C++ allows us to call a function with out specifying all its arguments. In such cases, the function assigns a default value to the parameter which does not have a matching arguments in the function call.
Default values are specified when the function is declared .The compiler looks at the prototype to see how many arguments a function uses and alerts the program for possible default values.
Example:
void moveTo( int x = 0, int y = 0);
void moveTo( int = 0, int = 0);The function moveTo() can then be called with or without one or two arguments.
moveTo ();
moveTo (24);
moveTo(24, 50);One important point to note is that only the trailing arguments can have default values. That is, we must add default from right to left. We cannot provide a default to a particular argument in the middle of an argument list.
Example:
int mul(int i, int j=5,int k=10);//illegal
int mul(int i=0,int j,int k=10);//illegal
int mul(int i=5,int j); //illegal
int mul(int i=2,int j=5,int k=10);//illegalDefault arguments are useful in situation whose some arguments always have the some value. For example, bank interest may retain the same for all customers for a particular period of deposit.
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