SAP ABAP [2020] - Module Pool Program - Chain EndChain 

SAP ABAP - Module Pool Program in ABAP
What is SAP ABAP?
ABAP is a high-level programming language created by the German software company SAP SE.
ABAP is one of the many application-specific 4th generation languages first developed in the 1980s.
It was originally the report language for SAP R/2, a platform that enabled large corporations to build mainframe business applications for materials management and financial and management accounting.
In ABAP we have basically 2 types of programs:
1)Reports
2)Module pools
The module pool program defines more complex patterns of user interaction using a collection of screens.
The term “screen” refers to the actual, physical image that the user sees.
Each screen also has a "flow logic", which refers to the ABAP code implicitly invoked by the screens, which is divided into a "PBO" (Process Before Output) and "PAI" (Process After Input) section.
Dynpro - Dynamic program - refers to the combination of the screen and its flow logic.
Introduction to ABAP module pool programming.
Module pool programs are also called dialog programs.
The module Pool programs are basically reports that are prepared for different screens and to manage the sequence of events of these screens.
In the transaction SE80, you can see all the dynpros that you have for this kind of report, add new ones, add all types of element to the report.
In this program, we will see how to provide field validation using CHAIN ENDCHAIN in module pool program.