diff --git a/android-app-core/res/layout/cpp_simple_app_button.xml b/android-app-core/res/layout/cpp_simple_app_button.xml
index 754fccce..2e5baf72 100644
--- a/android-app-core/res/layout/cpp_simple_app_button.xml
+++ b/android-app-core/res/layout/cpp_simple_app_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/appButton"
+        a:id="@id/cpp_button_app"
         a:src="@drawable/kb_logo"
         style="@style/cpp_simple_metro_control_image_button_style"
         a:contentDescription="App"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_clear_button.xml b/android-app-core/res/layout/cpp_simple_clear_button.xml
index 9e5a9e7b..fceee51b 100644
--- a/android-app-core/res/layout/cpp_simple_clear_button.xml
+++ b/android-app-core/res/layout/cpp_simple_clear_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/clearButton"
+        a:id="@id/cpp_button_clear"
         a:text="@string/c_clear"
         a:textStyle="bold"
         style="@style/cpp_simple_metro_control_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_copy_button.xml b/android-app-core/res/layout/cpp_simple_copy_button.xml
index 4c383d47..665276f2 100644
--- a/android-app-core/res/layout/cpp_simple_copy_button.xml
+++ b/android-app-core/res/layout/cpp_simple_copy_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/copyButton"
+        a:id="@id/cpp_button_copy"
         a:src="@drawable/kb_copy"
         style="@style/cpp_simple_metro_control_image_button_style"
         a:contentDescription="Copy"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_division_button.xml b/android-app-core/res/layout/cpp_simple_division_button.xml
index 24e67794..516c224e 100644
--- a/android-app-core/res/layout/cpp_simple_division_button.xml
+++ b/android-app-core/res/layout/cpp_simple_division_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/divisionButton"
+        a:id="@id/cpp_button_division"
         a:text="/"
         style="@style/cpp_simple_metro_blue_operation_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_dot_button.xml b/android-app-core/res/layout/cpp_simple_dot_button.xml
index 416fbefa..2607694e 100644
--- a/android-app-core/res/layout/cpp_simple_dot_button.xml
+++ b/android-app-core/res/layout/cpp_simple_dot_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/periodButton"
+        a:id="@id/cpp_button_period"
         a:text="."
         style="@style/metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_eight_digit_button.xml b/android-app-core/res/layout/cpp_simple_eight_digit_button.xml
index 345eae85..aa79844d 100644
--- a/android-app-core/res/layout/cpp_simple_eight_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_eight_digit_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/eightDigitButton"
+        a:id="@id/cpp_button_8"
         a:text="8"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_equals_button.xml b/android-app-core/res/layout/cpp_simple_equals_button.xml
index 204ffbf6..039d3321 100644
--- a/android-app-core/res/layout/cpp_simple_equals_button.xml
+++ b/android-app-core/res/layout/cpp_simple_equals_button.xml
@@ -7,6 +7,6 @@
   -->
 <Button
         xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/equalsButton"
+        a:id="@id/cpp_button_equals"
         a:text="="
         style="@style/cpp_simple_metro_control_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_erase_button.xml b/android-app-core/res/layout/cpp_simple_erase_button.xml
index bc22552b..389e6169 100644
--- a/android-app-core/res/layout/cpp_simple_erase_button.xml
+++ b/android-app-core/res/layout/cpp_simple_erase_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/eraseButton"
+        a:id="@id/cpp_button_erase"
         a:src="@drawable/kb_delete"
         style="@style/cpp_simple_metro_control_image_button_style"
         a:contentDescription="Erase"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_five_digit_button.xml b/android-app-core/res/layout/cpp_simple_five_digit_button.xml
index 48fa94f1..f7f9dae8 100644
--- a/android-app-core/res/layout/cpp_simple_five_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_five_digit_button.xml
@@ -6,6 +6,6 @@
   ~ or visit http://se.solovyev.org
   -->
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/fiveDigitButton"
+        a:id="@id/cpp_button_5"
         a:text="5"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_four_digit_button.xml b/android-app-core/res/layout/cpp_simple_four_digit_button.xml
