BASIC's question mark and PRINT
frustum at pacbell.net
Mon Nov 21 14:26:52 CST 2005
>>Subject: Re: BASIC's question mark and PRINT
>> From: Jim Battle <frustum at pacbell.net>
>> Date: Mon, 21 Nov 2005 13:03:31 -0600
>> To: General Discussion: On-Topic and Off-Topic Posts <cctalk at classiccmp.org>
>>tim lindner wrote:
>>>In BASIC, where did the short cut of '?' for PRINT originate?
>>>After following a discussion on the CoCo list I thought I'd ask here.
>>Here are some bounds and data points.
>>The Dartmouth BASIC specification does not have ? as an abbrevation (circa 1964).
>>I think all versions of Microsoft BASIC have this shortcut (circa 1975).
>>Palo Alto Tiny BASIC (li chen wang) didn't use this convention -- instead it
>>Wang BASIC (circa 1972) didn't use this convention.
>>From what I can tell, DEC BASIC didn't use this abbreviation.
> The ? was adopted by convention from the fact that early MS basic
> (MITS BASIC) the ? was also the same value as the token for print.
> Most of the non-compiled 8bit basics were tokenized in memory for
> execution and storage and when "LIST"ed were detokenized to list as
> Basic we know.
Allison, that seems unlikely. Later versions of microsoft basic certainly
didn't use any value lower than 0x80 for tokens. Even if you could find a few
characters in the "live" portion of the ascii table that didn't lead to
ambiguous parsing, I can't think of a good reason why they'd do it -- there was
enough room at 0x80 and above, and not enough unused values below 0x80, so why
have two lookup tables when one would do?
It would seem much easier to have special case where '?' got mapped to the token
OK, trying to be less speculative, I looked at the binary for
ALTAIR BASIC VERSION 3.2 [EIGHT-K VERSION]
that is included with Rich Cini's Altair emulator. At the end is the list of
the statement keywords. In memory each keyword abuts the next, and the boundary
between keywords is marked by setting the msb of the byte. Here is the table in
Since there no room for storing a token value after each item (I know it is
possible that that mapping is held elsewhere, but it seems unlikely), these
keywords very likely have consecutive token values.
Elsewhere in the binary, near the beginning, is a similar table for the
functions (FN, SPC, NOT, AND, OR, VAL, CHR, LEFT, RIGHT, MID, FRE, SIN, COS,
TAN, PEEK, etc, but also including THEN, STEP).
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