diff --git a/src/Examples/StringExample.out b/src/Examples/StringExample.out
index 87170b8a9f7a26dc83846d5b518db2ba790a6ec7..61886792acbdb70945a2d05e0c731620e613d15f 100644
--- a/src/Examples/StringExample.out
+++ b/src/Examples/StringExample.out
@@ -5,7 +5,7 @@ str3: string
 str4: 28.4          //string type
 
 //functions
-size of string: 6 bytes
+size of string: 8 bytes
 alloc_size: 256
 memory: 512
 setter: Something new
diff --git a/src/TNL/FileName.h b/src/TNL/FileName.h
index adb9ce88d9c364572c8718363fbf5a0ed9fa59e7..601ced0426f26c9070551e0f95f00d0d1b07177f 100644
--- a/src/TNL/FileName.h
+++ b/src/TNL/FileName.h
@@ -40,18 +40,20 @@ class FileName
       void setFileNameBase( const String& fileNameBase );
 
       /// \brief Sets the extension of given file.
-      /// 
+      ///
       /// Sets \e extension as suffix of a file name.
-      /// @param extension String that specifies extension of file (without dot). Suffix of a file name. E.g. doc, xls, tnl.
+      /// @param extension String that specifies extension of file (without dot).
+      /// Suffix of a file name. E.g. doc, xls, tnl.
       void setExtension( const String& extension );
 
-      // \brief Sets index for given file.
+      /// \brief Sets index for given file.
       ///
       /// Sets \e index after the base name of given file.
-      /// @param index Integer - number of maximum 5(default) digits. (Number of digits can be changed with \c setDigitsCount).
+      /// @param index Integer - number of maximum 5(default) digits.
+      /// (Number of digits can be changed with \c setDigitsCount).
       void setIndex( const int index );
 
-      // \brief Sets number of digits for index of given file.
+      /// \brief Sets number of digits for index of given file.
       ///
       /// @param digitsCount Integer - number of digits.
       void setDigitsCount( const int digitsCount );
@@ -62,7 +64,7 @@ class FileName
       void setDistributedSystemNodeId( const Coordinates& nodeId );
       
       /// Creates appropriate name for given file.
-      /// 
+      ///
       /// Creates particular file name using \e fileNameBase, \e digitsCount,
       /// \e index and \e extension.
       String getFileName();
diff --git a/src/TNL/Timer.h b/src/TNL/Timer.h
index f885bdd443bbeeec0af8d496a7daf9c2193daa27..13567a438d84ba96e8ddfe934ebf3bd2c1ded104 100644
--- a/src/TNL/Timer.h
+++ b/src/TNL/Timer.h
@@ -15,32 +15,67 @@ namespace TNL {
 
 class Logger;
 
+/// \brief Class for time measuring
 class Timer
 {
    public:
- 
+
+      /////
+      /// \brief Basic constructor.
+      ///
+      /// This function creates a new timer.
       Timer();
 
+      /////
+      /// \brief Resets timer.
+      ///
+      /// Resets all time and cycle measurements such as real time, CPU time and CPU cycles.
+      /// Sets all of them to zero.
       void reset();
 
+      ////
+      /// \brief Stops timer.
+      ///
+      /// Stops all time and cycle measurements such as real time, CPU time and CPU cycles.
       void stop();
 
+      /////
+      /// \brief Starts timer.
+      ///
+      /// Starts all time and cycle measurements such as real time, CPU time and CPU cycles.
       void start();
 
+      /// \brief Counts the real (clock) time starting after the function \c start() is called.
       double getRealTime() const;
 
+      /////
+      /// \brief Measures the CPU time.
+      ///
+      /// CPU time is the time that measures how long it takes processor
+      /// to complete all computations.
       double getCPUTime() const;
 
+      /// Counts the number of CPU cycles (machine cycles).
       unsigned long long int getCPUCycles() const;
- 
+
+      /// \brief Writes a record to the \e logger.
+      ///
+      /// \param logger
+      /// \param logLevel
       bool writeLog( Logger& logger, int logLevel = 0 ) const;
  
    protected:
-      
+
+      /// Function for reading the real time from timer.
       double readRealTime() const;
 
+      /// \brief Function for reading the CPU time from timer.
+      ///
+      /// CPU time is the time that measures how long it takes processor
+      /// to complete all computations.
       double readCPUTime() const;
 
+      /// \brief Function for reading the number of CPU cycles (machine cycles).
       unsigned long long int readCPUCycles() const;
       
 
@@ -48,7 +83,10 @@ class Timer
           initialCPUTime, totalCPUTime;
  
    unsigned long long int initialCPUCycles, totalCPUCycles;
- 
+
+   /// \brief Saves information about state of the timer. 
+   ///
+   /// Knows whether the timer is currently stopped or not.
    bool stopState;
  
    inline unsigned long long rdtsc() const
diff --git a/src/UnitTests/FileNameTest.cpp b/src/UnitTests/FileNameTest.cpp
index 8819b609ce43ea7ec60d4caa6c3056790eff6b0c..5a69a1f2882d18f7a19928e70bd93c8586ecaefc 100644
--- a/src/UnitTests/FileNameTest.cpp
+++ b/src/UnitTests/FileNameTest.cpp
@@ -15,7 +15,7 @@
 #endif
 
 #include <TNL/FileName.h>
-#include <TNL/String.h>
+// #include <TNL/String.h>
 
 using namespace TNL;
 
@@ -71,6 +71,7 @@ TEST( FileNameTest, AllTogether )
     fname.setDigitsCount(3);
 
     EXPECT_EQ( fname.getFileName(), "name008.tnl" );
+    EXPECT_EQ( getFileExtension(fname.getFileName()), "tnl" );
 }
 #endif