ABAP (Advanced Business Application Programming)

             
           ABAP is a programming language that runs in the SAP ABAP Runtime environment, created and used by SAP for the development of application programs including Reports ,Module Pool Programming, Interfaces, Forms , Data conversions ,User Exits & BADI.
          All of R/3’s applications and even parts of its basis system were developed in ABAP. ABAP is an event-driven programming language. User actions and system events control the execution of an application. ABAP is also called ABAP/4. The “4” in ABAP/4 stands for “Fourth Generation Language” or 4GL.

ABAP WORKBENCH 
The ABAP Workbench is used by SAP for the development of standard and custom application software. The ABAP Workbench is also used to create dictionary objects. 
It consists of the following components −
1.  ABAP Editor is used to maintain programs.
2.  ABAP Dictionary is used to maintain Dictionary objects.
3.  Repository Browser is used to display a hierarchical structure of the 
     components in a package.
4.  Menu Painter is used to develop graphical user interfaces including menu
     bars and toolbar's.
5.  Screen Painter is used to maintain screen components for online programs.
6.  Repository Information System contains information about development and
     run time objects, such as data models, dictionary types and table structures,
     programs,and functions.
7.  Test and Analysis Tools, such as the Syntax Check and the Debugger.
8.  Function Builder, which allows to create and maintain function groups and   
     function modules.
9.  Data Modeler, a tool which supports graphical modeling.
10.Workbench Organizer, which maintains multiple development projects
     and manages their distribution.





Operators in SAP ABAP
In the abap we have 3 types of operators 
1.Mathematical Operator
2.Comparative Operator
3.Relational (or) Logical Operator

1. Mathematical Operator:
 • Basic operations : +,-, / and * along with functions like sin, sqrt etc. are 
    Supported
 • Priority of the operations :  functions , exponential , multiplication 
   division ,addition , substraction.



2. Comparative Operator :-

 

3. Relational (or) Logical Operator :-



Comments in SAP ABAP :-
1.Comments are the non-executable statements these are used to improve
   the readability of the program
2.If we want to comment the entire line then we place * at the first character of 
   the line
    *----------------------------------------
3.If we want to comment the line we use “
   Ex: c = a + b  “Adding a and b

Data Types and Data Objects in ABAP :-
Data Types in abap:-
1.Data types are pure descriptions.
2.There is no memory associated with data types.
3.Data types describe the technical properties of data objects

ABAP Data types can be divided into elementary, reference, and complex types.
1 . Elementary  Types: – They  are  data  types  of  fixed  or  variable length 
    that  are  not made up of other  data  types. In  variable data  types  the 
    memory  space  used  by  the  data objects  changes dynamically  during 
    runtime  and  their  definitions  can  be  altered  later.  This  is not so with 
    fixed length data types.
                      In  predefined  data  types,  you  are allowed  to  define 
    elementary  data  types  on  your  own  in  ABAP  by  making  use  of the 
    TYPES statement.  You  base  these  on  the  predefined  data  types.  You 
    can  define your own technical attributes.

2. Reference  Types: – These  data  types  describe  reference  variables,  which 
    are  data  objects  that have  references  in  them.  Reference  variables  are 
    components  of  a  complex  data  object like structures or internal tables.

3. Complex  Data  Types: – Complex  data  types  are  those  that  are  made 
    up  of  other data types. They are of two types – structured types and table
    types.Structures  are  used  to  group  together  work  areas  that  logically 
    belong together. The  various  elements  of  a  structure  may  be  of  any 
    type, or can be a different structure or internal  Structures  may  be 
    classified as Nested  and  non- nested  structures or Flat and deep structures.
    Nested structures contain one or more other structures as components,    
    unlike non-nested structures. Flat structures contain only elementary data    
    types of fixed length. Deep  structures contain  at least one internal table, 
    reference type, or a string as a component.
                    Internal  tables  may  contain  a  series  of  lines  that  are  all  of 
    the same data type.  Internal  tables  have  a  line  type,  which  is  used  to 
    identify table rows using a unique or non- unique  key  and  a table type that 
    determines just how individual table entries, whether non- sorted, sorted 
    index tables or hash tables are accessed.

