Atom Creation and Usage Count

An application creates a local atom by calling the AddAtom function; it creates a global atom by calling the GlobalAddAtom function. Both functions require a pointer to a string. The system searches the appropriate atom table for the string and returns the corresponding atom to the application. In the case of a string atom, if the string already resides in the atom table, the system increments the reference count for the string during this process.

Repeated calls to add the same atom name return the same atom. If the atom name does not exist in the table when AddAtom is called, the atom name is added to the table and a new atom is returned. If it is a string atom, its reference count is also set to one.

An application should call the DeleteAtom function when it no longer needs to use a local atom; it should call the GlobalDeleteAtom function when it no longer needs a global atom. In the case of a string atom, either of these functions reduces the reference count of the corresponding atom by one. When the reference count reaches zero, the system deletes the atom name from the table.

The atom name of a string atom remains in the global atom table as long as its reference count is greater than zero, even after the application that placed it in the table terminates. A local atom table is destroyed when the associated application terminates, regardless of the reference counts of the atoms in the table.