diff --git a/sorting.h b/sorting.h
index d91ece3..95b6da5 100644
--- a/sorting.h
+++ b/sorting.h
@@ -35,7 +35,7 @@ typedef enum {
  * @param algorithm The sorting algorithm
  * @return The name of the algorithm.
  */
-<type> get_algorithm_name(<params>);
+char* get_algorithm_name(SortingAlgorithm algorithm);
 
 
 #ifdef LIST_VARIANT
@@ -64,7 +64,7 @@ void print_list(char* prefix, IntList list);
  * @param criterion The pointer to the function that implements the sorting criterion.
  * That function accepts two integer parameters and returns a boolean value.
  */
-void sort_list(<params>);
+void sort_list(IntList list, SortingAlgorithm algorithm, criterion_fn criterion);
 
 #else /* ARRAY_VARIANT */
 
diff --git a/stopwatch.c b/stopwatch.c
index 3c587c3..10c19d3 100644
--- a/stopwatch.c
+++ b/stopwatch.c
@@ -25,3 +25,71 @@
  *     -> seconds = ticks / CLOCK_PER_SEC
  *   microseconds are s * 10^-6
  */
+
+static clock_t start_time = 0;
+static clock_t passed_time = 0;
+static bool is_active = false;
+
+/**
+ * Starts taking the time. This function always starts at 0.
+ */
+void stopwatch_start()
+{
+    start_time = clock();
+    passed_time = 0;
+    is_active = true;
+}
+
+/**
+ * Stops or pauses taking the time. Time measurement can be resumed 
+ * via `stopwatch_resume`.
+ */
+void stopwatch_stop()
+{
+    if (!is_active) {
+        return;
+    }
+
+    passed_time += clock() - start_time;
+    is_active = false;
+}
+
+/**
+ * Resumes taking the time. The previously measured time value is
+ * used as start value.
+ */
+void stopwatch_resume()
+{
+    if (is_active) {
+        return;
+    }
+
+    start_time = clock();
+    is_active = true;
+}
+
+/**
+ * Determines whether or not the stopwatch takes the time.
+ * @return True if the stopwatch is measuring, false otherwise.
+ */
+bool stopwatch_is_active()
+{
+    return is_active;
+}
+
+/**
+ * The measured time in microseconds.
+ * 
+ * @return Either the processor time elapsed since start_stopwatch() has been called or
+ * the processor time elapsed between the calls of start_stopwatch() and stop_stopwatch().
+ */
+double stopwatch_get_elapsed_time()
+{
+    clock_t total_time = passed_time;
+    
+    if (is_active) {
+        total_time += clock() - start_time;
+    }
+    
+    return ((double)total_time / CLOCKS_PER_SEC) * 1000000.0;
+}
\ No newline at end of file