Modularization in ABAP

Modularization in ABAP

When you modularize source code, you place a sequence of ABAP statements in a module. Then, instead of placing all of the statements in your main program, you just call the module.When the program is generated, the source code in the modularization unit is treated as though it were actually physically present in the main program.

SAP- ABAP Macro

Include Programs

Subroutines

Function Modules

Function Groups


SAP- ABAP Macro
If you want to reuse the same set of statements more than once in a program, you can include them in a macro.
You can only use a macro within the program in which it is defined, and it can only be called in lines of the program following its definition.

Macros  can be useful for long calculations or complex WRITE statements.

Syntax

DEFINE <macro_name>

'Macro Statements

END-OF-DEFINITION
Macros can use Parameters &N where N = 1,2,3...
Example:-

DATA: number1 TYPE I VALUE 1.

DEFINE increment.

ADD 1 to &1.

WRITE &1.

END-OF-DEFINITION.

Increment number1.

WRITE number1.
Output: 2
Include Programs
Include Programs are solely for modularizing source code, and have no parameter interface. Include programs allow you to use the same source code in different programs. They  can be useful if you have lengthy data declarations that you want to use in different programs.
Syntax

Include <include program Name>
Points to Note
Include programs cannot call themselves.
Include programs must contain complete statements.
Example:
INCLUDE ZILX0004.

WRITE: / 'User', SY-UNAME,/ 'Date', SY-DATUM.

================================

PROGRAM ZRPM0003.

INCLUDE ZILX0005.
Subroutines
Subroutines are procedures that you can define in any ABAP program and also call from any program. Subroutines are normally called internally, that is, they contain sections of code or algorithms that are used frequently locally. If you want a function to be reusable throughout the system, use a function module.
Syntax-

FORM <Subroutine> [<pass>].

<Statement block>.

ENDFORM.
<Subroutine> = Name of the subroutine


<pass> = Parameters being passed

Types of Subroutines

Internal
Subroutine defined in same program being called.
Can access all the data objects declared in the main ABAP/4 program.
External
Subroutine defined outside the program being called.
Need to use the <pass> option or declare data objects in common parts of memory.
Calling a Subroutine Internal Subroutines
PERFORM <subroutine> [<pass>]
<subroutine> = Name of the subroutine
<pass> = Parameters being passed

Data declared in main program is automatically available.

External Subroutines

PERFORM <subroutine>(<Program>) [<pass>].

PERFORM <subroutine> (<Program>) [<pass>] [IF FOUND].

PERFORM (<subroutine>) IN PROGRAM  (<Program>) [<pass>] [IF FOUND].

PERFORM <index> OF <subroutine1> <subroutine2> <subroutine3> [<pass>].
Points to Note
Nested calls are allowed in subroutines (i.e. PERFORM within a FORM ... ENDFORM ).
Recursive calls are also possible.
To define local data, use the DATA statement after FORM . Each time you enter the subroutine, the data is recreated (with an initial value) and released at the end (from the stack).
To define global data used within a subroutine, use the LOCAL statement after FORM . The values are saved when you enter the subroutine and then released at the end (from the stack)
Function Modules
Function Modules are general purpose ABAP/4 routines that anyone can use. Infact , there are a large number of standard function Modules available.
Function Modules are organized into Function Groups: Collections of logically related functions. A Function module always belongs to a Function Group.

Syntax-

FUNCTION <function module>

<Statements>

ENDFUNCTION.

Important information Associated with Function Module
Administration
Import/Changing/Export parameters.
Table Parameters/Exceptions.
Documentation
Source code - L<fgrp>U01 . <fgrp> is the Function Group
Global Data - L<fgrp>TOP .Global data for the function group- Accessible across function modules in the function group.
Main Program - SAPL<fgrp> . Contains the list of all the include files for that function group
Call a Function Module
To call a function module, use the CALL FUNCTION statement:

CALL FUNCTION <module>

[EXPORTING  f1 = a 1.... f n = a n]

[IMPORTING  f1 = a 1.... f n = a n]

[CHANGING   f1 = a 1.... f n = a n]

[TABLES     f1 = a 1.... f n = a n]

[EXCEPTIONS e1 = r 1.... e n = r n [ERROR_MESSAGE = r E]

[OTHERS = ro]].
Function Groups
Function groups are containers for function modules. Infact, there are a large number of standard Function Groups. All of the function modules in a function group can access the global data of the group.
Like executable programs (type 1) and module pools (type M), function groups can contain screens, selection screens, and lists.


Function Groups cannot be executed.
The name of a function group can be up to 26 characters long.
When you create a function group or function module, the main program and include programs are generated automatically.
Function groups encapsulate data.

ABAP Syntax
ABAP Statements
ABAP Program Types

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