Every tag type has its own default initial value:
- Boolean: false.
- Numeric: 0.
- Variable length string: an empty string
- Fixed length string: a string of requested length filled with spaces (or other pad character defined by the tag class.
- Object: null (an object tag cannot have custom initial value).
A custom initial value of a tag can by provided by the tag class the tag belongs to or by using the initialValue tag property.
