ABAP Keyword Documentation →  ABAP − Release-Specific Changes →  Changes in Releases 4.0 and 4.5 

Extended Concept for Field Symbols in Release 4.0:

The extended field symbol concept can be summarized as follows:

• The behavior of typed and untyped field symbols has been standardized.
  

• New logical expression <fs> IS ASSIGNED
  

• New statement UNASSIGN <fs>

Other versions: 7.31 | 7.40 | 7.54

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The new logical expression <fs> IS ASSIGNED allows you to query whether a field has already been assigned to the field symbol <fs>.

The new statement UNASSIGN <fs> sets the field symbol <fs> so that it is not pointing to a field.

The expression IS ASSIGNED, and the ASSIGN and UNASSIGN statements allow you to find out and change the state of a field symbol at any time. This means that you can simplify your ABAP programs, and make them less error-prone.

Further changes

• Dynamic ASSIGN (ASSIGN (f) TO <fs>.):
  If <fs> is an untyped field symbol and the contents of f are invalid, ,the field symbol is not set.
  

• ASSIGN with offset and length for VALUE parameters in FORMS and FUNCTIONS:
  A runtime error is triggered if you use ASSIGN f+off(len) TO <fs> to address beyond the area of the VALUE parameter f.
  

• Non-assigned field symbols with INSERT, SORT and AT:
  If the field symbol <fs> has not yet been assigned (using ASSIGN), it is ignored in the following statements:
  ,, INSERT <fs> INTO fg.
  ,, SORT BY <fs>.
  ,, SORT itab BY <fs>.
  ,, AT NEW <fs>.
  ,, AT END OF <fs>.