Patent GB-885163-A (GB)
Title: Improvements in and relating to programming systems
IPC: G06F9/04
Filed: 1958-10-24
Abstract: 885,163. Performing iterative digital data processing routines. INTERNATIONAL BUSINESS MACHINES CORPORATION. Oct. 24, 1958 [Oct. 25, 1957], No. 34132/58. Class 106 (1). A programme is recorded on a master record medium, e.g. magnetic tape or disc, or paper tape, and selected sections are recorded on a subsidiary record medium. Preferably the sections are instructions defining an iterative procedure which is controlled from the subsidiary medium and a section is repeatedly duplicated on the subsidiary medium until the iterative procedure is concluded by a balance test. As described the record medium is paper tape, instructions being fed to a utilization device 87 from either a master tape 17 or a subsidiary tape 31 as required. Associated with tape 17 are reader and punch 1, with tape 31, reader and punch 2. Each instruction word is coded in six channels on the tape, five containing the operation and the sixth determining whether the instruction is of class 0 or 1. The control system includes a class response unit 77 which determines in response to instruction whether instructions of both classes or of only one class are obeyed. Normal operations are of class 0. A programme A, I 1 , B ... , of which I 1  is an iterative procedure, is punched on tape 17 by keyboard 50. It is assumed that the system initially is responsive only to class 0 instructions. The following steps are then performed: (a) Section A of the programme is executed. Signals are sent from reader 1 to class response unit 77 and thence to utilization device 67. Included in Section A is the instruction " DUP 2 " which causes a circuit to be closed through unit 67 by which anything read by reader 2 is duplicated on tape 31 by punch 2. The last instruction of Section A is " DUP 1-2 " by which a similar circuit is closed through unit 55 causing words read by reader 1 to be punched on tape 31 by punch 2. (b) Section I 1  of the programme on tape 17 is executed and simultaneously punched on tape 31 as (I 1 )1 by punch 2 in response to the instruction " DUP 1-2 ". The first instruction of I 1  is " Reader 1 " but this is of class 1 and is not obeyed. The last instruction of I 1  is " Balance test; DUP 1-2 OFF." This opens the circuit between reader 1 and punch 2 and causes a comparison in the utilization device of some variable used in the iteration procedure against a constant. It is assumed that the test is negative and thus no signal issues from device 87 to class response unit 77. The instruction following section I 1  is " Reader 2 " which activates reader 2 while inactivating reader 1. Tape 17 stops. (c) Reader 2 causes (I 1 )1 to be executed while punch 2 duplicates (I 1 )1 as (I 1 )2 on tape 31. At the conclusion of the second iteration (I 1 )1 the balance test is again performed and it is assumed that the result is again negative. (d) Reader 2 causes (I 1 )2 to be executed while punch 2 duplicates (I 1 )2 as (I 1 )3 on tape 31. It is now assumed that the result of the balance test is affirmative, on which result a signal issues from comparing device 85 to class response unit 77 that class 1 instructions are to be obeyed. Reader 2 continues to section (I 1 )3 and meets the class 1 instruction Reader 1 which inactivates reader 2 and activates reader 1. Iteration of I 1  is now concluded. (e) The next section of tape 17 is a " clean up " section preparing the system for section B of the programme. The first instruction is of class 1 reading " Class 0 OFF " which renders the system insensitive to class 0 instructions. Then follow class 1 instructions " DUP 2 OFF " opening the circuit between reader and punch 2, and " Reader 2 " switching to reader 2. Since normal instructions are of class 0 reader 2 reads the remainder of (I 1 )3 without causing them to be obeyed, until reaching the class 1 instruction " Reader 1 " duplicated from the beginning of (I 1 )3 by punch 2. This switches control to reader 1 and use of the subsidiary tape is concluded. The final instructions are Class 1, " class 0 ON," and class 0 " class 1 OFF." A DUP 1 control 53 is provided so that e.g. section A of the programme may be duplicated on to the master tape by punch 1 as it is read. A relay system for controlling the above sequence is described in detail. Specification 600,896 and U.S.A. Specifications 2,376,371, 2,619,532 and 2,636,672 are referred to.