PDP-11 tape question

[Chuck Guzis]

On 6/23/20 8:18 PM, John Forecast wrote:

> Looks like a standard DOS/BATCH-11 tape file header. The first 6 bytes and the last 2 bytes are the file name in rad50 - “HMMMD0P.SAV”.
> Depending on where/when it was written the header can be either 12 or 14 bytes:
> 
> Format of DOS-11 magnetic tape header records:
> 
> 	.rad50	/fn1fn2/	;1st 6 letters of filename
> 	.rad50	/ext/		;3-letter extension
> 	.byte	proj,prog	;ppn (display it in octal)
> 	.word	prot		;protection code, usually <233> octal
> 	.word	date		;date: (year-1970.)*1000.+(day within year)
> 	.rad50	/fn3/		;[optional] letters 7::9 of filename
> 
> Length=14. bytes (or 12. if no fn3, like in actual DOS/BATCH)

Thanks for straightening that out--all I know is that the tapes are from
an 11/70, which isn't much information, admittedly.

--Chuck