index beeef1ec..a9e711a3 100644
--- a/android-app-core/res/layout/cpp_simple_four_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_four_digit_button.xml
@@ -6,6 +6,6 @@
   ~ or visit http://se.solovyev.org
   -->
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/fourDigitButton"
+        a:id="@id/cpp_button_4"
         a:text="4"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_functions_button.xml b/android-app-core/res/layout/cpp_simple_functions_button.xml
index f10d5054..bb441593 100644
--- a/android-app-core/res/layout/cpp_simple_functions_button.xml
+++ b/android-app-core/res/layout/cpp_simple_functions_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/functions_button"
+        a:id="@id/cpp_button_functions"
         a:text="ƒ(x)"
         a:textStyle="italic"
         style="@style/cpp_simple_metro_control_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_history_button.xml b/android-app-core/res/layout/cpp_simple_history_button.xml
index edeb6dfa..7ba3c30f 100644
--- a/android-app-core/res/layout/cpp_simple_history_button.xml
+++ b/android-app-core/res/layout/cpp_simple_history_button.xml
@@ -6,7 +6,7 @@
   ~ or visit http://se.solovyev.org
   -->
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/historyButton"
+        a:id="@id/cpp_button_history"
         a:text="@string/c_history_button"
         style="@style/cpp_simple_metro_control_button_style"
         a:textStyle="bold"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_left_button.xml b/android-app-core/res/layout/cpp_simple_left_button.xml
index 79d76cac..2f8c37a7 100644
--- a/android-app-core/res/layout/cpp_simple_left_button.xml
+++ b/android-app-core/res/layout/cpp_simple_left_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/leftButton"
+        a:id="@id/cpp_button_left"
         a:text="◀"
         style="@style/cpp_simple_metro_control_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_like_button.xml b/android-app-core/res/layout/cpp_simple_like_button.xml
index 1db2b59e..9d3eef7c 100644
--- a/android-app-core/res/layout/cpp_simple_like_button.xml
+++ b/android-app-core/res/layout/cpp_simple_like_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/likeButton"
+        a:id="@id/cpp_button_like"
         a:src="@drawable/kb_facebook"
         style="@style/cpp_simple_metro_control_image_button_style"
         a:contentDescription="Like"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_multiplication_button.xml b/android-app-core/res/layout/cpp_simple_multiplication_button.xml
index fcda5dcb..719decf3 100644
--- a/android-app-core/res/layout/cpp_simple_multiplication_button.xml
+++ b/android-app-core/res/layout/cpp_simple_multiplication_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/multiplicationButton"
+        a:id="@id/cpp_button_multiplication"
         a:text="×"
         style="@style/cpp_simple_metro_blue_operation_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_nine_digit_button.xml b/android-app-core/res/layout/cpp_simple_nine_digit_button.xml
index 6d5fa140..b01ac228 100644
--- a/android-app-core/res/layout/cpp_simple_nine_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_nine_digit_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/nineDigitButton"
+        a:id="@id/cpp_button_9"
         a:text="9"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_one_digit_button.xml b/android-app-core/res/layout/cpp_simple_one_digit_button.xml
index ccfd092f..9341718d 100644
--- a/android-app-core/res/layout/cpp_simple_one_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_one_digit_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/oneDigitButton"
+        a:id="@id/cpp_button_1"
         a:text="1"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_paste_button.xml b/android-app-core/res/layout/cpp_simple_paste_button.xml
index 42eca36f..b9695e12 100644
--- a/android-app-core/res/layout/cpp_simple_paste_button.xml
+++ b/android-app-core/res/layout/cpp_simple_paste_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/pasteButton"
+        a:id="@id/cpp_button_paste"
         a:src="@drawable/kb_paste"
         style="@style/cpp_simple_metro_control_image_button_style"
         a:contentDescription="Paste"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_percent_button.xml b/android-app-core/res/layout/cpp_simple_percent_button.xml
index d91ed8b3..b98f7063 100644
--- a/android-app-core/res/layout/cpp_simple_percent_button.xml
