scope:

Specifies the structure of 8-bit codes and 7-bit codes which provide for the coding of character sets. The code elements used in the structure are common to both the 8-bit and 7-bit codes. The codes use a variety of techniques for extending the capabilities of elementary 8-bit and 7-bit codes. Greater emphasis is given to 8-bit codes in this edition of the standard than in previous editions because they are now more widely used. The use of commonn elements in the 8-bit and the 7-bit code structure enables any specific conforming 8-bit code to be transformed into an equivalent 7-bit code, and vice versa, in a simple and direct fashion. ISO/IEC 4873 conforms to the 8-bit code specified here, and ISO/IEC 646 conforms to the 7-bit code strcture specified here. The code structure facilities specified here include various means of extending the number of control functions and graphic characters available in a code. They also include techniques to construct and formalize the definition of specific codes, and to provide a coded identification of the structure and of the constituent elements of such specific codes.