Basic things in ABAP with example

Arithmetic expressions in ABAP

In ABAP you can program the following valid arithmetic expressions,

Parameters

In our previous program we have written a set of commands for the arithmetic operations but the input to the variables where hardcoded in the program itself, now what if the user wants to enter the value during runtime?

What if he wants to enter different values each time?

So, we have to write a program which asks input from the user and gives the output.

To get input from user we should use the abap keyword ‘PARAMETERS’.

Ex:

PARAMETERS: input1 type I,

            input2 type I.

 The variable Result should not be defined in parameters because we are not going to get an input to the variable result. (Therefore result should be defined by ‘DATA’)

Data types in abap

Data types

A data type or simply type is a classification for identifying types of data, such as integer, numeric, character etc. that determines the possible values for that type; the operations that can be done on values of that type; the meaning of the data; and the way values of that type can be stored.

Here in abap we can classify them into two groups.

Complete types:

Type for date (D), format YYYYMMDD, LENGTH 8

Type for time (T), format HHMMSS, LENGTH 6

Type for integer (I), LENGTH 4

Type for floating point number (F), LENGTH 8

Type for dynamic length character string

Type for dynamic length byte sequence (HeXadecimal string)

Incomplete types:

Conditional branches and logical expressions

In ABAP you have two ways to execute different sequences of statements.

 As we know about the IF-statement and CASE-statement lets update our previous program (arithmetic calculation) using these conditional statements.

As you can see the keyword ‘PARAMETERS’ is used for getting input from user, we are getting three inputs from the user.

And the output is stored in the variable ‘RESULT’ which is defined by the ‘DATA’ keyword.

Next comes the conditional operator,

IF-statement:

 It checks whether the value in variable ‘SYMBOL’ is one of the symbols described there.

If the symbol is any of these ‘+, - , *, /’ it comes to the next statement (i.e. CASE-statement) or else it executes the ‘ELSE’ part.

CASE-statement:

Depending upon the symbol the case statement is executed i.e. when the symbol is ‘+’ it executes the addition and when the symbol contains the value ‘-‘ the operation subtraction is performed.

Whenever an operation is performed the result is stored in the variable ‘RESULT’, and at the end of the CASE-statement we are printing the result in the screen.

Now, come back to the IF-statement (line 16).

If the symbol contains value which is not defined there, it comes to the ELSE part.

The ELSE part contains the code for writing an error ‘symbol is not defined in the program’.

In line 16 the Relational operator OR is described after every condition.

See how the compiler reads the program.

Line16 -> Checks whether the value in symbol is ‘+’ OR‘-‘ OR‘*’  OR ‘/’ .

(If the value in symbol is any of the following above Line18 is executed or else Line 30 is executed)

Getting Hands Dirty : ABAP-EDITOR

I would like to remind a few things, 

SAP is a Three (3) tier architecture. 

And in SAP-ABAP, SQL commands can be used; we can have NATIVE SQL or OPEN SQL. But will go with OPEN SQL.

------------------------------------------------------------------------------------------------------------

The one you are seeing above is the screen when you log-in to SAP from your desktop or PC  

<the screen above is the presentation layer>

On top of the window are the menus, below the menu there is a text box with a green tick, here is where we should enter the ‘TRANSACTION CODE’.

Here are some are some commonly used transaction code.

So, first let’s have a sample report program.

Go to Transaction -> SE80 -> REPOSITRY BROWSER -> <in the drop down choose> PROGRAM -> <below the drop down enter the program name> ZSAMPLE and press ENTER.

screen 1.1

A popup will appear as above conforming to create a program, click YES.

Un Check the TOP INCL <if you check it will include a ‘TOP INCLUDE in your program>

and 'enter'.

Choose Status as ‘TEST PROGRAM’ and click SAVE.

                                                   screen 1.3

It will ask for package, for now save it as local object.

Finally your program editor will be opened.

Now, we are going to write a program to do all the arithmetic operations.

And now the arithmetic operations take place, the result is stored in the variable result.To display the result,we should use a keyword “WRITE” similar to cout and printf in c and c++..CLEAR keyword clears the memory of the variable next to it, so after that the variable will not be holding any values.

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’ )

  

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,

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.

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

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. 

<for the last three, giving examples will make you confuse, when we get our hands dirty we shall have a clear look on those types>