SAP ABAP - Variables | Learn and Master SAP ABAP - Software Development PDF Download

Variables are named data objects used to store values within the allotted memory area of a program. As the name suggests, users can change the content of variables with the help of ABAP statements. Each variable in ABAP has a specific type, which determines the size and layout of the variable's memory; the range of values that can be stored within that memory; and the set of operations that can be applied to the variable.

You must declare all variables before they can be used. The basic form of a variable declaration is −

DATA <f> TYPE <type> VALUE <val>. 

Here <f> specifies the name of a variable. The name of the variable can be up to 30 characters long. <type> specifies the type of variable. Any data type with fully specified technical attributes is known as <type>. The <val> specifies the initial value of the of <f> variable. In case you define an elementary fixed-length variable, the DATA statement automatically populates the value of the variable with the type-specific initial value. Other possible values for <val> can be a literal, constant, or an explicit clause, such as Is INITIAL.

Following are valid examples of variable declarations.

DATA d1(2) TYPE C.  

DATA d2 LIKE d1.  

DATA minimum_value TYPE I VALUE 10. 

In the above code snippet, d1 is a variable of C type, d2 is a variable of d1 type, and minimum_value is a variable of ABAP integer type I.

This chapter will explain various variable types available in ABAP. There are three kinds of variables in ABAP −

• Static Variables
• Reference Variables
• System Variables

Static Variables

• Static variables are declared in subroutines, function modules, and static methods.
• The lifetime is linked to the context of the declaration.
• With ‘CLASS-DATA’ statement, you can declare variables within the classes.
• The ‘PARAMETERS’ statement can be used to declare the elementary data objects that are linked to input fields on a selection screen.
• You can also declare the internal tables that are linked to input fields on a selection screen by using ‘SELECT-OPTIONS’ statement.

Following are the conventions used while naming a variable −

• You cannot use special characters such as "t" and "," to name variables.
• The name of the predefined data objects can’t be changed.
• The name of the variable can’t be the same as any ABAP keyword or clause.
• The name of the variables must convey the meaning of the variable without the need for further comments.
• Hyphens are reserved to represent the components of structures. Therefore, you are supposed to avoid hyphens in variable names.
• The underscore character can be used to separate compound words.

This program shows how to declare a variable using the PARAMETERS statement −

REPORT ZTest123_01. 

PARAMETERS: NAME(10) TYPE C, 

CLASS TYPE I, 

SCORE TYPE P DECIMALS 2, 

CONNECT TYPE MARA-MATNR. 

Here, NAME represents a parameter of 10 characters, CLASS specifies a parameter of integer type with the default size in bytes, SCORE represents a packed type parameter with values up to two decimal places, and CONNECT refers to the MARA-MATNF type of ABAP Dictionary.

The above code produces the following output −

Reference Variables

The syntax for declaring reference variables is −

DATA <ref> TYPE REF TO <type> VALUE IS INITIAL. 

• REF TO addition declares a reference variable ref.
• The specification after REF TO specifies the static type of the reference variable.
• The static type restricts the set of objects to which <ref> can refer.
• The dynamic type of reference variable is the data type or class to which it currently refers.
• The static type is always more general or the same as the dynamic type.
• The TYPE addition is used to create a bound reference type and as a start value, and only IS INITIAL can be specified after the VALUE addition.

Example

CLASS C1 DEFINITION. 

PUBLIC SECTION. 

DATA Bl TYPE I VALUE 1. 

ENDCLASS. DATA: Oref TYPE REF TO C1 , 

Dref1 LIKE REF TO Oref, 

Dref2 TYPE REF TO I . 

CREATE OBJECT Oref. 

GET REFERENCE OF Oref INTO Dref1. 

CREATE DATA Dref2. 

Dref2→* = Dref1→*→Bl.

• In the above code snippet, an object reference Oref and two data reference variables Dref1 and Dref2 are declared.
• Both data reference variables are fully typed and can be dereferenced using the dereferencing operator →* at operand positions.

System Variables

• ABAP system variables are accessible from all ABAP programs.
• These fields are actually filled by the run-time environment.
• The values in these fields indicate the state of the system at any given point of time.
• You can find the complete list of system variables in the SYST table in SAP.
• Individual fields of the SYST structure can be accessed by using either “SYST-” or “SY-”.

Example

REPORT Z_Test123_01. 

WRITE:/'SY-ABCDE', SY-ABCDE,       

      /'SY-DATUM', SY-DATUM, 

      /'SY-DBSYS', SY-DBSYS, 

      /'SY-HOST ', SY-HOST, 

      /'SY-LANGU', SY-LANGU,

      /'SY-MANDT', SY-MANDT,

      /'SY-OPSYS', SY-OPSYS,

      /'SY-SAPRL', SY-SAPRL,

      /'SY-SYSID', SY-SYSID,

      /'SY-TCODE', SY-TCODE,

      /'SY-UNAME', SY-UNAME,

      /'SY-UZEIT', SY-UZEIT.

The above code produces the following output −

SY-ABCDE ABCDEFGHIJKLMNOPQRSTUVWXYZ  

SY-DATUM 12.09.2015 

SY-DBSYS ORACLE                   

SY-HOST sapserver 

SY-LANGU EN 

SY-MANDT 800 

SY-OPSYS Windows NT 

SY-SAPRL 700 

SY-SYSID DMO 

SY-TCODE SE38 

SY-UNAME SAPUSER 

SY-UZEIT 14:25:48