Allison wrote:
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 used "P.".
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
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 for PRINT.
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 order:
END
FOR
NEXT
DATA
INPUT
DIM
READ
LET
GOTO
RUN
IF
RESTORE
GOSUB
RETURN
REM
STOP
OUT
ON
NULL
WAIT
DEF
POKE
PRINT
CONT
LIST
CLEAR
CLOAD
CSAVE
NEW
TAB(
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).