Well, in one way, this is an easy question to answer: function code 9 in
QDOS (output string) uses a terminating dollar sign because CP/M BDOS
function code 9 does [1], and QDOS was just a CP/M clone. So I guess Gary
really meant that no one knows why BDOS function code 9 requires a
terminating dollar sign.
I had always just assumed it was another DEC-ism in CP/M, of which there are
many. Drives and devices with names of the form "foo:", PIP (peripheral
interchange program), the use of forward slashes for program options, etc.
At any rate, I'd guess it's probably the same reason why $ means end-of-line
in Unix regular expressions.
- Joe
Joseph S. Barrera III <joebar@acm.org>
<http://research.microsoft.com/~joebar/>
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