- Recall that the expression
& xevaluates (returns) the address of the variable x
- In C++, you can
pass an address of a variable
as a parameter to a function
Example:
int main( int argc, char *argv[] ) { int x; f( &x ); // Pass the address of the int variable x as parameter ... }
- Naturally, in order to
receive an
address as value,
you need to define to
proper type of variable
- To receive (store) an address,
we must define a
reference (pointer) variable
as parameter
- Example:
void f ( int * a ) { // a can store an address of an int variable ... // The way to use the variable a is: *a }
- Consider the following program:
void f( int *a ) // No special & symbol... { *a = *a + 1; } int main(int argc, char *argv[]) { int x = 10; f( &x ); // Pass address of x cout << x; // ****** Prints 11 !!! }
- main() copies the
address of the variable
x into the
reference variable a of
the function f()
In other words: a points to the variable x of main()
- Therefore:
*a returns x !!!
- As a result:
*a = *a + 1 will update x in main() !!!
- Example Program:
(Demo above code)
- Prog file: click here