[Simh] SIMH tape images to real tapes

[Johnny Billquist]

On 2014-05-18 05:10, Rich Alderson wrote:
>> Date: Sat, 17 May 2014 18:26:33 +0200
>> From: Johnny Billquist <bqt at softjar.se>
>
>> On 2014-05-15 23:10, Clem Cole wrote:
>
>>> In 9-track world, the end of each file is mark as a single meta record
>>> (tape mark),  Two in the row marks end-of-tape.   So the when you write
>>> a take the driver check to see if its at start of tape and if not, has
>>> to backs up over the last tape mark and then start writing.  On close it
>>> writes 2 tape marks.
>
>> The two tape marks for logical EOT is a convention, and not all software
>> adhere to it. But in general, right. I think someone else mentioned it,
>> but it's worth pointing out that for ANSI labelled tapes, the tape marks
>> are not used this way, for example.
>
> Actually, tape marks are used in just this way on ANSI and IBM/EBCDIC tapes.
> The "headers" and "trailers" of labeled tapes are physically separate files,
> with the physical demarcation of tape marks and interfile gaps and all that
> telling the OS where to find them.

Right. And logical EOT is marked by a block saying so, and not by two 
consecutive tape marks... :-)

You might hit two consecutive tape marks in the middle of an ANSI 
labelled tape. (Not common, but definitely possible.)

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
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