ANSI INCITS ISO 962-1974 Information Processing - Implementation of the 7-Bit Coded Character Set and its 7-Bit and 8-Bit Extensions on 9-Track 12 7 mm (0.5 in) Magnetic Tape《信息处理..pdf

1、INTERNATIONAL STANDARD 962 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION .MEELIYHAPOJIH.UI OPI-AHWMLWI IlO CTAHAAFlIl3AUW.DRGANISATION INTERNATIONALE DE NDRMALISATION Information processing - Implementation of the 7-bit coded character set and its 7-bit and 8-bit extensions on g-track 12,7 mm (0.5

2、in) magnetic tape Traitement de linformation - Mathrialisation du jeu de caractkes codt% ii 7 Mments et de ses extensions B 7 et 8 ISO/R 1863, g-track 32 tpmm (800 rpi) magnetic tape for information interchange; IS0 ., g-track 63 rpmm (1 600 rpi) phase-encoded magnetic tape for information interchan

3、ge. 1) 2.3 The magnetic labelling is the subject of ISO/R 1001, Magnetic tape labelling and file structure for information interchange. 3 DEFINITIONS (The figure on page 3 illustrates the following definitions.) 3.1 magnetic tape : A tape which will accept and retain magnetic signals intended for in

4、put, output and storage purposes on computers and associated equipment.*) 3.2 track : A longitudinal area on the tape along which a series of magnetic signals may be recorded?) 3.3 reference edge : The edge farthest from an observer, or nearest the top of a page, when a tape is lying flat with the o

5、xide side uppermost and the direction of movement for recording from left to right.*) (See figure.) 3.4 row : A transverse area on the tape along which magnetic signals of tracks are recorded. 3.5 block : A series of rows, limited by suitable marks, to be recorded and read as a group. 3.6 gap : A sp

6、ace left unused between blocks. 3.7 8 position environment : A set of eight positions, each available to record one bit. 4 SPECIFICATIONS 4.1 Track identification There shall be 9 tracks on the tape and they shall be numbered consecutively from 1 to 9, with track 1 adjacent to the reference edge (se

7、e figure). 4.2 Data content Each row contains one character only, with its parity check bit. 1) At present at the stage of draft proposal. 2) Definitions in accordance with ISO/R 1864, Unrecorded magnetic rape for information interchange - 8 and 32 rpmm 1200 and 800 rpil. NRZI, and 63 rpmm I1 600 rp

8、il, phase-encoded. 1 Copyright American National Standards Institute Provided by IHS under license with ANSINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-ISO962-1974 (E) 4.3 Constitution of data blocks ) All blocks for data interchange shall consist of not less t

9、han 18 data rows and not more than 2 048 data rows and, in addition, those checking characters and block framing characters as required by the relevant International Standard for recorded magnetic tape. 4.4 Error protection1 ) 4.4.1 Parity of data rows The parity track shall be track 4 and the bit r

10、ecorded on that track will be chosen so that the number of ONE bits recorded on the same row is odd. 4.4.2 Longitudinal check row This row is written at the end of a block and itscontent is such that the number of ONE bits recorded on the same track is even for the whole block with this longitudinal

11、 check row. 4.4.3 Cyclic redundancy checking ) 4.5 Control blocks (Tape Mark) ) For the purpose of separating data, a control block, known as the Tape Mark, shall be allowed. The exact use of the Tape Mark is described in ISO/R 1001. The Tape Mark configuration is defined in the relevant IS0 publica

12、tionsl). For certain recording modes, this block shall be accompanied by a longitudinal check row. 4.6 Representation of coded characters 4.6.1 Sequence of coded characters Considering the recorded data as being in character form, the sequence of characters from the start towards the finish of a blo

13、ck shall correspond to the normal left-to-right sequence of a written line. 4.6.2 Arrangement of 7-bit coded characters The relationship of the 7 bits to the 8 positions of the environment is as follows : Bits of the 7-bit combination : q b7 be b5 b, b, b, bl Position number of the environment : 8 7

14、 6 5 4 3 2 1 q is a high order bit with value ZERO 4.6.3 Arrangement of g-bit coded characters The relationship of the 8 bits to the 8 positions of the environment is as follows : Bits of the 8-bit combination : aa a7 a6 a5 a4 a3 a2 al Position number of the environment : 8 7 6 5 4 3 2 1 4.6.4 Envir

15、onment relationship to tracks The relationship of the 8 positions of the environment and of the parity bit to the 9 tracks of the tape is as follows : Parity (P) and position number of the environment : P 8 7 6 5 4 3 2 1 Track number : 4 7 6 5 3 9 1 8 2 1) Block framing, error protection techniques

16、and constitution of control blocks vary according to the recording mode and the packing density. See the documents referred to in 2.2. 2 Copyright American National Standards Institute Provided by IHS under license with ANSINot for ResaleNo reproduction or networking permitted without license from I

17、HS-,-,-IS0 962-1974 (E) - Longitudinal check row location Block W- Reference edge +I: 6 Forward tape motion - Resultant recording direction - NOTES 1 Tape is shown with oxide side towards observer. 2 Tape is shown representing bit ONE in all tracks. L Track numbers FIGURE -g-track magnetic tape Copyright American National Standards Institute Provided by IHS under license with ANSINot for ResaleNo reproduction or networking permitted without license from IHS-,-,-