fixed output not found

src/output.cc

@@ -0,0 +1,17 @@
+#include "output.h"
+
+#include "constants.h"
+
+output::output():
+        contents{DISPLAY_BUFFER_SIZE, 0} {
+        for (int i = 0; i < DISPLAY_BUFFER_SIZE; ++i)
+                contents.push_back(0);
+}
+
+void output::clear() {
+        contents.clear();
+        contents.reserve(DISPLAY_BUFFER_SIZE);
+
+        for (int i = 0; i < DISPLAY_BUFFER_SIZE; ++i)
+                contents.push_back(0);
+}