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  26 <div class="titlepage"><div><div><h3 class="title">
  27 <a name="boost_asio.overview.rationale"></a><a class="link" href="rationale.html" title="Rationale">Rationale</a>
  28 </h3></div></div></div>
  29 <p>
  30         Most programs interact with the outside world in some way, whether it be
  31         via a file, a network, a serial cable, or the console. Sometimes, as is the
  32         case with networking, individual I/O operations can take a long time to complete.
  33         This poses particular challenges to application development.
  34       </p>
  35 <p>
  36         Boost.Asio provides the tools to manage these long running operations, without
  37         requiring programs to use concurrency models based on threads and explicit
  38         locking.
  39       </p>
  40 <p>
  41         The Boost.Asio library is intended for programmers using C++ for systems
  42         programming, where access to operating system functionality such as networking
  43         is often required. In particular, Boost.Asio addresses the following goals:
  44       </p>
  45 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
  46 <li class="listitem">
  47             <span class="bold"><strong>Portability.</strong></span> The library should support
  48             a range of commonly used operating systems, and provide consistent behaviour
  49             across these operating systems.
  50           </li>
  51 <li class="listitem">
  52             <span class="bold"><strong>Scalability.</strong></span> The library should facilitate
  53             the development of network applications that scale to thousands of concurrent
  54             connections. The library implementation for each operating system should
  55             use the mechanism that best enables this scalability.
  56           </li>
  57 <li class="listitem">
  58             <span class="bold"><strong>Efficiency.</strong></span> The library should support
  59             techniques such as scatter-gather I/O, and allow programs to minimise
  60             data copying.
  61           </li>
  62 <li class="listitem">
  63             <span class="bold"><strong>Model concepts from established APIs, such as BSD
  64             sockets.</strong></span> The BSD socket API is widely implemented and understood,
  65             and is covered in much literature. Other programming languages often
  66             use a similar interface for networking APIs. As far as is reasonable,
  67             Boost.Asio should leverage existing practice.
  68           </li>
  69 <li class="listitem">
  70             <span class="bold"><strong>Ease of use.</strong></span> The library should provide
  71             a lower entry barrier for new users by taking a toolkit, rather than
  72             framework, approach. That is, it should try to minimise the up-front
  73             investment in time to just learning a few basic rules and guidelines.
  74             After that, a library user should only need to understand the specific
  75             functions that are being used.
  76           </li>
  77 <li class="listitem">
  78             <span class="bold"><strong>Basis for further abstraction.</strong></span> The library
  79             should permit the development of other libraries that provide higher
  80             levels of abstraction. For example, implementations of commonly used
  81             protocols such as HTTP.
  82           </li>
  83 </ul></div>
  84 <p>
  85         Although Boost.Asio started life focused primarily on networking, its concepts
  86         of asynchronous I/O have been extended to include other operating system
  87         resources such as serial ports, file descriptors, and so on.
  88       </p>
  89 </div>
  90 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
  91 <td align="left"></td>
  92 <td align="right"><div class="copyright-footer">Copyright &#169; 2003-2017 Christopher M. Kohlhoff<p>
  93         Distributed under the Boost Software License, Version 1.0. (See accompanying
  94         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
  95       </p>
  96 </div></td>
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