14.3 Pointer-Variable Declarations

The way to declare that a variable foo points to type t is

t *foo;

To remember this syntax, think “if you dereference foo, using the ‘*’ operator, what you get is type t. Thus, foo points to type t.”

Thus, we can declare variables that hold pointers to these three types, like this:

int *ptri;            /* Pointer to int. */
double *ptrd;         /* Pointer to double. */
double (*ptrda)[5];   /* Pointer to double[5]. */

‘int *ptri;’ means, “if you dereference ptri, you get an int.” ‘double (*ptrda)[5];’ means, “if you dereference ptrda, then subscript it by an integer less than 5, you get a double.” The parentheses express the point that you would dereference it first, then subscript it.

Contrast the last one with this:

double *aptrd[5];     /* Array of five pointers to double. */

Because ‘*’ has lower syntactic precedence than subscripting, ‘double *aptrd[5]’ means, “if you subscript aptrd by an integer less than 5, then dereference it, you get a double.” Therefore, *aptrd[5] declares an array of pointers, not a pointer to an array.