Command-line arguments are passed into programs using the arguments of main(). Here's a quick example, for a program called by typing

"progname file.txt 1 2.7":
#include
#include
using namespace std;
int main(int argc, char *argv[])
{
char *progname, *filename;
int value1;
float value2;
if (argc != 4) {
cerr << "usage: " << argv[0] << " file.txt int float" << endl;
exit(1);
}
progname = argv[0]; // argv[0] is the executable's name itself
filename = argv[1];
value1 = atoi(argv[2]); // convert C-string to int with atoi()
value2 = atof(argv[3]); // convert C-string to float with atof()
cout << progname << " " << filename << " " << value1 << " " << value2 <exit(0);
}