From e1a385ab400fa2082caddde001c8c9e1db0c1ded Mon Sep 17 00:00:00 2001
From: "Andrew M. Kuchling" <amk@amk.ca>
Date: Wed, 31 Aug 2005 13:50:17 +0000
Subject: Explain what file descriptors are; this change has been sitting in my
 tree for a while

---
 Doc/lib/libos.tex | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/Doc/lib/libos.tex b/Doc/lib/libos.tex
index dc621dd..2fbecfa 100644
--- a/Doc/lib/libos.tex
+++ b/Doc/lib/libos.tex
@@ -427,8 +427,15 @@ functions have a different order.
 
 \subsection{File Descriptor Operations \label{os-fd-ops}}
 
-These functions operate on I/O streams referred to
-using file descriptors.
+These functions operate on I/O streams referenced using file
+descriptors.  
+
+File descriptors are small integers corresponding to a file that has
+been opened by the current process.  For example, standard input is
+usually file descriptor 0, standard output is 1, and standard error is
+2.  Further files opened by a process will then be assigned 3, 4, 5,
+and so forth.  The name ``file descriptor'' is slightly deceptive; on
+{\UNIX} platforms, sockets and pipes are also referenced by file descriptors.
 
 
 \begin{funcdesc}{close}{fd}
-- 
cgit v0.12

