SAP ABAP Internal Tables Questions

SAP ABAP Internal Tables Questions

1. what is an internal table?
   
2. how many type of internal tables are there?
   
3. what is the difference between hashed & sorted internal tables?
   
4. what is the difference between standard and sorted internal tables? (in performance wise)
   
5. Difference between internal table and a dictionary table?
   
6. can you create an internal table dynamically?(at run time)
   
7. what is the use of select for all entries in an internal table?
   
8. when you are using 2 internal table in program, you have decided to use for all entries
   statement to retrieve data but unfortunately there are no records in the first internal table. What will be the result? (2nd internal table contains records).
9. in a loop of an internal table, what is the use of at first & at last statements?
   
10. What is the use of at new statement?
    
11. what is the difference between at first & at new statements?
    
12. what is a binary search ? and how it is useful in a sorted internal table?
    
13. when do you need to create an internal table with header line ?and with out a header line?
    
14. what does it mean occurs 0 while creating an internal table?
    
15. what will happen if you don't give occurs clause while creating an internal table?
    
16. what is the difference between clear, delete & refresh with respect to an internal table?