remedial ptr question

[technologist]

Why am I able to assign the value of 7 here:

#include<iostream>

using namespace std;
int main()
{
	int name = 12;
	int * n_ptr = &name;
	*n_ptr = 7;
	cout<<*n_ptr;

	return 0;
}

7

But not here?

int * n_ptr;
*n_ptr = 7;
cout<<* n_ptr;

run time error

[Peter87]

In your first code n_ptr is pointing to name so *n_ptr = 7; will assign the value 7 to name.

In your second code you have not told what n_ptr should point to so where are you trying to write the value 7? You can't be sure where n_ptr points to, but most probable is that it points to some memory location where your program is not allowed to write so that is why it crashes.

[technologist]

thx.

int * n_ptr = &name;

Are there any other valid structures n_ptr can point to besides &name?

[Peter87]

Not in your small program, but if you had other int objects in your program you could make it point to any of them.

[technologist]

...
thank you