--- a/docs/ccguide/isalpha.refentry	Fri Nov 15 21:49:51 2002 +0000
+++ b/docs/ccguide/isalpha.refentry	Fri Nov 15 21:49:51 2002 +0000
@@ -29,7 +29,70 @@
 
 <refsect1><title>Description</title>
 <para>
-Placeholder
+These functions use table look-up to classify characters
+according to their ascii value. The header file defines them
+as macros which means that they are implemented as fast, inline
+code rather than subroutines.
+</para>
+<para>
+Each results in non-zero for true or zero for false.
+</para>
+<para>
+The correct value is guaranteed for all integer values in
+isascii, but the result is unpredictable in the others if the
+argument is outside the range -1 to 127.
+</para>
+<para>
+The truth tested by each function is a follows:
 </para>
+<informaltable frame="none">
+<tgroup cols="2">
+<colspec colwidth="1in">
+<colspec colwidth="3in">
+<tbody>
+<row>
+<entry>isalpha</entry>
+<entry>c is a letter</entry>
+</row>
+<row>
+<entry>isdigit</entry>
+<entry>c is a digit</entry>
+</row>
+<row>
+<entry>isupper</entry>
+<entry>c is an upper case letter</entry>
+</row>
+<row>
+<entry>islower</entry>
+<entry>c is a lower case letter</entry>
+</row>
+<row>
+<entry>isalnum</entry>
+<entry>c is a letter or a digit</entry>
+</row>
+<row>
+<entry>isspace</entry>
+<entry>c is a space, tab character, newline, carriage return or formfeed</entry>
+</row>
+<row>
+<entry>iscntrl</entry>
+<entry>c is a control character (0 to 32) or DEL (127)</entry>
+</row>
+<row>
+<entry>ispunct</entry>
+<entry>c is neither countrol nor alpha-numeric</entry>
+</row>
+<row>
+<entry>isprint</entry>
+<entry>c is printable (32 to 126)</entry>
+</row>
+<row>
+<entry>isascii</entry>
+<entry>c is in the range -1 to 127</entry>
+</row>
+</tbody>
+</tgroup>
+</informaltable>
+
 </refsect1>
 </refentry>