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In C, a byte of memory can be accessed using a pointer. A pointer containing the address of a variable is said to “point” to that variable.

Recall that when you declare a variable, a contiguous block of bytes is reserved in memory. A pointer to a variable is the address of the first of these bytes. A pointer can be created for every type of variable: be it primitive (for example int, char, or double), a custom data type created using a struct (we’ll cover those in a later lesson), or even another pointer. The syntax of a pointer is the following:

dataType* nameOfPointer;

or

dataType *nameOfPointer;

For example, to declare a pointer variable (called ptr) that points to an int, you would write:

int* ptr; // Pointer to an int int *ptr; // Same as above but different style.

In this case, ptr stores the address of the first byte of a block of memory containing an int. To print this address to the screen, printf() is used like so:

int* ptr; // Pointer to an int printf("%p", ptr); // %p needed to instruct printf that ptr is of type pointer.

This will output a hexadecimal integer that represents the address in memory that is storing a variable of type int. This number will be different every time the program is executed.

In later exercises, we will see how to use pointers.

Instructions

1.

Create a pointer variable called dblPtr that points to a variable of type double.

2.

Print the address stored in dblPtr to the screen.

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