Question

#include <stdio.h>
#include <stdlib.h>

int main( void ) {
   char *ptr1 = "Hello World\n";
   char *ptr2;

   ptr2 = ptr1 + 6;
   ptr2 = "Test!\n";

   printf("%s",ptr2);
   printf("%s",ptr1);

   return EXIT_SUCCESS;   
}

Output:

Test!
Hello World

Why didn’t I get Hello Test!?
I thought id would overwrite the World-part from ptr1.

Answer 1

When you assign something to a pointer, such as ptr1 or ptr2. you are not changing the value of what is stored there, you are just changing what they point to.

When you say:

ptr2 = ptr1 + 6;

You are making ptr2 point to the 6th element of ptr1‘s string. Then you say:

ptr2 = "Test!\n";

This means ptr2 is now pointing to a new, different string, elsewhere in memory, which contains "Test!\n". So you have this:

ptr  ------->  "Hello World\n"
ptr2 ------->  "Test\n"

Now, when you print them, you get:

Test!
Hello World