JULY 11

 I learned about defining modifiable data objects using "DATA" Statement and "PARAMETER" statement and implementing it using programs.

 Variables(modifiable data object)

Two statements are commonly used to define variables in an ABAP/4 program:

·         data

·         parameters

Data Statement to Define Variables

Using data statement, variables can be declared for the program. Variables defined in the data statement are assigned to a data type and can also have defaults.

Syntax for the data Statement

data v1 [(l)] [type t] [decimals d] [value 'xxx'].

or

data v1 like v2 [value 'xxx'].

where:

·         v1 is the variable name.

·         v2 is the name of a variable previously defined in the program, or is the name of a field that belongs to a table or structure in the Data Dictionary.

·         (l) is the internal length specification.

·         t is the data type.

·         d is the number of decimal places (used only with type p).

·         'xxx' is a literal that supplies a default value.

 

Examples of Variables Defined with the DATA Statement 

data f1(2) type c.

data f2 like f1.

data max_value type i value 100.

data cur_date type d value '19980211'.

NOTE: Variable names can be 1 to 30 characters long. They can contain any characters except 

( ) + . , : and must contain at least one alphabetic character. SAP recommends that variable names should always begin with a character and they should not contain a dash. A dash has special meaning. Instead of a dash, we should use an underscore ( _ ).

The following points also apply to the data statement:

·         The default length depends on the data type.

·         The default data type is c (character).

·         The default initial value is 0, except for data type c, which is blank.

·         The value addition only accepts a literal or constant; we cannot use a variable to supply a default value.

·         When using the like addition, the variable being defined obtains its length and data type from the referenced variable. We cannot specify them on the same statement with like. 

·         When using the like addition, the value is not obtained from the referenced variable. we can specify the value addition to give the variable a default value. If we do not, it is assigned a default initial value of 0 (or blank for a character data type).

The data statement can appear anywhere in a program. The definition for a variable must physically come before the statements that access it. If we place a data statement after executable code, the statements above it cannot access the variables it defines.

Example of a Variable That Is Incorrectly Accessed Before It Is Defined

report zprogram.
data f1(2) value 'Hi'.
write: f1, f2.
data f2(5) value 'there'.

The variable F2 is defined on line 4, and the write statement on line 3 is trying to access it. This will generate a syntax error. The data statement on line four should be moved before line 3.

Parameters Statement to Define Variables

A parameter is a special type of variable that is defined using the parameters statement. parameters is a lot like the data statement, but when we run the program, the system will display the parameters as input fields on a selection screen before the program actually begins to execute. The user can enter or modify their values and then press the Execute button to begin program execution. we can use both parameters and data in the same program. The rules for parameter names are the same as for variable names, except for the following:

• The maximum length is 8 characters instead of 30.

• In addition to literals and constants, you can also use a variable to supply default a default value.

Syntax for the parameters Statement

parameters p1[(l)] [type t] [decimals d] ...

or

parameters p1 like v1 ...

... [default 'xxx'] [obligatory] [lower case] [as checkbox] [radiobutton

    group g].

where:

• p1 is the parameter name.

• v1 is the name of a previously defined variable or parameter, or is the name of a field that belongs to a table or structure in the Data Dictionary.

• (l) is the internal length specification.

• t is the data type.

• d is the number of decimal places (used only with type p).

• 'xxx' is a literal or previously defined variable that supplies a default value.

Examples of parameters defined with the parameters statement.

parameters p1(2) type c.
 parameters p2 like p1.
 parameters max_value type i default 100.
 parameters cur_date type d default '19980211'.