<refentry id="isalpha">
<refnamediv>
<refname>Isalpha</refname>
<refname>Isupper</refname>
<refname>Islower</refname>
<refname>Isdigit</refname>
<refname>Isalnum</refname>
<refname>Isspace</refname>
<refname>Ispunct</refname>
<refname>Isprint</refname>
<refname>Iscntrl</refname>
<refname>Isascii</refname>
<refpurpose>character classification</refpurpose>
</refnamediv>

<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>
#include &lt;ctype.h&gt;
</funcsynopsisinfo>

<funcprototype>
  <funcdef><function>isalpha</function></funcdef>
  <paramdef>int <parameter>c</parameter></paramdef>
</funcprototype>
</funcsynopsis>

</refsynopsisdiv>

<refsect1><title>Description</title>
<para>
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>