SAP ABAP - A Brief Introduction to Reports and Module Pool Programming

Posted by : Unknown Saturday, June 1, 2013

Getting Started: SAP-ABAP

Just a few steps ahead before we get our hands dirty. It’s necessary to know the concept and other technical related things in ABAP.

ABAP stands for Advanced Business Application Programming.

It’s a programming language similar to COBAL and the programs we do will not be stored as a separate external file like JAVA/C++ programs. All ABAP programs reside inside the SAP database.

As in other programming languages, an ABAP program is either an executable unit or a library, which provides reusable code to other programs and is not independently executable.

ABAP distinguishes two types of executable programs:

· Reports ( Can be executed directly )

· Module pools ( They can be executed only via a ‘TRANSACTION CODE’ )

REPORTS:

Reports follow a relatively simple programming model whereby a user optionally enters a set of parameters and the program then uses the input parameters to produce a report in the form of an interactive list. Reports are used to display data from the SAP database. Mostly they use the SAP standard screen ‘1000’.

Example:

You have created a report program which gives the employee id of all the employees in your company filtered by some parameter (take department code as parameter).so when you execute the program it will ask for department code and gives the result.

Here is the example of the output, how it would look like.

MODULE POOL:

Module pools are used to get data from the user and store in the SAP database as well as to display them from the database. They contain user defined screens designed using screen painter. (Remember whenever we create screens in module pool program we have to name them in numbers, and so we should not name our screens as ‘1000’ because its SAP’s standard screen is ‘1000’, which it uses in report programming and selection screens. Each screen has its own flow logic, which is divided into a "PBO" (Process before Output) and "PAI" (Process after Input) section. The term “dynpro” (dynamic program) refers to the combination of the screen and its flow logic.

After all your programming you can’t directly execute a module pool program, you have to create a ‘TRANSACTION CODE’.

What is a transaction code?

Transaction code is a short cut key attached to a screen. It should have only numbers and characters (ztcode or zt42).for example if you create a transaction code for your program, and enter the transaction code the program will be executed and the corresponding screen will be called.

To make it clear and easier lets have an example,

Example:

<don’t worry about the programming logic, just try to understand this example, we shall see the programming logic later>

You have created a program that first requires a validation (i.e. you have to enter your user_name and password) and then you will be redirected to your screen where you will have all the details of you salary, expense and all.

(to make get the point)

So, here we have to create two screens,

Assume Screen no. 2000 for validating the user_name and password.

Screen no. 2001 for details of salary, expense.

Now create a transaction code, eg; zuser01

Now, when you enter the transaction code this the magic that happens, J

So, from this you will have clear that PBO Executes before the screen and PAI loads after receiving an input from the user.

So we will have a command like this in PAI.

**********************************************

PAI of screen 2000.

When ‘SUBMIT’ <when submit button is clicked>

Call screen 2001. <the next screen is called>

**********************************************

The next PBO of screen 2001 loads and the screen will be displayed

OK, now come back to the point so far we have seen executable programs in SAP ABAP. Now we shall have a little explanation for non-executable programs.

Include modules: An INCLUDE module gets included at generation time into the calling unit; it is often used to subdivide very large programs.

Example:

INCLUDE zemployee.

Subroutine pools: Subroutine pools contain blocks of code enclosed by FORM /ENDFORM statements and invoked with PERFORM.

Example:

PERFORM zemployee.

When the compiler comes into the above line, the commands or programs inside the subroutine zemployee will be executed <i.e. the commands within FORM and ENDFORM of the subroutine name, here ‘zemployee’>

FORM zemployee

ENDFORM

Function groups: Function groups are libraries of self-contained function modules enclosed by FUNCTION / END FUNCTION and invoked with CALL FUNCTION.

Object classes and Interfaces: Object classes and interfaces are similar to Java classes and interfaces; the first define a set of methods and attributes, the second contain "empty" method definitions, for which any class implementing the interface must provide explicit code.

Type pools: Type pools define collections of data types and constants.