Update i/o README

03_inputs_and_outputs/README.md

 # Basic Input
 
-If you want to pass arguments to your program, you can add them to `main`.
+These examples illustrate command line arguments, and reading a file.
+
+```
+demo@linux:03_inputs_and_outputs$ make
+gcc -Wall -O3 -o add_integers add_integers.c
+gcc -Wall -O3 -o read_file read_file.c
+
+demo@linux:03_inputs_and_outputs$ ./add_integers 1 2
+1 + 2 = 3
+
+demo@linux:03_inputs_and_outputs$ ./read_file
+This text is in a file.
+```