Re: Memory address and Pointer

erfan <zhaoerfan@xxxxxxxxx> writes:
vc++6.0,winxp.
I use this code to see the memory address and the real value`s
address below:
#include<stdio.h>
int main()
{
int a=22;
int *p;
int i;
p=&a;
printf("%x\n",&a);
printf("%p\n",*p);
}
the result is:
12ff7c
00000016
Press any key to continue

You're using incorrect formats in both your printf calls. "%x" prints
an unsigned int in hexadecimal; you're passing it a pointer to int.
"%p" expects a pointer, specifically a void*; you're passing it an
int.

the pointer p is pointing to a value which is 22,and the address of
the value is 0012ff7c.

Pointers point to objects, not to values; objects have values.

p points to an *object* whose value is 22. The address of that object
happens to be 0012ff7c (when displayed in hexadecimal).

i want to compare the memory address with the value address to see
wheather they are the same.

I don't know what you mean by "memory address" vs. "value address".

So ,next,i use win Debug to help me.
-d 0012:ff7c
but the output is 00 00 00 00 00 00 00 00 00......
what`s wrong? as far as i know,the value of a,must have it`s address
in the memory,and when i search the address,why there is nothing left
in it. there must be some mistake in my understanding,i really expect
your words~~

I've never used win Debug, so I can't help you with that.

Here's a corrected and expanded version of your program. I'm not sure
what you're asking, but perhaps this will help you answer it anyway.

#include <stdio.h>
int main(void)
{
int a = 22;
int *p = &a;
printf("a = %d\n", a);
printf("&a = %p\n", (void*)&a);
printf("p = %p\n", (void*)p);
printf("*p = %d\n", *p);
return 0;
}

--
Keith Thompson (The_Other_Keith) <kst-u@xxxxxxx>
Looking for software development work in the San Diego area.
"We must do something. This is something. Therefore, we must do this."
-- Antony Jay and Jonathan Lynn, "Yes Minister"
.

Relevant Pages

  • Re: object creation and naming at runtime?
    ... >>replaced with memory references by the compiler. ... I don't know where the computer will allocate space in ... memory for my int so I'll use a name for the address and let ... In the source code the pointer object (which will ...
    (alt.comp.lang.learn.c-cpp)
  • Re: 2-dimensional arrays and functions
    ... > int* foo ... >> that return memory addresses. ... >> You obviously don't know the difference between a pointer and a memory ... > address of the dynamically allocated memory is stored. ...
    (alt.comp.lang.learn.c-cpp)
  • Re: FIFO Problem
    ... text but a *pointer* to some text. ... pointing to the string in the clients memory. ... if you want to pass a string from one process to the other then ... int length; ...
    (comp.os.linux.development.apps)
  • Re: 2D array of structures
    ... Don't cast the return value of malloc(), ... you allocate here memory for 7 such structures. ... a pointer to the start of this memory, which is of type 'STRUCTURE *' ...
    (comp.lang.c)
  • Re: what is the purpose of C++ smart pointer
    ... pointer tracks the data it is referring to and updates itself ... following the changes of the memory it points to. ... How exactly will the smart pointer know that you moved the ... int * x = new int; ...
    (comp.os.linux.development.apps)