摘要: Character or byte-oriented data link control protocols have had a profound influence on the rapid and successful development of communications networks. Although subject to certain limitations which led now emerging bit-oriented protocols, character-oriented served our industry very well. Because widespread implementation, they can be expected continue this service into foreseeable future. This paper offers an overview characteroriented their place in hierarchy. It examines these from historical evolutionary perspective. provides details, with examples, structure, functions, characteristics, operation family protocols.