Introduction to SAP ABAP for beginners

ABAP is defined as Advanced Business Application Programming; it is a 4th generation language from SAP. SAP ABAP is used for developing applications for SAP R/3 system. SAP will run the applications which are written using ABAP/4. ABAP/4 cannot run on any operating system as it requires a set of programs to load, interpret and buffer its input and also output.
Architecture of R/3 is a three tier:
1. Database Server
2. Application Server
3. Presentation Server
There are many types of ABAP/4 programs follows as:
    Executable Programs
    INCLUDE program
    Module Pool
    Sub-Routine Pool
    Interface Pool
    Class Pool
    Type Pool
    Function Group

Executable Programs (ABAP Reports): Executable Programs are I programs type that represented with the keyword REPORT
INCLUDE Program: INCLUDE Programs are the programs type that represented with the keyword INCLUDE
Module Pool/Dialogue programs:  These are type M programs represented with the keyword PROGRAM.
Sub-Routine Pool: Sub-Routine Pool is S programs type that represented with the keyword PROGRAM
Interface Pool: Interface Pool is J programs type that represented with the keyword INTERFACE-POOL
Class Pool: Class Pool is K programs type that represented with the keyword CLASS-POOL.
Function Group:  Function Group is F programs type that represented with the keyword FUNCTION-POOL
Type Pool: Type group are represented with the keyword TYPE-POOL