Some of the fields and numbers can be modified using one or more names as the following
|Type||Typical Length||Typical Range|
|X||1 byte||Any byte values (00 to FF)|
|C||1 char||1 to 65535|
|N||1 char||1 to 65535|
|D (date)||8 chars||8 characters|
|T (time)||6 chars||6 characters|
|I||4 bytes||-2147483648 to 2147483647|
|F||8 bytes||2.2250738585072014E-308 to 1.7976931348623157E+308 positive or negative|
|P||8 bytes||[-10^(2len -1) +1] to [+10^(2len -1) 1] (where len = fixed length)|
|STRING||Variable||Any alphanumeric characters|
|XSTRING||Variable||Any byte values (00 to FF)|
WRITE / ...可用于换行，相当于
The complex types are classified into Structure types and Table types. In the structure types, elementary types and structures (i.e. structure embedded in a structure) are grouped together. You may consider only the grouping of elementary types. But you must be aware of the availability of nesting of structures.
When the elementary types are grouped together, the data item can be accessed as a grouped data item or the individual elementary type data items (structure fields) can be accessed. The table types are better known as arrays in other programming languages. Arrays can be simple or structure arrays. In ABAP, arrays are called internal tables and they can be declared and operated upon in many ways when compared to other programming languages. The following table shows the parameters according to which internal tables are characterized.
|Line or row type||Row of an internal table can be of elementary, complex or reference type.|
|Key||Specifies a field or a group of fields as a key of an internal table that identifies the table rows. A key contains the fields of elementary types.|
|Access method||Describes how ABAP programs access individual table entries.|
Reference types are used to refer to instances of classes, interfaces, and run-time data items. The ABAP OOP run-time type services (RTTS) enables declaration of data items at run-time.