Complete beginners to SAP ABAP programming may refer to my Blog for basics and how to get started stuff. Others having experience or basic knowledge of SAP ABAP may proceed to explore the below topics:
Object oriented features were gradually introduced to ABAP starting from Release 4.0 and the language slowly transitioned from ABAP/4 to ABAP Objects. This section includes some resources on object-oriented features of modern ABAP called ABAP Objects.
Commonly used Function modules
Function modules are part of SAP modularzation techniques. There are thousands of Function modules and it's not possible for a single person like me to provide a comprehesive list. I am restricting myself to keep it minimum at this juncture but will try to add more as time permits.
Lists a few helpful transaction codes. Since the list of transaction codes provided by SAP is exhaustive, it is not possible to discuss all of them and that is not the objective of this space as well.
Check many of the online resources for WD4A on different features.
Tried to provide some ABAP code for you to check the language capability and features.
A few helpful standard SAP programs.
Useful Resources
Components of SAP Communication technology
Internet Communication Framework (ICF)