Data objects :-
1.Data objects are the physical units a program uses at runtime.
2.Each data object has a specific data type assigned to it.
3.Each data object occupies some space in memory.
The various data objects in ABAP are:
1 .Literals: – Literals   exist  in  the  program  source  code  and have a fixed 
    technical attribute such as field length, number of decimal places and data 
    type. But literals are nameless.
2. Named  Data  Objects: – They  are  data  objects  that  have  a  name  using
    which you may address the ABAP program. They include text symbols, 
    constants and variables.Text symbols are nothing but pointers to texts 
    present in the text pool.Variables are  data  objects  which  have  contents 
    that  may  be  changed  in an ABAP program using program  statements. To
    declare  variables, you should use statements such as DATA, CLASS-DATA, 
    STATICS, PARAMETERS, SELECT -OPTIONS, and RANGES. Constants are data
    objects whose contents cannot be changed.
3. System-Defined Data Objects: –System- defined data objects are available 
    at run- time always and don’t have to be declared explicitly .
4. Interface  Work  Areas:  – Interface  work  areas  work  as  interfaces 
    between programs, screens,and logical databases and are declared with 
    statements such as TABLES and NODES.
5. Objects:  – They  are  anonymous  data  objects  that  are  nameless  and 
    declared  using CREATE OBJECT command.

Control Statements  :-
This are used to control the flow of execution of the program Controlling the  Flow of ABAP/4 Programming:
The flow of an ABAP/4 program can be controlled internally  and externally.
Internal control is steered  by using some standard  control keywords( IF,CASE, DO,WHILE).
Control structures are 2 types :-
1.Branching Control structures(IF,CASE)
2.Looping Control structures(DO,WHILE).
External control is steered by events . Events are generated either from other ABAP/4 programs (system programs or user programs) or from interactive user input (like, for example, using the mouse to click on the screen).
Programming Logical Expressions
Use logical expressions in conditions statements with key words
 IF, CHECK and WHILE to compare data fields.
         comparisons with all field types
         comparisons  with character strings and numeric strings
Comparisons with all field types:
Use following operators in logical expressions for comparisons
with all field types
          EQ(=)
          NE(<> or ><)
          LT(<)
          LE(<=>)
          GT(>)
          GE(>=)

TYPE and LIKE in ABAP :- 
TYPE : It will allocate memory during execution (object type) 
          TYPE will improve performance.
          It is used when user defined object link with SAP system data type.
          TYPE refers to the user defined data types
          TYPE,assign datatype directly to the data object while declaring.
      
LIKE : Tt will allocate memory immediatly.
          It is when data object link with the other data object.
          LIKE refers to existing data type of data object
          LIKE,you assign the datatype of another object to the declaring data     
          Object. The datatype is referenced indirectly.

Text Elements  :- 
Text elements are used to store texts displayed on the selection screens or output screens of ABAP reports, but are not hard-coded in programs. The different types of text element include:
Report or program titles
List headers
Column headers
Selection texts
Text symbols
Field String  :-
A field string is a type of variable, and is the equivalent of a structure in the DDIC but is defined within an ABAP/4 program. Like a structure, a field string is a series of fields grouped together under a common name. The difference lies mainly in where the definition resides. The term structure in R/3 applies only to a Data Dictionary object containing a collection of fields. The term field string applies to a collection of fields defined in an ABAP/4 program.
Two statements are usually used to define field strings in an ABAP/4 program:
Data
Tables
Syntax for Defining a Field String Using the DATA Statement
The following is the syntax for defining a field string using the data statement.
data: Begin of fs1,
        f1[(l)] [type t] [decimals d] [value 'xxx'],
        f2[(l)] [type t] [decimals d] [value 'xxx'],
        ...
       End of fs1.
Output Statement in ABAP
Basic form
WRITE f.
Additions
1. … AT pl (position and length specification,before the field)
2. … option (formatting option)
3. … ofmt (output format by field)
4. … AS CHECKBOX (output as checkbox)
5. … AS SYMBOL (output as symbol)
6. … AS ICON (output as icon)
7. … AS LINE (output as line)
Effect
Outputs the field f in the correct format for its type to the current list. The field f can be:
a field declared by DATA ,
a component of a structure declared by TABLES ,
a field symbol (FIELD-SYMBOLS ),
a text literal which is not language-specific
a language-specific text literal (text symbol).


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