What is the arguments in main when we don't pass anything?

Hi there,

I am now trialing the code below. It uses arguments supplied to the main function. I have no come across this before?
When I run the code it just displays :

usage: PR <filename>

argc=1 and arv has a sting the tells you the file location.

So where do the arguments come from?

Code:

#include <iostream>
#include<fstream>
using namespace std;

int main(int argc, char *argv[])
{
char ch;

if(argc!=2){
	cout << "usage: PR <filename>\n";
	return 1;
}

ifstream in(argv[1], ios::in |ios::binary);
if(!in){
cout << "Cannot open file.\n";
return 1;
}

while(in){
	in.get(ch);
	if(in) cout << ch;
}

	in.close();

	return 0;
}

 

Normally the running executable is the first param to main and you are only getting that.