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<h4 class="subsection">24.4.7 Atomic Data Access and Signal Handling</h4>

<p>Whether the data in your application concerns atoms, or mere text, you
have to be careful about the fact that access to a single datum is not
necessarily <dfn>atomic</dfn>.  This means that it can take more than one
instruction to read or write a single object.  In such cases, a signal
handler might be invoked in the middle of reading or writing the object.

   <p>There are three ways you can cope with this problem.  You can use data
types that are always accessed atomically; you can carefully arrange
that nothing untoward happens if an access is interrupted, or you can
block all signals around any access that had better not be interrupted
(see <a href="Blocking-Signals.html#Blocking-Signals">Blocking Signals</a>).

<ul class="menu">
<li><a accesskey="1" href="Non_002datomic-Example.html#Non_002datomic-Example">Non-atomic Example</a>: 		A program illustrating interrupted access. 
<li><a accesskey="2" href="Atomic-Types.html#Atomic-Types">Types</a>: 		Data types that guarantee no interruption. 
<li><a accesskey="3" href="Atomic-Usage.html#Atomic-Usage">Usage</a>: 		Proving that interruption is harmless. 
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