void function

[Lee125]

Hello guys. can you explain to me?
why void function cannot be placed after main function?

 #include <iostream>

using namespace std;

const int WIDTH = 20;

int main() {
	int j, numRows;
	cout << "Enter number of rows: ";
	cin >> numRows;
	if (numRows > 0) {
		for (j = 0; j < numRows; j++) {
			drawLine('.', '-');
			drawLine('@', ' ');
		}
		drawLine('.', '-');	
	}
	
	system("PAUSE");
	return 0;
}

void drawLine(char ch1, char ch2) {
	int i;
	cout << ch1;
	for (i=0; i < WIDTH; i++)
		cout << ch2;
	cout << ch1 << endl;
}

[Yanson]

it can but you need to use a function prototype.

#include <iostream>

using namespace std;
void drawLine(char ch1, char ch2);

const int WIDTH = 20;

int main() {
	int j, numRows;
	cout << "Enter number of rows: ";
	cin >> numRows;
	if (numRows > 0) {
		for (j = 0; j < numRows; j++) {
			drawLine('.', '-');
			drawLine('@', ' ');
		}
		drawLine('.', '-');
	}

	system("PAUSE");
	return 0;
}

void drawLine(char ch1, char ch2) 
{
	int i;
	cout << ch1;
	for (i = 0; i < WIDTH; i++)
		cout << ch2;
	cout << ch1 << endl;
}

[Lee125]

oh ya i forget to put the function prototype.
Thanks Yanson.

Yanson , Should the function protoype must put in the sequence?

[S G H]

Yes, it must be "visible" at that point. Many reasons behind this, you will learn them while going deeper.

[Lee125]

why the function prototype look like different as usuall.
Can I know what is difference and how to use it.

#include <iostream>
#include <cstdlib>
#include <ctime>
#include "prog06.4b.h"

using namespace std;

int main() {
int generatedNum, guess;
generatedNum = generateNumber();
do {
guess = getGuess();
} while (!isCorrect(guess, generatedNum));

system("PAUSE");
return 0;
}

int generateNumber() {
srand((unsigned)time(0)); // seed the random generator
return (rand() % 100)+1; // generate a random number and return it
}

int getGuess() {
int number;
cout << "Enter a number between 1 and 100: ";
cin >> number;
return number;
}

bool isCorrect(int number_guess, int number_target) {
if (number_guess == number_target) {
cout << "Well done!" << endl;
return true;
}
else if (number_guess < number_target)
cout << "Higher!" << endl;
else
cout << "Lower!" << endl;
return false;
}

[AbstractionAnon]

why the function prototype look like different as usuall.
Can I know what is difference and how to use it.

The function prototype must match the function implementation exactly. Otherwise when the compiler encounters a call to your function, it will not know how to call your function because it has not seen yet.

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