X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;ds=sidebyside;f=doc%2Fuserprog.texi;h=59186129ca02ce05234a58f1f62f34dba5f081c6;hb=31d20882fdd5111d14b4e04a9b43da88d009b13c;hp=ff98074f8de198ea6465271848f573e7d5c73d7d;hpb=f13795ddcbe7ca6fc6c2f5329acb965d21575dfa;p=pintos-anon

diff --git a/doc/userprog.texi b/doc/userprog.texi
index ff98074..5918612 100644
--- a/doc/userprog.texi
+++ b/doc/userprog.texi
@@ -442,8 +442,8 @@ static inline bool put_user (uint8_t *udst, uint8_t byte) {
 
 Each of these functions assumes that the user address has already been
 verified to be below @code{PHYS_BASE}.  They also assume that you've
-modified @func{page_fault} so that a page fault in the kernel causes
-@code{eax} to be set to 0 and its former value copied into @code{eip}.
+modified @func{page_fault} so that a page fault in the kernel merely sets
+@code{eax} to 0 and copies its former value into @code{eip}.
 
 @node Project 2 Suggested Order of Implementation
 @section Suggested Order of Implementation
@@ -656,13 +656,16 @@ Consider implementing this function in terms of @func{filesys_remove}.
 @deftypefn {System Call} int open (const char *@var{file})
 Opens the file called @var{file}.  Returns a nonnegative integer handle
 called a ``file descriptor'' (fd), or -1 if the file could not be
-opened.  All open files associated with a process should be closed
-when the process exits or is terminated.
+opened.  
 
 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
@@ -728,7 +731,9 @@ Consider implementing this function in terms of @func{file_tell}.
 @end deftypefn
 
 @deftypefn {System Call} void close (int @var{fd})
-Closes file descriptor @var{fd}.
+Closes file descriptor @var{fd}.  
+Exiting or terminating a process implicitly closes all its open file
+descriptors, as if by calling this function for each one.
 
 Consider implementing this function in terms of @func{file_close}.
 @end deftypefn