What makes a screen editable, read only or to create?

[Chris]

What makes create,edit and view screen to function in different ways. How does JSD knows this screen can only read or it can be edited. 

[Nic Brough -Adaptavist- · Accepted solution]

Code.

The screens and fields are coded differently.  In fact, there are only two functional types of screen in Jira - view and edit.  The create screen is simply an edit-type screen that is displayed at create time.

Code does all the rendering, and where the screen is in use is what determines how it grabs fields.  Fields also are coded with a view mode and an edit mode, done with "templates", and a create/edit screen renders the edit mode version of a field, and a view screen calls the view "template" for the field.