Which paper tape hole is bit 1?

vrs vrs at msn.com
Sat Nov 19 11:06:33 CST 2005


From: "Allison":
> Nominal PDP-8 use was short BIN loader hand toggled in. Load bin 
> tape that contains small BIN format program or loads the RIM
> loader for more complex programs (basic, focal).  BASIC would
> then read an ascii program tape.

It's a nit, but you have the roles of BIN and RIM reversed in 
this paragraph.  You also omitted a discussion of the checksum, 
field setting, and comment features allowed in a BIN tape :-).

For those who care, BIN tapes have an extra 'data' pair at the 
end which forms a checksum.  Bytes with both of the most significant 
bits set use the next three bits to select which bank or 'field' 
is loaded.  And arbitrary 'comments' may appear between rub-outs 
(which have all bits set).  RIM tapes have none of these features.
Both BIN and RIM tapes use leader-trailer with just the MSB set.

There are at least two versions of the BIN loader.  I don't know 
offhand if the older BIN loader supported all the features or 
not.

    Vince



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