>> 1) pass by value (inother words : call by value)

> This is the usual way of passing arguments in C++.

>> 2) pass by reference (inother words: call by reference)

> This can be used in C++ with reference parameters.

>> 3) pass by value-result <- i have question this subject.

> C++ does not support value-result, but they can be simulated.

>> pass by value-result
>> passing mechanism
>> 1.The values of the arguments are copied into the formal parameters.
>> 2.The final values of the parameters are copied back out to the
>> arguments.
>> Characteristics of the Pass by Value-Result
>> -AKA copy-in , copy-out(copy-restore)
>> -no alias problem occurs(differ to the pass by reference in this
>> point)
>> -The order of copying the results may be important

>> ex)
>> Assume: pass by value-result
>> void square(int x,int y)
>> {
>>   x*=x;
>>   y*=y;
>> }

>> main()

> int main

>> {
>>    int a=5;
>>    int b=10;
>>    square(a,b);
>>    printf("a = %d b = %d\n",a,b);
>> }

> simulation in C++:
> void square(int &x, int &y)
> {
>   x *= x;
>   y *= y;
> }

> int main()
> {
>   int a = 5;
>   int b = 10;

>   // copy the arguments to temporaries, one per formal parameter.
>   int tmp1 = a;
>   int tmp2 = b;
>   // send these as references, so that result can be retrieved
>   square(tmp1, tmp2);
>   // copy result back:
>   a = tmp1;
>   b = tmp2;
>   printf("a = %d b = %d\n",a,b);
> }