Initialization of pointers

The initializer is an = (equal sign) followed by the expression that represents the address that the pointer is to contain. The following example defines the variables time and speed as having type double and amount as having type pointer to a double. The pointer amount is initialized to point to total:

double total, speed, *amount = &total;

The compiler converts an unsubscripted array name to a pointer to the first element in the array. You can assign the address of the first element of an array to a pointer by specifying the name of the array. The following two sets of definitions are equivalent. Both define the pointer student and initialize student to the address of the first element in section:

int section[80];
int *student = section;

is equivalent to:

int section[80];
int *student = &section[0];

You can assign the address of the first character in a string constant to a pointer by specifying the string constant in the initializer. The following example defines the pointer variable string and the string constant "abcd". The pointer string is initialized to point to the character a in the string "abcd".

char *string = "abcd";

The following example defines weekdays as an array of pointers to string constants. Each element points to a different string. The pointer weekdays[2], for example, points to the string "Tuesday".

static char *weekdays[ ] =
{
   "Sunday", "Monday", "Tuesday", "Wednesday",
   "Thursday", "Friday", "Saturday"
};

A pointer can also be initialized to null using any integer constant expression that evaluates to 0, for example char * a=0; Or with the nullptr keyword. Such a pointer is a null pointer. It does not point to any object.

The following examples define pointers with null pointer values:

char *a = 0; 
char *b = NULL;

C++ Beginning of C++11 only.

char *ch = nullptr;

C++ End of C++11 only.

Related information

Pointers