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<H2>cin</H2>
<P><B>Library:</B>&nbsp;&nbsp;<A HREF="2-11.html">Input/output</A></P><UL>
<LI><A HREF="#sec1">Local Index</A></LI>
<LI><A HREF="#sec2">Summary</A></LI>
<LI><A HREF="#sec3">Synopsis</A></LI>
<LI><A HREF="#sec4">Description</A></LI>
<LI><A HREF="#sec5">Warnings</A></LI>
<LI><A HREF="#sec6">See Also</A></LI>
<LI><A HREF="#sec7">Standards Conformance</A></LI>
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<A NAME="sec1"><H3>Local Index</H3></A>
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<A NAME="sec2"><H3>Summary</H3></A>
<P>A predefined stream that controls input from a stream buffer associated with the object <SAMP>stdin</SAMP> declared in <SAMP>&lt;cstdio&gt;</SAMP></P>
<A NAME="sec3"><H3>Synopsis</H3></A>

<PRE>#include &lt;iostream&gt;

namespace std {
  extern istream cin;
}
</PRE>
<A NAME="sec4"><H3>Description</H3></A>
<P>The object <SAMP>cin</SAMP> controls input from a stream buffer associated with the object <SAMP>stdin</SAMP> declared in <SAMP>&lt;cstdio&gt;</SAMP>. By default, the standard C and C++ streams are synchronized, but you can improve performance by using the <B><I><A HREF="ios-base.html">ios_base</A></I></B> member function <SAMP>synch_with_stdio</SAMP> to desynchronize them.</P>
<P>After the object <SAMP>cin</SAMP> is initialized, <SAMP>cin.tie()</SAMP> returns <SAMP>&amp;cout</SAMP>, which implies that <SAMP>cin</SAMP> and <SAMP>cout</SAMP> are synchronized. </P>
<A NAME="sec5"><H3>Warnings</H3></A>
<P>Keep in mind that while the manipulator <SAMP>endl</SAMP> flushes the stream buffer, outputting the character <SAMP>'\n'</SAMP> is <I>not</I> guaranteed to flush the stream buffer. You should output  the <SAMP>'\n'</SAMP> character without <SAMP>endl</SAMP> only if you do not need the buffer flushed. Note that outputting the <SAMP>'\n'</SAMP> character in such cases, and hence not forcing a buffer flush, may result in a performance improvement. It greatly improves performance when C and C++ streams are not synchronized.</P>
<A NAME="sec6"><H3>See Also</H3></A>
<P><B><I><A HREF="basic-istream.html">basic_istream</A></I></B>, <B><I><A HREF="basic-iostream.html">basic_iostream</A></I></B>, <B><I><A HREF="basic-filebuf.html">basic_filebuf</A></I></B>, <B><I><A HREF="cout.html">cout</A></I></B>, <B><I><A HREF="cerr.html">cerr</A></I></B>, <B><I><A HREF="clog.html">clog</A></I></B>, <B><I><A HREF="wcin.html">wcin</A></I></B>, <B><I><A HREF="wcout.html">wcout</A></I></B>, <B><I><A HREF="wcerr.html">wcerr</A></I></B>, <B><I><A HREF="wclog.html">wclog</A></I></B>, <B><I><A HREF="ios-base.html">ios_base</A></I></B>, <B><I><A HREF="basic-ios.html">basic_ios</A></I></B></P>
<A NAME="sec7"><H3>Standards Conformance</H3></A>
<P><I>ISO/IEC 14882:1998 -- International Standard for Information Systems --Programming Language C++, Section 27.3.1</I></P>

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