There are storages which are still more expensive than the ring cores; they are our old friends, the flip-flops. These are bound to be much dearer, for they need not only one threaded ring for storing each bit, but a complete electronic switch made up of at least two transistors. On the other hand, flip-flops have the advantage - and they are without rivals - in that they demand practically no access time at all. They can be switched by pulses from "0" to "1" (and back again) - that is their storing procedure. They will release the pulses they have in store and send them on their way when instructed to do so. There is no loss of magnetism, no remagnetization necessary, no reading wires. An inquiry pulse is simply sent through the flip-flop. If it is at "0" the inquiry pulse sticks. If the flip-flop shows a "1," the pulse runs through and passes on, and the access time is just as long as a transistor needs to make a switchover.
Because of this extraordinarily short access time, flip-flops we frequently used in the accumulator (the most important part of the computer's memory) when calculations are to be done with co-ordinating matrices. If expense is no object, they can also be used as ordinary intermediate storages or as working storages, when they carry addresses just like the core storages.
Addresses are indispensable in every storage. The magnetic drum, for example, can be divided up on its outer surface into small sectors, and each one of them means an address. In punched tapes, the addresses are inserted in addition to the numbers and data, and they are magnetized on to magnetic tapes. If such a tape is to serve merely as an auxiliary storage, of course, it is not customary to provide each number with an address of its own.
Usually whole groups of numbers - figures to be added up, collections of technical data or the statement of an account - are combined in a single address. A combination of this kind is called a "block." As the arithmetic unit is unwilling to cooperate with the slow magnetic tape, all the data noted on the tape must be "re-stored" on ring cores before calculations can start. The machine always collects for that purpose the whole block of numbers from the magnetic tape and moves the figures, one after the other, into the addresses of the core storage. The current balance of Mr. Jones's bank account, which had been noted on the tape as the fifth item in the block of numbers, is now in core storage address No. 1005. Mr. Morgan, who would formerly have been able to find his account as the thirty-seventh number in the collective address, will now be able to locate it at the specific address No. 1037.
The machine counts with these individual addresses. If it has done its job properly and altered the accounts, all numbers from the individual addresses will be copied - one after the other - under a joint address, in block forms on the magnetic tape. And them they stay until the first of the next month.
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