slot.i1.v = myslot_letter()

	This routine returns the application program 'slot letter', e.g., if
	the program is running in the PA_SLOT or SA_SLOT the value 'A' will be
	returned.  If the program is not running in a P*_SLOT or S*_SLOT
	a value of '?' will be returned
	This function returns status values as follows:

	'?' on error

	This function requires the following include files:

	cnsparam_h, clib_h

	Related functions:

	myconsole, myinstance, mynode, myname, my_ascii_name, my_gen_name,
	my_generic_ascii_name, mypage, clib_environment, my_executable_name_c,
	my_user_name, my_acnet_user_name, myslot, myslot_index,

	C/C++ usage:

	char slot_letter;

	slot_letter = myslot_letter();