From: arne@vajhoej.dk

On 1/31/2025 6:42 PM, Craig A. Berry wrote:
> On 1/31/25 4:05 PM, Dan Cross wrote:
>> Treating -1 as true in BASIC seems rather common, from the quick
>> survey I did; I speculate that this is almost certainly due to
>> the bit representation of -1 having all bits set, while in BASIC
>> the integer type is (usually?) signed, thus -1 on a two's
>> complement machine.  I wonder what the original DTSS BASIC did?
>
> I had a quick look at:
>
> https://ia601901.us.archive.org/34/items/bitsavers_dartmouthB_3679804/
> BASIC_4th_Edition_Jan68_text.pdf
>
> and didn't see an obvious answer, though I didn't read the whole thing
> and could've missed something.  The exact values of true and false might
> well have been considered an implementation detail that should not be
> relied on.

Or maybe true and false did not exist.

I noted that the manual defined IF THEN as:

IF [formula] [relation] [formula] THEN [line number]

and not:

IF [formula] THEN [line number]

Arne

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