[TUHS] origin of null-terminated strings

[Clem Cole]

More info WRT to historical DEC usage ...
---------- Forwarded message ---------
From: Bob Supnik
Date: Fri, Dec 16, 2022 at 4:39 PM
Subject: Re: Origin of ASCIZ / null terminated char arrays.
To: Clem Cole


It wasn't in the PDP8. The PDP8 mostly used sixbit, the ASCII subset
between 40 and 137. The character was simply masked by 077, so that 100
(@) became 0 and could be used as the delimiter. PAL8 (in OS8) does not
have a text generation pseudo-op.

The PDP7 had a TEXT pseudo-op that <did> fill an extra word with 0s if
the string was a multiple of 3 characters. It supported FIODEC, BAUDOT,
and ANALEX encodings, but not ASCII.

The PDP9 has both .SXBIT and .ASCII. The latter used two 18-bit words to
hold five 7bit ASCII characters. In both cases, words were zero-filled,
but an extra (word) of 0s was not added if the string was a multiple of
2/multiple of 5 characters.

The PDP11 had .ASCIZ, starting with Macro11 in 1972.

Tim can comment on the PDP10.

> ᐧ
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