error in C++

Please try it :) :

void displayLine();
 
void main()
{
...
}
 
void displayLine()
{
...
}

I'll add one point to the correct responses by Nelek and Eugen Podsypalnikov that covered the error messages that you were getting. It should be int main() rather than void main(). For reference see here.[^]

this time i have tried to correct the code , and look what i get as the error; it says that missing function header (old-style formal list ?)

//this program demonstrates the use of function

#include <iostream>


using namespace std;

// function prototype
void displayLine ();

void main ();
{
	// Declare and initialized a Variable 
	float numberInput = 0,0;
	float numberSquared=0,0;
	float numberHalved =0,0;

	//emter input Item
	cout <<" Enter a number : ";
	cin >> numberInput ;

	//calculate the square of the number and the number halved 

	numberSquared = numberInput * numberInput ;
	numberHalved =  numberInput / 2 ;

	// Display the output items
	displayLine ();
	cout <<"Result of Calcutations : " << endl ;
	cout <<"Square of the Number : " << numberSquared << endl;
	cout <<"Half of the Number : " << numberHalved << endl;
	system("pause");
}  //end of main function 

//********* Programmer - defined function definitions *********

void displayLine ()
{
	cout <<" --------------------------- : " << endl;
} //end of displaying line function

You didn't fully follow the given suggestion, namely there is still a spurious semicolon in the following line

void main ();

please remove it and try again.

BTW don't add fake answers, modify instead the original post.
:)

first prob : correct third line

void displayLine();

2nd :
4th line
void main() (should not preceded with the ; at defination)

3rd:
5th, 6th, 7th line value initialization
float numberInput = 0.0f;(not 0,0 like u have done)
float numberSquared=0.0f;
float numberHalved =0.0f;


4th:
18th line
void displayLine ()(should not preceded with the ; at defination)

u must be careful with your basics enjoy :)