Difference between a structure and a field symbol?
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Structures are used to define the data at the interface of module pools and screens and to define the parameter types of function modules.
The central definition of structures that are used more than once makes it possible for them to be changed centrally. The active ABAP Dictionary then makes this change wherever required. ABAP programs or screen templates that use a structure are automatically adjusted when the structure is changed.
There are Flat, nested and deep structures. A flag structure only references elementary types. A nested structure references at least one further structure, but not a table type. A deep structure references at least one table type.
Field symbols: are placeholders or symbolic names for other fields. They do not physically reserve space for a field, but point to its contents. A field symbol cam point to any data object. The data object to which a field symbol points is assigned to it after it has been declared in the program.
Whenever you address a field symbol in a program, you are addressing the field that is assigned to the field symbol. After successful assignment, there is no difference in ABAP whether you reference the field symbol or the field itself. You must assign a field to each field symbol before you can address the latter in programs.
Structures are used to define the data at the interface of module pools and screens and to define the parameter types of function modules.
The central definition of structures that are used more than once makes it possible for them to be changed centrally. The active ABAP Dictionary then makes this change wherever required. ABAP programs or screen templates that use a structure are automatically adjusted when the structure is changed.
There are Flat, nested and deep structures. A flag structure only references elementary types. A nested structure references at least one further structure, but not a table type. A deep structure references at least one table type.
Field symbols: are placeholders or symbolic names for other fields. They do not physically reserve space for a field, but point to its contents. A field symbol cam point to any data object. The data object to which a field symbol points is assigned to it after it has been declared in the program.
Whenever you address a field symbol in a program, you are addressing the field that is assigned to the field symbol. After successful assignment, there is no difference in ABAP whether you reference the field symbol or the field itself. You must assign a field to each field symbol before you can address the latter in programs.
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