are fairly arbitrary and by no means exhaustive.
Declarative statements
These statements define data types or declare data objects which are used by the other statements in a program or routine. The collected declarative statements in a program or routine make up its declaration part.
Examples of declarative statements:
TYPES, DATA, CONSTANTS, PARAMETERS, SELECT-OPTIONS, TABLES
Modularization statements
These statements define the processing blocks in an ABAP program.
The modularization statements can be further divided into event statements and defining statements:
Event statements
These are used to define the beginning of event processing blocks. There are no special statements to mark the end of such blocks - they end when the next processing block is introduced.
Examples of event keywords are:
AT SELECTION SCREEN, START-OF-SELECTION, AT USER-COMMAND,
END-OF-SELECTION
Defining statements
These statements delineate callable code units such as subroutines, function modules and methods. The statement marking the end of the unit has the name of the opening statement prefixed with "END".
Examples of defining keywords:
FORM ..... ENDFORM, FUNCTION ... ENDFUNCTION,
MODULE ... ENDMODULE, METHOD ... ENDMETHOD
Control statements
These statements control the flow of the program within a processing block.
Statements controlling conditional execution are:
IF ... ELSEIF ... ELSE ... ENDIF
CASE ... ENDCASE
CHECK
The CHECK statement verifies a condition and exits the current processing block (e.g. loop or subroutine) if the condition is not satisfied.
Several statements exist to define a loop:
DO ... ENDDO
WHILE ... ENDWHILE
LOOP ... ENDLOOP
DO/ENDDO defines an unconditional loop. An exit condition (typically in the form "IF <condition>. EXIT. ENDIF.") must be provided inside the body of the loop. A variant (DO <n> TIMES) sets as exit condition the number of times the loop body is executed. WHILE/ENDWHILE defines a conditional loop. The condition is tested at the beginning of the loop. LOOP/ENDLOOP loops over the lines of an internal table. The loop ends after processing the last line of the internal table.
Call statements
These statements call processing blocks defined using the corresponding modularization statements. The blocks can either be in the same ABAP program or in a different program.
Examples of call keywords:
PERFORM, CALL METHOD, CALL TRANSACTION, CALL SCREEN, SUBMIT,
LEAVE TO transaction
Operational statements
These statements retrieve or modify the contents of variables.
A first group of operational statements assign or change a variable:
MOVE, ADD, SUBTRACT, DIVIDE
These statements, whose syntax originates in COBOL, can be written in a shorter form that uses operators rather than keywords:
MOVE LASTNAME TO RECIPIENT.
* is equivalent to
RECIPIENT = LASTNAME.
ADD TAX TO PRICE.
* is equivalent to
PRICE = PRICE + TAX.
Examples of operational statements on character strings:
SEARCH, REPLACE, CONCATENATE, CONDENSE
Database access statements (Open SQL):
SELECT, INSERT, UPDATE, DELETE, MODIFY
Statements working on internal tables (notice that some "SQL" statements can also be used here):
READ TABLE, INSERT, UPDATE, DELETE, MODIFY, SORT,
DELETE ADJACENT DUPLICATES, APPEND, CLEAR, REFRESH, FREE
Formatting statements
These statements produce or format output. They appear mainly in reports, less so in module pools. Examples are:
WRITE, FORMAT, SKIP, ULINE, MESSAGE, NEW-PAGE
Internal tables in ABAP
Internal tables are an extremely important feature of the ABAP language and merit being explained at some length. An internal table would be defined as a vector of structs in C++ or a vector of objects in Java. The main difference with these languages is that ABAP provides a collection of statements to easily access and manipulate the contents of internal tables. It should be noted that ABAP does not support arrays; the only way to define a multi-element data object is to use an internal table.
