Difference between Subroutine and Functionmodule

[Former Member]

Dears,

Here i post one question, even though it is simple for you people, plz answer for me.

Thanks in advance,

Rajesh.N

[Former Member]

Here is the notes of differences bet. FM and Subroutines.

Hi Function modules are for modularization urpose. You can the Function Module in any program. That is available all over in the SAP system.

Where as subroutine is program specific. Once you create a subroutine in one program then you can use that in that program and related programs like includes in the program or you have to call the subroutine specifically using the main program name.

Finally subroutines are for program modularization. Not for generic use.

FM's are for generic use. Not program dependent.

FMs are mainly used when a routine is to be performed by many programs.

Subroutines (forms) are generally only executed within one program.

You can perform routines from other programs, but it's not often done.

both forms and FMs are reusable modularization units.

To distinguish we generally say that forms are used for internal modularization and

FMs are used for external modularization.

To decide on which to implement, consider whether you need the content to be used just for a limited program

or wheteher it can be called from many independent programs.

For the first purpose it is better to implement a form whereas for the second we implement an FM.

However, ABAP does not isolate the usage context.

That is; you can call a form from another program within whose code the form is not actually implemented.

However, this requires attention since the form may utilize global variables.

The same issue holds for FMs.

FMs are encapsulated in function groups and function groups may have global variables that can be globally

used by all FMs inside it.

Award Points...

[Former Member]

Hi,

In contrast to normal subroutines function modules have uniquely defined interface. Declaring data as common parts is not possible for function modules. Function modules are stored in a central library.

[Former Member]

Refer this link...

http://www.sapbrainsonline.com/FAQs/TECHNICAL/SAP_ABAP_MODULARIZATION_FAQ.html

http://abapcode.blogspot.com/2007/05/modularization-techniques.html

U will find all the differences in above links...