Passing an argument by value means that the method that receives the argument can not change the value of the argument. Passing an argument by reference means that the method that receives the argument can change the value of the incoming argument, and the argument may be changed in the orignal calling method.
Call_by_reference
That is called passing an argument by reference.
Strictly speaking, no. All arguments in C are passed by value. However, when the argument being passed is a memory address, although the address itself is passed by value, we're effectively passing the object that resides at that address -- by reference. Thus when a function's formal argument is a pointer variable (of any type), then it can be taken as read that the function is using the pass by reference semantic rather than the pass by value semantic. Nevertheless, it is important to keep in mind that the formal argument is assigned a copy of the actual argument and is therefore being passed by value.
Call by reference, particularly when applied to objects, because call by value automatically invokes an object's copy constructor, which is seldom desirable when passing objects into functions.
Default arguments are often considered to be optional arguments, however a default argument is only optional in the sense that the caller need not provide a value for it. The function must still instantiate the argument and must assign the appropriate value to it so, insofar as the function is concerned, the argument is not optional. To implement a function with a truly optional argument, we can define two overloads of that function, one that accepts the optional argument (without specifying a default value) and one that does not accept the argument. In this way we can define two different implementations, one that uses the argument and one that does not. void f (); // implementation that does not use the argument void f (int); // implementation that does use the argument In many cases, a default argument incurs no significant overhead over that of overloading. Thus we'd only use overloading to implement an optional argument where there is a significant overhead incurred by a default argument. Even so, we must also be aware that by eliminating the overhead within the function itself we may simply be passing that overhead back to the callers, because some or all of them would then have to decide which overload to call, resulting in code duplication that would likely be best handled by the function itself.
That is called passing an argument by value.
If you mean 'call by value' then, it means a method of passing argument to a function in c++. In this a copy of argument is passed to function and changes are not reflected.
If you do not include an optional argument, Excel will use the default value for that argument.
Call_by_reference
That is called passing an argument by reference.
Strictly speaking, no. All arguments in C are passed by value. However, when the argument being passed is a memory address, although the address itself is passed by value, we're effectively passing the object that resides at that address -- by reference. Thus when a function's formal argument is a pointer variable (of any type), then it can be taken as read that the function is using the pass by reference semantic rather than the pass by value semantic. Nevertheless, it is important to keep in mind that the formal argument is assigned a copy of the actual argument and is therefore being passed by value.
Where there is no need to return any type of value from a function
Call by reference, particularly when applied to objects, because call by value automatically invokes an object's copy constructor, which is seldom desirable when passing objects into functions.
Because you can produce fast and efficient code. Function arguments are passed "by value", and so you can't change the original value of the argument, but if you use pointers, you can.
Because you can produce fast and efficient code. Function arguments are passed "by value", and so you can't change the original value of the argument, but if you use pointers, you can.
Default arguments are often considered to be optional arguments, however a default argument is only optional in the sense that the caller need not provide a value for it. The function must still instantiate the argument and must assign the appropriate value to it so, insofar as the function is concerned, the argument is not optional. To implement a function with a truly optional argument, we can define two overloads of that function, one that accepts the optional argument (without specifying a default value) and one that does not accept the argument. In this way we can define two different implementations, one that uses the argument and one that does not. void f (); // implementation that does not use the argument void f (int); // implementation that does use the argument In many cases, a default argument incurs no significant overhead over that of overloading. Thus we'd only use overloading to implement an optional argument where there is a significant overhead incurred by a default argument. Even so, we must also be aware that by eliminating the overhead within the function itself we may simply be passing that overhead back to the callers, because some or all of them would then have to decide which overload to call, resulting in code duplication that would likely be best handled by the function itself.
Whenever you pass a value to a function, that value must be copied. If the value is large or complex, this can hinder performance, particularly when the function does not need to alter the value. To improve performance, we use the pass by reference semantic. Rather than passing the value itself, we pass the address of the value. That is, the address is copied, not the value. The function can then refer to the value by dereferencing the address. Ideally, pass by reference should only be used when the function does not need to alter the value. This is achieved by declaring the function's formal argument a pointer to constant type. This makes it clear to the caller the value of the actual argument will not be altered by the function. In some cases, we do require the function to alter the value. In these cases the argument is regarded as being an output parameter because it allows the function to return another value besides the return value. Typically, the caller will allocate some memory for the function to use (perhaps initialising it with a value), and then pass the address of that memory to the function. The function's formal argument is therefore declared a pointer to non-constant type, making it clear to the caller that the function will modify the value being pointed.