Data dictionary

Data dictionary is a central source of data in a data management system. Its main function is to support the .It has details about
- What data is contained ? - What are the attributes of the data ? - What is the relationship existing between the various data elements ?

functions of the debugger screen

- Single step(F5) - Use this option to step through the program statement by statement. This allows you to branch into subroutines and function modules, and to execute these routines step by step as well.
- Execute(F6)- Use this option to process a program line by line. All of the statements on the current line are processed in a single step. If you are positioned on a line that calls a subroutine and you choose Execute, the Debugger processes the whole subroutine and then moves on to the line following the subroutine call. This allows you to jump through the statements within the subroutine.
- Return(F7) - The Debugger returns from a routine to the point at which control returns to the main program.
- Continue(F8)- Use this option to process the program up to the next dynamic or static breakpoint or up to the cursor position.

Different types of views

1. Database views 
2.  Projection views
3.  Help views
4.  Maintenance views
5.  Structure views
6.  Entity views 

Basic objects of ABAP/4 Dictionary

• Tables
• Data Elements
• Structures
• Domains

Size Category

It describes the probable space requirement of the table in the database.
There are five size categories (0-4) and 11 data classes, only three of which are appropriate for application tables:
- APPL0 - Master data (data frequently accessed but rarely updated)
- APPL1 - Transaction data (data that is changed frequently)
- APPL2 - Organizational data (customizing data that is entered when system is
configured and then rarely changed)

Type of a table or structure

There are the following table types:

• transparent table
• structure
• append structure

Internal Table and Types ABAP

STANDARD table Key access to a standard table uses a linear search. This means that the time required for a search is in linear relation to the number of table entries. You should use index operations to access standard tables.
SORTED table Defines the table as one that is always saved correctly sorted. Key access to a sorted table uses a binary key. If the key is not unique, the system takes the entry with the lowest index. The runtime required for key access is logarithmically related to the number of table entries.
HASHED table Defines the table as one that is managed with an internal hash procedure You can only access a hashed table using the generic key operations or other generic operations ( SORT, LOOP, and so on). Explicit or implicit index operations (such as LOOP ... FROM oe INSERT itab within a LOOP) are not allowed.
INDEX table A table that can be accessed using an index. Index table is only used to specify the type of generic parameters in a FORM or FUNCTION. That means that you can't create a table of type INDEX. Standard tables and sorted tables are index tables.
Syntax : DATA itab TYPE table type of line type [WITH UNIQUE/NON-UNIQUE KEY ] [Iini size n] [WITH HEADER LINE]