ARTICLE
Data Types
Data types are a subtree of the ABAP type
hierarchy . Data types are only type descriptions. Data types do not
have any attached memory for storing working data, but they may require
space for administration information. A data type characterizes the
technical properties of all data objects
that have this type. In ABAP, data objects occur as attributes of data
objects, but they can also be defined as stand-alone data types.
The definition of stand-alone data
types is based on a set of
predefined data types . Stand-alone data types can either be defined
internally in the program using the statement TYPES
in the global declaration section of a program, in the
declaration section of a class, locally in procedures, or for all
programs in the ABAP Dictionary . Data
types in ABAP Dictionary are either created directly as
repository objects or in a
type group .
Predefined and self-defined data types can be used to generate data
objects and for typing . For the latter in
particular, predefined generic data
types are available. A generic data
type is a data type that does not determine all the properties of a
data object . Generic data types can only
be used for typing formal parameters
and field symbols .
Data types can be divided into elementary, reference, and complex types.
Elementary types are 'atomic' in
the sense that they are not composed of other types. They are further
classified into elementary types of fixed length and of variable length.
There are 13 predefined elementary data
types of fixed length in ABAP. There are four
character-like types: text fields
( c ), numeric text fields ( n ), date fields ( d ), and
time fields ( t ). There are seven
Acht
numeric types: Integers ( b ,
s , i
int8
), decimal floating point numbers ( decfloat16 , decfloat34
), binary floating point numbers ( f ), and packed numbers ( p
). Byte-like type: Byte fields
( x ). The data types c , n , x , and p
are generic in terms of length. p is also generic in terms of the
number of decimal places. The numerical data types b and s
cannot be specified directly in programs for short integers.
There are two predefined elementary
data types of variable length in ABAP. There is one
character-like type: Text string (
string ). Byte-like type:
Byte string ( xstring ).
Reference types describe data objects
that contain references to other objects (data objects and instances of
classes), which are known as
reference variables . There are no predefined reference types in ABAP.
A reference type must either be defined in the ABAP program or in ABAP
Dictionary. Reference types form a hierarchy, which represents the
hierarchy of the objects to which the references can point.
Complex data types are composed of
other types. They enable the administration and processing of
semantically related datasets under one name. A data object of a complex
type can be accessed overall or by component. With the exception of the
structure sy , there are no predefined
complex data types in ABAP. A complex type must either be defined in the
ABAP program or in ABAP Dictionary. There are two types of complex data
type:
A structured type is a sequence of
any elementary reference or complex data types. Structures are used for
grouping together work areas that logically belong together.
Table types consist of a sequence of any
number of rows of the same data type. Table types are characterized by a
row type , which can be any elementary data
type, a reference data type, or a complex data type. They are also
characterized by the table type , which
defines how tables can be accessed, and by a
table key , which is used to identify the table rows.
Documentation extract taken from SAP system, � Copyright SAP AG. All rights reserved