Re: NUL to terminate strings; was reinventing ASCII?

In article
<da33b5f9-4d2f-4c30-9f20-d72722c0d67e@[EMAIL PROTECTED]
>,
	James Harris <james.harris.1@[EMAIL PROTECTED]
> writes:
> On 6 Mar, 10:34, torb...@[EMAIL PROTECTED]
 (Torben Ægidius Mogensen)
> wrote:
>> James Harris <james.harri...@[EMAIL PROTECTED]
> writes:
> ...
>> Why would we need a null character?  I know that it in C is used as
>> end-of-string marker, but that is a horrible design decision.  If any
>> single character should mark the end of a string, it should be EOT.
> My vague inference (which I've never had tested) is that the null
> string terminator is a consequence of C's pointer model. 

Null terminated strings pre-date C.  Macro-11 had them and with Unix and
the first C compiler being developed on a PDP-11 that may be where C got
the idea.

>                                                           C is designed
> to allow a pointer to any memory object to be taken. This means C can
> depend only on knowing
> 1. the address
> 2. the type
> of any given object when it is operating on that object. The address
> is passed between modules. The type is derived lexically. This has
> consequences:
> 1. strings need a terminating character
> 2. arrays have no knowledge of bounds when operated upon
> 3. header files are needed to share other info between compilation
> units
> 4. a number of functions require a count/length to be passed
> The array issue is why C /cannot/ detect array bounds infractions. It
> cannot depend on knowing more than the addres of element zero and the
> type of the array (which includes the type of the elements).
> I expect the C folks will be able to correct me. Hence I'm copying
> them this reply.
> Of course, there are other ways strings can be defined, even in C,
> with the right library sup****t.

I'm glad you included that last part.  Saved me the trouble of pointing
out that the only reason C still uses null terminated strings is momentum.
There are other ways, some of them in use on non-Unix systems.  And no
reason why a safer system could not be added to Unix, beyond momentum!

bill


-- 
Bill Gunshannon          |  de-moc-ra-cy (di mok' ra see) n.  Three wolves
billg999@[EMAIL PROTECTED]
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University of Scranton   |
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