Re: SV: Re: Shifting memory to the right

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#81

From: glen herrmannsfeldt
Date: Mon, 10 Oct 2005 15:29

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Someone wrote:

> Old channel connected tape stations could read tapes backwards
> and moved byte after byte to memory. The result was a block
> with bytes in reversed order. You used MVCIN to restore the block.

Read Backwards puts the bytes in memory starting from the end of
the buffer, so they end up in the original order, though for short
blocks they will be at the end of the buffer instead of the beginning.

Someone else wrote:

> MVCIN (a) is no longer supported and (b) moved data in reverse order, so
> C'ABCDE' would be moved as C'EDCBA'.  Very useful if you put a card in the
> reader backwards, I'm sure, but I for one could never think of a real use
> for it.

Rumor is that it was an RPQ for a company in Israel to correct for
languages written right to left on the page.  Sometime later it
was added as an instruction set optional feature, supported on many
later S/370's.  I am not sure which machines after that did or did
not support it.

-- glen

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From: glen herrmannsfeldt <gah@ugcs.caltech.edu>
Newsgroups: bit.listserv.asm370
Subject: Re: SV: Re: Shifting memory to the right
Date: Mon, 10 Oct 2005 08:29:41 -0700
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