On Fri, 19 Jan 2007 14:58:24 -0500, "John W. Kennedy"
<jwkenne@[EMAIL PROTECTED]
> wrote:
>hancock4@[EMAIL PROTECTED]
wrote:
>> OFF TOPIC:
>>
>> On the IBM 1401, I heard that one has to issue two "clear storage"
>> instructions to totally clear out storage. The first execution clears
>> out a ****tion, the second clears out the rest. Something to do with
>> the print area, which is a reserved section of storage?
>>
>> Any explanation would be appreciated.
>
>Monstrously twisted, though one can just barely make out the original
>truth through the fog. The CS instruction cleared downward from the
>given address through (inclusively) the next lower xxx00 address. So it
>would take as many as 160 CS instructions to clear all of storage,
>starting at 15999 (or whatever the high address was) and going down by
>100s to 99.
All the way to 0. :-) A "/099" would clear from 99 to 0.
>
>The read, punch, and print areas were all reserved, in 1-80, 101-180,
>and 201-332. In addition, 0 and 100 were volatile (they were used by the
>card reader and card punch), and 87-89, 92-94, and 97-99 were the
>(optional) index registers.
The CS command would still clear the reserved areas.
I knew that location 0 was used by the reader, but hadn't known about
100.
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