Hi Abdul,
first of all I suggest you to look into the detailed info material available here in this space. A good introduction for developers is to look into our reference scenario page: ABAP for SAP HANA Reference Scenario
With our SAP HANA Database existing ABAP Coding will still run like on any other database. But with SAP HANA you also have the possibility to leverage specific features of this database.Information about these features can be found here: New ABAP for HANA features in SAP NW 7.4 SP5
If you want to try it out yourself, here is a new end-to.end guide: Brand-new ABAP 7.4 for SAP HANA End to End Deve... | SCN
Hope this helps, Cheers
Jens