Re: [cc65] c question

On Thu, May 27, 2010 at 02:32:47AM -0400, Chiron Bramberger wrote:
> What does the asterisk * in (byte*) mean? I know *p is a pointer,
> and I know &q would be an address, but what does it mean when the *
> is after something?

Actually this is wrong. *p is not a pointer. A pointer is declared by adding
the asterisk *after* a type. So

        unsigned* foo;

declares foo as a pointer to an unsigned. This is true for most other stuff,
too, so

        char const a = 3;

declares a constant character named a and assignes the value 3. The general
rule is that a qualifier (or asterisk) is applied to the type left of it. The
only exception for a qualifier is, if is on the left side (so there is no type
on the left), then it applies to the type on the right side. A more complex
example would be:

        unsigned const* volatile* bar;

which declares a volatile pointer to a pointer to a constant unsigned.

> In my textbook there's a second, similar example:
>
> typedef unsigned char BYTE;
> BYTE *p;
> p = (BYTE *) 0x1000; /* p contains address 0x1000 */

Using knowledge from above, this means:

* We declare the name "BYTE" for the type unsigned char.
* Then, we declare a pointer to a BYTE (an unsigned char).
* At last, we assign a value to the pointer. This value is the numerical
  value 0x1000, casted to a pointer to BYTE.
   
Regards


        Uz


-- 
Ullrich von Bassewitz                                  uz@musoftware.de
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