Question

I’m playing with pointers and a can’t get why this declaration is fine

char *ptr = "Hey"

but this is wrong

int  *ptr = 10;

Can any one explain ?

Answer 1

The correct analogy would be that the following two are both wrong:

char * p = 'a';  // error
int  * q = 123;  // error

Here you are trying to assign a value of some type to a variable that is a pointer to a variable of that type.

By contrast, the following are correct:

int  tmp_a[] = { 10, 20, 30 };
char tmp_b[] = { 'h', 'e', 'l', 'l', 'o', '\0' };

int  * p = tmp_a;
char * q = tmp_b;

The string literal "hello" is an anonymous, read-only array of characters, of identical content as tmp_b, so it can be interpreted as a pointer to its first element. Since the character data is read-only, the correct definition should be this:

const char * r = "hello";  // r[0] - r[5] have the same value as q[0] - q[5]