XmInternAtom — A macro that returns an atom for a given name "XmInternAtom" "atoms"

XmInternAtom returns an atom for a given name.  The returned atom remains defined even after the client's
       connection closes. The returned atom becomes undefined when the last connection to the X server closes.

       display   Specifies the connection to the X server

       name      Specifies  the  name  associated  with  the  atom you want returned.  The value of name is case
                 dependent.

       only_if_exists
                 Specifies a Boolean value.  If False, the atom is created even if it does not  exist.   (If  it
                 does  not  exist,  the  returned  atom  will be None.)  If True, the atom is created only if it
                 exists.

XmInternAtom — A macro that returns an atom for a given name "XmInternAtom" "atoms"

       Returns an atom.

                                                                                                 XmInternAtom(3)

       #include <Xm/AtomMgr.h>
       AtomXmInternAtom(
       Display*display,
       Stringname,
       Booleanonly_if_exists);