Re: embedded questions!!!

On Fri, 13 Jan 2006 07:16:56 -0800 in comp.arch.embedded, "Richard
Henry" <rphenry@xxxxxxxx> wrote:

>
>"John B" <spamj_baraclough@xxxxxxxxxxxxxxxxxxx> wrote in message
>news:43c7b8d3$0$819$4c56ba96@xxxxxxxxxxxxxxxxxxxxxxxxx
>> On 12/01/2006 the venerable Chuck F. etched in runes:
[...]
>> The two declarations:
>>
>> char str1* = "JHONSON";
>>
>> and
>>
>> char str2[] = "JHONSON";
>>
>> both allocate space for a modifiable string. The difference being that the
>first one also creates a
>> pointer to that string.
>
>Isn't str2 also a pointer?

No.

Repeat after me: "Arrays are not pointers. Pointers are not arrays."
Despite what you may have been told.

A pointer is an object that references some other object.

An array is a group of contiguously allocated objects of the same
type.

(This is the important bit) The unadorned name of an array devolves
into a pointer to the first element of that array. Sort of like a
compile-time constant.

One point of confusion is the mechanism of array indexing. The syntax
"a[i]" has *exactly* the same meaning as "(*a + i)" whether a is a
pointer or array. So given the declarations above, str1[0] == 'J' ==
str2[0].

Another is the syntax for passing an array as a parameter to a
function. Thus "Fn(str1);" looks to be much the same as "Fn(str2);"
but the actual semantics are a bit different. Inside the function
itself, of course, the parameter is the same in either case.

>
>BTW, I will admit a recurring problem with understanding the nuances of C
>pointers.
>

Peter van der Linden's "Expert C Programming: Deep C Secrets" has one
or two excellent chapters on the differences between arrays and
pointers (as well as sections on understanding and contruction C
declarations, and other topics introductory books are to timid to
tackle). Somewhat dated (it was written about a dozen years ago), but
very readable and recommended. You don't read it because you're an
expert already, you read it to become expert...

Regards,
-=Dave

--
Change is inevitable, progress is not.
.

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