diff --git a/src/dbg_tui.py b/src/dbg_tui.py
index 7239363..b3ecd4e 100644
--- a/src/dbg_tui.py
+++ b/src/dbg_tui.py
@@ -1,4 +1,5 @@
 from dpdebugger import Debugger
+from vm import VMException, VMExceptionType, VMStatus
 from dataclasses import dataclass
 from typing import cast
 import math
@@ -86,13 +87,41 @@ class DebuggerUI:
             user_input = self.commands_history[0]
         self.history_index = 0
         self.commands_history.appendleft("")
-        dbg_output = self.dbg.do_command(user_input.split())
-        self.terminal_panel.write(dbg_output)
+
+        try:
+            dbg_output = self.dbg.do_command(user_input.split())
+        except VMException as vme:
+            self._terminal_append(
+                    "VM Exception: " + vme.message
+                    )
+            return
+
+        # self._terminal_append(dbg_output)
+        self._terminal_append(dbg_output)
         self._display_source_lines()
         self.commands_history[0] = user_input
 
+    def _terminal_append(self, text: str):
+        self.terminal_panel.write(text)
+        viewport_height = self.terminal_panel.get_viewport_height()
+        contents = self.terminal_panel.get().split('\n')[-viewport_height:]
+        self.terminal_panel.set_text("\n".join(contents))
+
     def _display_source_lines(self):
-        active_line = self.dbg.get_current_source_line_number()
+        if self.dbg._vm.status == VMStatus.FINISHED:
+            return
+        try:
+            active_line = self.dbg.get_current_source_line_number()
+        except KeyError:
+            self._terminal_append(
+                    "Cant find source line your are on. "
+                    "May be you reached end of program. "
+                    )
+            self._terminal_append(
+                    "Please type \"reset\" to reset vm "
+                    "it's initial state"
+                    )
+            return
         lines = _get_source_lines(
                 srcline=active_line,
                 lines=self.srclines,