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\part{Special files}
\textbf{This information is valid for Horde 4 only. See <a href="https://wiki.horde.org/Doc/Dev/SpecialFilesH3">Doc/Dev/SpecialFilesH3</a> for Horde 3 or <a href="https://wiki.horde.org/Doc/Dev/SpecialFiles">Doc/Dev/SpecialFiles</a> for Horde 5 and later.}

\begin{itemize}
\item \texttt{horde/lib/core.php}: This file
\begin{itemize}
\item sets some required PHP configuration settings


\item sets autoloading paths for Horde libraries


\item registers error handlers


\end{itemize}

\end{itemize}
There are several files with a special meaning that can be found in every Horde application:

\begin{itemize}
\item \texttt{index.php}: This script is loaded if a user enters an application. Usually this script doesn't have any functionality but simple loads the default view of the application, sometimes depending on the user's preferences.


\item \texttt{lib/Api.php}: This files defines and implements all methods that an application is exposing through the <a href="https://wiki.horde.org/Doc/Dev/Registry">Registry</a> to the other Horde applications and the Horde RPC servers.


\item \texttt{lib/Application.php}: This file defines information need to initialize the application and to interact with the Horde framework. It also defines the version number of the application.


\item \texttt{lib/Test.php}: This file defines any application specific tests to run when using the Horde test script.


\item \texttt{templates/common-header.inc}: This is the common page header template for all scripts of the application. All applications use the same page footer template \texttt{horde/templates/common-footer.inc}.


\item \texttt{themes/default/screen.css}: This is a CSS file that defines all application specific style sheet rules.


\end{itemize}
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