C++ Programming - Functions - Discussion

Parameters should not be initialized in the function argument.

float = Show(int, float) Function(Tmp);

Here While calling a function if another function is passed as parameter then that function should have values as parameter inside parenthesis not the data type.

int Function(int Tmp = Show());
or
int Function(int Tmp = Show(2,3.2));

Both are correct.

But
int Function(int Tmp = Show(int x , float y)); // Incorrect.

Function Prototype: A function prototype declares a function's name, return type, and parameter list. It informs the compiler about the function's existence and its signature.

Default Argument: A default argument is a value that is automatically assigned to a parameter if no argument is provided during the function call.  
In the given prototype:

int Function(int Tmp = Show()):
This declares a function named Function that returns an integer.

It takes an optional integer parameter Tmp. If no argument is provided for Tmp, the default value is obtained by calling the Show() function.

Why the other prototypes are invalid:
float Function(int Tmp = Show(int, float)):
The default argument Show(int, float) is incorrect. A default argument must be a constant expression or a function call that doesn't require any arguments.
float = Show(int, float) Function(Tmp);:

This is not a valid function prototype. It's syntactically incorrect and doesn't follow the standard function declaration format.

First know the logic's to execute.

First we should know the logic's to execute a program.

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[B]. float Function(int Tmp = Show(int, float));

In above option there is type but no arguments in show().

Actually the function definition is like this:

returntype funname(type arg1,type arg2) {
body
}
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[D]. float = Show(int, float) Function(Tmp);

in the above function also same error id there.

B is incorrect as how do we send the arguments of function show.

This is the case of the default argument, hence show should be like show (a, b) or show (2, 4.232), or such n such. But show (int, float) are data type that provide the default value to the function argument so give error. But show has no argument so possibly return some value if its definition has return.

Option A is correct as in a parameter any other parameter can not be passed.