GB836198A - Improvements in or relating to data processing systems - Google Patents

Abstract

836,198. Magnetic data-storage apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. July 19, 1956 [July 19, 1955; Dec. 21, 1955], No. 22363/56. Class 106 (1). The equipment described can transfer a block of ten eleven-decimal-digit words from a three-dimensional magnetic core matrix, 87, Fig. 2b, to a magnetic tape 83, Fig. 2a, or vice versa, and its design is determined primarily by the codes used to represent data on the tape and in the core matrix. In the core matrix each decimal digit is stored in a seven-bit biquinary code (i.e. having bits weighted 0, 5, 0, 1, 2, 3, and 4) and a word is either numeric, when each decimal digit represents a digit (the same digit), or alphanumeric, when each pair of decimal digits represents either a letter or a digit, whereas on the tape only one code, a 1, 2, 4, 8, A, B, C code is used for both and digits and letter digits being represented by a combination of 1, 2, 4 and 8 bits and letters by a combination of these bits together with A and B bits, the C bit being a redundant parity check bit. The correspondence between the two-digit core code and the tape code is shown in Fig. 10, the two digits of the core code being labelled even and odd. When the block of data being transferred contains numeric words only, the digits of the words are re-coded and transferred one-by-one in turn. Such a transfer is called a numeric transfer. When a transfer, for example from the core matrix to the tape, involves a block of data including one or more alphanumeric words, Fig. 8, the first word of the block, word WO, is used as a control word to indicate whether each of the following words is alphanumeric or numeric and to control their re-coding. Of the control word, digits D10-D2 thereof are associated with words W9-W1 respectively, the presence of an eight in the control word indicating that the associated word is an alphanumeric word and the presence of any digit other than eight in the control word indicating that the associated word is a numeric word. For example the eight in the D3 position of word W0 indicates that word W4 is an alpha-numeric word, the digits 8 and 3 in the D10 and D9 positions thereof representing a T and the digits 9 and 4 in positions D8 and D7 representing a 4, and the word is recorded on the tape as shown in Fig. 9, whereas the nine in position D7 of the control word indicates that word W6 is a numeric word. For such a transfer first the control word is transferred to the tape digit-bydigit, being re-coded as a numeric word, and then the digits of the control word, starting with that in position D2 are each read from the matrix again immediately before their associated words are transferred to control their re-coding. In a similar transfer from the tape to the core matrix the control word is first entered into the matrix and then its digits are red in turn, from the matrix, to control the transference of the following words from the tape. The digit in the DO position of a word represents, in the case of a numeric word, its sign and is associated on the tape with the digit in position D1 (see for example words W5 and W6) and in the case of alphanumeric this digit, though usually a nine, has no significance. An actual transfer takes place in the following manner : first one of four latches, 131-134, Fig. 2a, specifying whether the transfer is from the matrix (read) or to the matrix (write) and whether it is alphanumeric or numeric, is set " on." This causes the tape to start moving and, after a suitable delay, a series of control pulses is produced by a chain of single-shot multivibrators 153, 122-126, Fig. 2b. These pulses are initiated for a read transfer, at suitable intervals either by a clock 150 or by the bits read from the tape, for a write operation. For a read numeric transfer these pulses cause one digit (seven-bits) to be read first from the matrix into seven buffer latches 88, and then back into the matrix from the buffer latches, then the digit is passed via a gate 97 and a code translator 95 to seven write triggers which control the write heads. For an alphanumeric transfer a digit in an evennumbered position is read first and registered in seven storage latches 111 and then the next digit of the word is read, resulting in two digits being applied to the code translator simultaneously. Specification 800,273 is referred to.