Programming Tutorials

The indirection operator (*) - dereference operator.

By: Emiley J in C++ Tutorials on 2007-09-14  

The indirection operator (*) is also called the dereference operator. When a pointer is dereferenced, the value at the address stored by the pointer is retrieved.

Normal variables provide direct access to their own values. If you create a new variable of type unsigned short int called yourAge, and you want to assign the value in howOld to that new variable, you would write

unsigned short int yourAge;
yourAge = howOld;

A pointer provides indirect access to the value of the variable whose address it stores. To assign the value in howOld to the new variable yourAge by way of the pointer pAge, you would write

unsigned short int yourAge;
yourAge = *pAge;

The indirection operator (*) in front of the variable pAge means "the value stored at." This assignment says, "Take the value stored at the address in pAge and assign it to yourAge."

NOTE: The indirection operator (*) is used in two distinct ways with pointers: declaration and dereference. When a pointer is declared, the star indicates that it is a pointer, not a normal variable. For example,

unsigned short * pAge = 0; // make a pointer to an unsigned short

When the pointer is dereferenced, the indirection operator indicates that the value at the memory location stored in the pointer is to be accessed, rather than the address itself.

*pAge = 5; // assign 5 to the value at pAge

Also note that this same character (*) is used as the multiplication operator. The compiler knows which operator to call, based on context.

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