CODEWITHSUNDEEP
cpointers
Zahid Hossain
Zahid Hossain

Reputation: 302

Would it not be same memory address after this assignment?

int *p = NULL ,c , *q;
c=10;
p = &c;
q = p; 

printf ("%d and %d ",&p, &q );

Output: 

2686788 and 2686780

My question is: As far I assume, I thought the memory address will be same, as I have assigned p into q. May be I am wrong.

Upvotes: 3

Views: 140

Answers (4)

haccks
haccks

Reputation: 106012

p and q are two different variables and their addresses are different. &p and &q are addresses of p and q respectively.
The content of p and q will be the same, i.e. they will contain the same memory address after the assignment 

q = p;

p and q both are pointing to the same memory location now. As for the illustration this is shown in the below ASCII art:

          p                          
      +-------+                      
      |       |                 c    
0x200 | 0x100 +---------+   +-------+
      |       |         +-> |       |
      +-------+             |  10   |
          q             +-> |       |
      +-------+         |   +-------+
      |       |         |     0x100  
0x300 | 0x100 +---------+            
      |       |                      
      +-------+                      


        p = q but &p != &q

NOTE: To print the pointer data type use %p specifier in printf. 

 printf ("%p and %p ", (void *)&p, (void *)&q );

Upvotes: 15

dbush
dbush

Reputation: 223719

You're confusing the content of variables with their address. In this case the content of both p and q is the address of c. However, being distinct variables their addresses will always be different.

Upvotes: 2

Mr. Llama
Mr. Llama

Reputation: 20889

You are printing the address of the pointers themselves, not the pointer values:

// Prints the memory location of the pointers
printf ("%d and %d\n", &p, &q);

// Prints the values of the pointers
printf ("%d and %d\n",  p,  q);

// Prints the values that the pointers point to
printf ("%d and %d\n", *p, *q);

Upvotes: 1

dfranca
dfranca

Reputation: 5322

You are showing the address of the variable, not the address it's pointing to.

Both p and q are pointing to the same address, but are different variables, this way they've different addresses.

i.e:

c(address: 1000) -> 10

p(address: 1010) -> 1000

q(address: 2020) -> 1000

change to this, and you should see the value you want.

int *p = NULL ,c , *q;
c=10;
p = &c;
q = p; 

printf ("%p and %p ",p, q );

%p prints the address the pointer is pointing to.

Upvotes: 1

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