fix option with cal

3_first_steps_in_a_terminal.md

@@ -71,18 +71,18 @@ When you launch a command, various things can happen:
 We can pass argument to the `cal` software the following way.
 
 ```sh
-cal -N
+cal -3
 ```
 
-What is the effect of the `-N` parameter ?
+What is the effect of the `-3` parameter ?
 
-You can add as many parameters as you want to your command, try `-N -C` what is the meaning of the `-C` parameter ?
+You can add as many parameters as you want to your command, try `-3 -1` what is the meaning of the `-1` parameter ?
 
 The `-H` option display the month of a given date in a `yyyy-mm-dd` format. Try to display your month of birth in vertical format.
 
 Traditionally, parameters are *named* which means that they are in the form of:
 
-* `-X` for an on/off option (like `cal -N`)
+* `-X` for an on/off option (like `cal -3`)
 * `-X something` for an input option (like `cal -H yyyy-mm-dd`)
 
 Here the name of the parameter is `X`, but software can also accept list of unnamed parameters. Try the following: