Week 4 Memory - Swap

Question

Does the = (assignment) get me a copy of the content or points me to the same location in memory? For some reason, I end up thinking that what the code does is not setting y = 44 in a separate memory location but rather point to x

#include <stdio.h>
#include <cs50.h>

int main(void)
{
    int x = 1;
    int y = 44;

    // Print Address and Value of x
    printf("%p\n",&x);
    printf("%i\n",x);

    // Print Address and Value of y
    printf("%p\n",&y);
    printf("%i\n",y);

    y = x;

    // Add Separator
    printf("------------------\n");

    printf("%p\n",&x);
    printf("%p\n",&y);

    if (x==y)
    {
        printf("YES\n");
    }
}

WHICH gives me the following on the command line

0x7fff5a5e8cb8 
1 
0x7fff5a5e8cb4 
44
------------------ 
0x7fff5a5e8cb8 
0x7fff5a5e8cb4 
YES

---

EDIT: I am noting a different behavior with Python. Once I set y=a I am getting the same memory location. When updating y I expected a to also change but that doesn't happen.

Answer 1

[EDIT: This applies to programming in the C language. See comments and question edit.]

The = operator copies values from one place to another. It matters what type of vars are being used.

That code does exactly what you said, `y=x;' takes the value stored in x and stores a copy of it in y. It does NOT change the address that y points to.

However, if x and y were (address) pointers instead of int variables, it would have copied the address stored in x and would have stored it in y. In this case, both address pointers would be pointing at the same memory location.

Confused yet? ;-)

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