add explanation and copyright notice in the source file

1 files changed, 15 insertions, 1 deletions

diff --git a/gridcal.c b/gridcal.c
index 6e552b4..173f30c 100644
--- a/gridcal.c
+++ b/gridcal.c
@@ -3,9 +3,23 @@
 * Get two grid locators and compute the great-circle distance
 * between the centers of the two corresponding squares
 *
+* (c) Enzo "KatolaZ" Nicosia -- M0KTZ <m0ktz@katolaz.net>
 *
-* Usage: gridcal <grid1> [<grid2> [<pwr>]]
+* Usage: gridcal <loc1> [<loc2> [<pwr>]]
 *
+* If only one locator is provided, the program prints on output the 
+* latitude and longitude of the centre of the corresponding square, 
+* both in degrees and radians.
+*
+* If two locators are given, gridcal computes and prints the great-circle
+* distance between the two locators, in km and miles. If a third argument
+* is provided, it is interpreted as a power in Watts, and gridcal will 
+* print the distance in km and miles between the two locators, then the
+* power, and then the km/watt and the miles/watt
+*
+* This is free software. You can use, modify, distribute it under the 
+* terms of the ISC License. See LICENSE for details
+* 
 */
 
 #include <stdio.h>