Call the function by value in C ++

The method calls the function by the value of the parameters passed to a function that copies the actual value of a parameter into the official argument of the function. In this case, changes made to the parameter inside the function have no effect on the parameter.

By default, C ++ Language uses the call function by value to pass parameters. Under the general sense, the code inside a function cannot change the parameter used to call the function. Suppose the definition of the function traodoi () is as follows:

 // phan dinh nghia ham de trao doi cac gia tri. void traodoi ( int x , int y ) { int temp ; temp = x ; /* luu giu gia tri cua x */ x = y ; /* dat y vao trong x */ y = temp ; /* dat x vao trong y */ return ; } 

Now we call the function traodoi () by passing true values ​​like the following example:

 #include using namespace std ; // Phan khai bao ham void traodoi ( int x , int y ); int main () { // Khai bao bien cuc bo: int a = 100 ; int b = 200 ; cout << "Truoc khi trao doi, gia tri cua a la: " << a << endl ; cout << "Truoc khi trao doi, gia tri cua b la: " << b << endl ; // goi ham de trao doi cac gia tri. traodoi ( a , b ); cout << "Sau khi trao doi, gia tri cua a la: " << a << endl ; cout << "Sau khi trao doi, gia tri cua b la: " << b << endl ; return 0 ; } 

You put the above function definition at the end of this code, then compile and run the above C ++ program will produce the following result:

It indicates that there is no change in value even though they have been changed inside the function.

According to Tutorialspoint

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