Make explicit that open doesn't return fd 0 or 1.

[pintos-anon] / doc / userprog.texi

diff --git a/doc/userprog.texi b/doc/userprog.texi
index 4d46b459033631b1c6851366f8286ca0c60944cf..59b198abdda810745fd6c5d950a5ceb8723c6378 100644 (file)
--- a/doc/userprog.texi
+++ b/doc/userprog.texi
@@ -453,7 +453,7 @@ parallel:
 
 @itemize
 @item
-Argument passing (@pxref{Argument Passing}).  Every user programs will
+Argument passing (@pxref{Argument Passing}).  Every user program will
 page fault immediately until argument passing is implemented.
 
 For now, you may simply wish to change
@@ -661,8 +661,12 @@ when the process exits or is terminated.
 
 File descriptors numbered 0 and 1 are reserved for the console: fd 0
 is standard input (@code{stdin}), fd 1 is standard output
-(@code{stdout}).  These special file descriptors are valid as system
-call arguments only as explicitly described below.
+(@code{stdout}).  The @code{open} system call will never return either
+of these file descriptors, which are valid as system call arguments only
+as explicitly described below.
+
+Each process has an independent set of file descriptors.  File
+descriptors are not inherited by child processes.
 
 Consider implementing this function in terms of @func{filesys_open}.
 @end deftypefn