These procedures are similar to the Xlib procedures
XInternAtom and XGetAtomName. Tk_InternAtom
returns the atom identifier associated with string given by
name; the atom identifier is only valid for the display
associated with tkwin. Tk_GetAtomName returns the
string associated with atom on tkwin's display. The
string returned by Tk_GetAtomName is in Tk's storage: the
caller need not free this space when finished with the string, and
the caller should not modify the contents of the returned string.
If there is no atom atom on tkwin's display, then
Tk_GetAtomName returns the string “?bad atom?”.
Tk caches the information returned by Tk_InternAtom and
Tk_GetAtomName so that future calls for the same information
can be serviced from the cache without contacting the server. Thus
Tk_InternAtom and Tk_GetAtomName are generally much
faster than their Xlib counterparts, and they should be used in
place of the Xlib procedures.