hi check this..
in this choose data types..
User-defined Data Types
User-defined data types can either be elementary or structured. User-defined elementary data types are based entirely on predefined elementary data types. To define your own elementary data types, you use the TYPES statement.
User-defined elementary data types make your programs easier to read and maintain by giving them descriptive names that are easier to understand and more recognizable.
The TYPE statement never allocates data space in memory, whereas the DATA statement always does.
Elementary data types cannot be included in further components. Structured data types, on the other hand, are made up freely of elementary and structured data types.
In structured data types there is a difference between field string types and table types:
Field string types (known as structures or records in other terminology) can be made up of components of any type.
Table types (known as arrays in other terminology) can be made up of lines of any type.
Field string types and table types at the highest level can themselves contain further field string types and table types.
user defined data types is nothing but whatever u hav defined in ur table tat start with z and ur data type may be refers to a Elementary Types,Complex Types,Structures....
Elementary types are the smallest indivisible unit of types. They can be grouped as those with fixed length and those with variable length.
Fixed-Length Elementary Types
There are eight predefined types in ABAP with fixed length:
Four character types:
Character (C), Numeric character (N), Date (D), and Time (T).
One hexadecimal type:
Byte field (X).
Three numeric types:
Integer (I), Floating-point number (F) and Packed number (P).
Variable-Length Elementary Types
There are two predefined types in ABAP with variable length:
STRING for character strings
XSTRING for byte strings
Reference types describe data objects that contain references (pointers) to other objects (data objects and objects in ABAP Objects). There is a hierarchy of reference types that describes the hierarchy of objects to which the references can point. There are no predefined references - you must define them yourself in a program.
Complex types are made up of other types. They allow you to manage and process semantically-related data under a single name. You can access a complex data object either as a whole or by individual component. There are no predefined complex data types in ABAP. You must define them either in your ABAP programs or in the ABAP Dictionary. Structured types are divided further into structures and internal tables.
A structure is a sequence of any elementary types, reference types, or complex data types.
You use structures in ABAP programs to group work areas that logically belong together. Since the elements of a structure can have any data type, structures can have a large range of uses. For example, you can use a structure with elementary data types to display lines from a database table within a program. You can also use structures containing aggregated elements to include all of the attributes of a screen or control in a single data object.
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Edited by: Alvaro Tejada Galindo on Jun 9, 2008 4:06 PM