diff --git a/Makefile b/Makefile
index 52bacc6..0eca841 100644
--- a/Makefile
+++ b/Makefile
@@ -27,6 +27,7 @@ COMMON = \
 	 common.cc \
 	 c-camera.cc \
 	 c-filewatcher.cc \
+	 c-project.cc \
 	 c-utilities.cc \
 	 c-undo.cc \
 	 \
diff --git a/c-project.cc b/c-project.cc
new file mode 100644
index 0000000..82e219d
--- /dev/null
+++ b/c-project.cc
@@ -0,0 +1,57 @@
+#include "externals.hh"
+#include "c-project.hh"
+
+
+/*= A_ProjectPathListener ====================================================*/
+
+A_ProjectPathListener::~A_ProjectPathListener( ) {}
+
+
+/*= T_Project ================================================================*/
+
+void T_Project::setBasePath(
+		T_String const& path ) noexcept
+{
+	if ( !path || path[ path.length( ) - 1 ] != '/' ) {
+		setBasePathInternal( path );
+	} else {
+		setBasePathInternal( path.substr( 0 , path.length( ) - 1 ) );
+	}
+}
+
+void T_Project::setBasePathInternal(
+		T_String path ) noexcept
+{
+	if ( ( path && basePath_ == path )
+			|| ( !path && basePath_ == "." ) ) {
+		return;
+	}
+	if ( !path ) {
+		basePath_ = T_String::Pooled( "." );
+	} else {
+		basePath_ = std::move( path );
+	}
+
+	const auto n{ listeners_.size( ) };
+	for ( auto i = 0u ; i < n ; i ++ ) {
+		listeners_[ i ]->projectPathChanged( );
+	}
+}
+
+/*----------------------------------------------------------------------------*/
+
+T_String T_Project::pathOf(
+		T_String const& file ) const noexcept
+{
+	T_StringBuilder sb;
+	sb << basePath_ << '/' << file;
+	return std::move( sb );
+}
+
+T_String T_Project::pathOf(
+		char const* file ) const noexcept
+{
+	T_StringBuilder sb;
+	sb << basePath_ << '/' << file;
+	return std::move( sb );
+}
diff --git a/c-project.hh b/c-project.hh
new file mode 100644
index 0000000..2207b3e
--- /dev/null
+++ b/c-project.hh
@@ -0,0 +1,38 @@
+#pragma once
+#ifndef REAL_BUILD
+# include "externals.hh"
+#endif
+
+#include <ebcl/Sets.hh>
+
+
+class A_ProjectPathListener
+{
+    public:
+	virtual ~A_ProjectPathListener( ) = 0;
+	virtual void projectPathChanged( ) noexcept = 0;
+};
+
+struct T_Project
+{
+	void setBasePath( T_String const& path ) noexcept;
+
+	T_String const& basePath( ) const noexcept
+		{ return basePath_; }
+
+	T_String pathOf( T_String const& file ) const noexcept;
+	T_String pathOf( char const* file ) const noexcept;
+
+	void addListener( A_ProjectPathListener* listener ) noexcept
+		{ listeners_.add( listener ); }
+	void removeListener( A_ProjectPathListener* listener ) noexcept
+		{ listeners_.remove( listener ); }
+
+    private:
+	T_String basePath_{ T_String::Pooled( "." ) };
+	ebcl::T_Set< A_ProjectPathListener* > listeners_{
+		ebcl::UseTag< ebcl::ArrayBacked< 16 > >( )
+	};
+
+	void setBasePathInternal( T_String path ) noexcept;
+};