Value-based and reference-based calls in C/C ++

In many programming languages, call-by-value and call-by-reference methods are used to call functions ).

When a parameter is passed by value, a copy of the parameter value is generated and passed to the called function. The change of the copy does not affect the original variable value of the caller. This prevents unexpected side effects from affecting development correctness, reliable system. One disadvantage of calling by value is that if a large data item is passed, copying the data may take a long execution time.

 

By referencing the call, the caller allows the called function to directly access the caller's data and allow the called function to modify the data.

The reference call is advantageous to the performance and eliminates the overhead of assigning a large amount of data.

 

The following is an example of <C ++ University tutorial>:

 

# Include <cstdlib>

# Include <iostream>

 

Using namespace STD;

Int squarebyvalue (INT );
Void squarebyreference (Int &);

Int main (){
Int x = 2, Z = 4;
Cout <"x =" <x <"before squarebyvalue/N"
<"Value returned by squarebyvalue :"
<Squarebyvalue (x) <Endl
<"X =" <x <"after squarebyvalue/N" <Endl;
Cout <"z =" <z <"before squarebyreference" <Endl;
Squarebyreference (z );
Cout <"z =" <z <"after squarebyreference" <Endl;
Return 0;
}

Int squarebyvalue (int ){
Return a * =;
}

Void squarebyreference (Int & CREF ){
Cref * = CREF;
}