the computer before processing. Before accepting an input, the computer will check that the transaction line number is next in sequence to that recorded in the computer record and that the new computed balances after posting the transactions agree with the balances reported. There will thus be a check that balances on the unit record and balances on the computer record are in agreement at the end of every transaction. Mr. R. E. Cox (Ministry of Aviation): For obvious reasons, you have designed your system on the basis of using a five-unit code (ignoring the special use of the seven-unit system on radio circuits for error correction purposes). Have you felt cramped by this; have you felt that it would have been advantageous to you in any way if you could have used a code with a greater number of information bits per character? Wing Cdr. Davey: We have not felt unduly cramped by using the five-unit code. Only numeric data is transmitted from units and depots. We would have preferred to use our computer code rather than the Telex code, but the cost of modifying the standard G.P.O. equipment we are using was prohibitive. Mr. J. T. Whittaker (H.M. Treasury): It is understood that very large amounts of paper tape will be read in by way of 1,000 characters a second punched paper tape readers. The condition of the paper tape is therefore of prime importance. Paper is prone to stretch or shrinkage under certain atmospheric conditions. Tolerances might be exceeded. Were any steps being taken to ensure that the reperforators were in an air-conditioned area of the building? Wing Cdr. Davey: This problem has been recognized. To overcome it, arrangements were made for conditioned air to be circulated through each reperforator cabinet by way of trunking from the main air-conditioning plant. Mr. R. K. Chisham (I.B.M., U.K. Ltd.): Has the speaker considered on-line connection of (at least) highpriority demands direct to the computer, thus eliminating the reperforators, obtaining faster response, and saving the manpower required for manipulation and transfer of paper tape? Wing Cdr. Davey: On-line connection to the computer was considered but rejected for the following reasons.