--- a/docs/ccguide/chain.refentry	Thu Nov 14 03:55:12 2002 +0000
+++ b/docs/ccguide/chain.refentry	Fri Nov 15 21:49:51 2002 +0000
@@ -27,7 +27,25 @@
 
 <refsect1><title>Description</title>
 <para>
-Placeholder
+The action of F$CHAIN is described fully in the OS-9
+documentation. Chain implements the service request as
+described with one important exception: chain will NEVER return
+to the caller. If there is an error, the process will abort
+and return to its parent process. It might be wise, therefore,
+for the programs to check the existence and access permissions
+of the module before calling chain. Permissions may be checked
+by using "modlink()" or "modload()" followed by an "munlink()".
+</para>
+<para>
+"Modname" should point to the name of the desired module.
+"Paramsize is the length of the parameter string (which should
+normally be terminated with a "\n"), and "paramptr" points to
+the parameter string. "Type" is the module type as found in
+the module header (normally 1: program), and "lang" should
+match the language nibble in the module header (C programs
+have 1 for 6809 machine code here). "Datasize" may be zero, or
+it may contain the number of 256 byte pages to give to the new
+process as initial allocation of data memory.
 </para>
 </refsect1>
 </refentry>