Arabic diacritics

hi,

regarding the Arabic diacritics. e.g. for the Shadda, we
have:

1. The form that people type:
http://unicode-table.com/en/0651/

2. An Isolated form. It should be the same, but looks different in the
Unicode table, which is confusing me now.
http://unicode-table.com/en/FE7C/

3. A medial form:
http://unicode-table.com/en/FE7D/

When do I use 1/2, and when do I use 3?

some diacritics has e.g. isolated and medial forms. Some have
only one of these forms, some have both. So, where does each of them go?

respectfully
Received on Fri May 15 2015 - 09:51:14 CDT