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2014-05-14 13:11

Ghostrider
Administrator

Posts: 45

Understanding kernal names CHKIN and CHKOUT

The kernal input/output routines have names given by Commodore in the C64 Programmer's Reference Guide (among other places). Some of these names can seem a bit cryptic at first, like the name SETLFS which apparently means "SET Logical, First, and Secondary addresses", even though at first just mentioned as "Set up a logical file".

Now, for the names CHKIN and CHKOUT, which define a channel as input or output, the CH part probably stands for CHannel, and the IN/OUT parts for INput and OUTput. But what about the K???

To me, "checkin" or "checkout" does not seem likely, as I cannot find the word "check" used in this connection by Commodore. It cannot stand for Keyboard, as the functions deal with other devices as well. Standing for Kernal perhaps... no, this explanation does not seem entirely satisfying in this connection. Why mention the kernal in this kernal function and not in the others.

Sometimes the clues to Commodore's naming of these labels are hidden away in a sentence somewhere, even in other manuals and books.

Has anybody encountered a hint about the missing K somewhere?
Or has a guess?

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2014-05-16 06:47

Oswald

Registered: Apr 2002
Posts: 5094

soci has leading

2014-05-16 07:56

Ghostrider
Administrator

Posts: 45

I agree, soci's answer seems most plausible to me. It is supported by the fact that: of all the names mentioned under "user callable kernal routines" in the C64 Prog.Ref.Guide, the only name where it is obvious that "channel" is part of the name, is in CLRCHN, where they chose to represent "channels" by CHN. As Urban Space Cowboy hints at, they probably wanted to eliminate the two functions being mistaken for "character in" and "character out" (CHRIN/CHROUT), and therefore "CHIN" and "CHOUT" would have been bad choices of naming, so they needed another letter instead of the R of CHRIN/CHROUT. Had they wanted the word "channel" in the two names then they would have probably become "CHNIN" and "CHNOUT", consistent with CLRCHN. So, to me, CHange Kernal INput/OUTput seems most likely - and actually makes sense :)

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