1、INTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION MEXflYHAPOflHAR OPTAHA3AUMR IlO CTAHnAPTH3AUHW.ORGANISATION INTERNATIONALE DE NORMALISATION Information processing - Implementation of the 7-bit coded character set and its 7-bit and 8-bit extensions on 3,81 mm magnetic tape casse
2、tte for data interchange Traitement de Iinformation - Matkrialisation du jeu de caracttkes B 7 Bl coded character set : A set of unambiguous rules that establishes a character set and the one-to-one relationship between the characters of the set and their bit combinations. 3.5 code extension: Techni
3、ques for the encoding of characters that are not included in the character set of a given code. 3.6 environment: The characteristic that identifies the number of bits used to represent a character in a data processing or data communication system or in part of such a system. 4 RECORDING FORMAT Accor
4、ding to IS0 3407, the data to be interchanged are recorded serially by bit and by character. Each character is located in a byte of eight bit-positions along the track. The bit-positions in a byte are numbered from 1 to 8 in order of recording. The following diagram summarizes these concepts : byte
5、Bit-positions : . . . 32187654321876. Forward tape motion : -w Resulting recording direction : - 5 RECORDING OF 7-BIT CODED DATA Each 7-bit coded character is recorded in bit-positions 1 to 7 of a byte; bit-position 8 is recorded with value ZERO. The relationship is as follows : Bits of the 7-bit co
6、mbination : q 0 b7 bs b5 b4 b, b, bl Bit-position in the byte : 8 7 6 5 4 3 2 1 6 RECORDING OF 8-BIT CODED DATA Each g-bit coded character is recorded in bit-positions 1 to 8 of a byte. The relationship is as follows : Bits of the g-bit combination : a8 a7 a6 a5 a4 a3 a2 al Bit-position in the byte : 8 7 6 5 4 3 2 1 1) At present at the stage of draft. 1
