diff --git a/gpio/gpio.c b/gpio/gpio.c
index 1186a65..447e53d 100644
--- a/gpio/gpio.c
+++ b/gpio/gpio.c
@@ -66,6 +66,9 @@ int wpMode ;
 char *usage = "Usage: gpio -v\n"
               "       gpio -h\n"
               "       gpio [-g|-1] ...\n"
+              "         where -g: pin numbering according to readall BCM column\n"
+              "         where -1: pin numbering according to readall Physical column\n"
+              "         when omitted: pin numbering according to readall wPi column\n"
               "       gpio [-d] ...\n"
               "       [-x extension:params] [[ -x ...]] ...\n"
               "       gpio [-p] <read/write/wb> ...\n"
@@ -73,6 +76,7 @@ char *usage = "Usage: gpio -v\n"
               "       gpio <toggle/blink> <pin>\n"
               "       gpio readall\n"
               "       gpio wfi <pin> <mode>\n"
+              "         where <mode> can be: rising, falling, both\n"
               "       gpio drive <group> <value>\n"
               "       gpio pwm-bal/pwm-ms \n"
               "       gpio pwmr <range> \n"