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Explain about SAP ABAP - Variables?

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Explain about SAP ABAP - Variables?

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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 −

ABAP Dictionary

Reference Variables

The syntax for declaring reference variables is −

DATA <ref> 
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