+++ b/android-app-core/res/layout/cpp_simple_percent_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/percentButton"
+        a:id="@id/cpp_button_percent"
         a:text="%"
         style="@style/cpp_simple_metro_blue_operation_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_plus_button.xml b/android-app-core/res/layout/cpp_simple_plus_button.xml
index c41001bf..0c10bb7b 100644
--- a/android-app-core/res/layout/cpp_simple_plus_button.xml
+++ b/android-app-core/res/layout/cpp_simple_plus_button.xml
@@ -6,6 +6,6 @@
   ~ or visit http://se.solovyev.org
   -->
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/plusButton"
+        a:id="@id/cpp_button_plus"
         a:text="+"
         style="@style/cpp_simple_metro_blue_operation_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_power_button.xml b/android-app-core/res/layout/cpp_simple_power_button.xml
index 5f77f94c..f6a5f95b 100644
--- a/android-app-core/res/layout/cpp_simple_power_button.xml
+++ b/android-app-core/res/layout/cpp_simple_power_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/powerButton"
+        a:id="@id/cpp_button_power"
         a:text="^"
         style="@style/cpp_simple_metro_blue_operation_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_right_button.xml b/android-app-core/res/layout/cpp_simple_right_button.xml
index 4656d89d..bc24d176 100644
--- a/android-app-core/res/layout/cpp_simple_right_button.xml
+++ b/android-app-core/res/layout/cpp_simple_right_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/rightButton"
+        a:id="@id/cpp_button_right"
         a:text="▶"
         style="@style/cpp_simple_metro_control_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_round_brackets_button.xml b/android-app-core/res/layout/cpp_simple_round_brackets_button.xml
index 1ae049d9..9833ee95 100644
--- a/android-app-core/res/layout/cpp_simple_round_brackets_button.xml
+++ b/android-app-core/res/layout/cpp_simple_round_brackets_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/roundBracketsButton"
+        a:id="@id/cpp_button_round_brackets"
         a:text="()"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_settings_button.xml b/android-app-core/res/layout/cpp_simple_settings_button.xml
index df6e4293..f4c13728 100644
--- a/android-app-core/res/layout/cpp_simple_settings_button.xml
+++ b/android-app-core/res/layout/cpp_simple_settings_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/settingsButton"
+        a:id="@id/cpp_button_settings"
         a:src="@drawable/kb_settings"
         style="@style/cpp_simple_metro_control_image_button_style"
         a:contentDescription="Settings"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_seven_digit_button.xml b/android-app-core/res/layout/cpp_simple_seven_digit_button.xml
index a45fae6a..3ef824aa 100644
--- a/android-app-core/res/layout/cpp_simple_seven_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_seven_digit_button.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/sevenDigitButton"
+        a:id="@id/cpp_button_7"
         a:text="7"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_six_digit_button.xml b/android-app-core/res/layout/cpp_simple_six_digit_button.xml
index aef39320..63d57149 100644
--- a/android-app-core/res/layout/cpp_simple_six_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_six_digit_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/sixDigitButton"
+        a:id="@id/cpp_button_6"
         a:text="6"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_subtraction_button.xml b/android-app-core/res/layout/cpp_simple_subtraction_button.xml
index b5888abc..78a9d36f 100644
--- a/android-app-core/res/layout/cpp_simple_subtraction_button.xml
+++ b/android-app-core/res/layout/cpp_simple_subtraction_button.xml
@@ -6,6 +6,6 @@
   ~ or visit http://se.solovyev.org
   -->
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/subtractionButton"
+        a:id="@id/cpp_button_subtraction"
         a:text="-"
         style="@style/cpp_simple_metro_blue_operation_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_three_digit_button.xml b/android-app-core/res/layout/cpp_simple_three_digit_button.xml
index 9cc9c46f..357a13f2 100644
--- a/android-app-core/res/layout/cpp_simple_three_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_three_digit_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/threeDigitButton"
+        a:id="@id/cpp_button_3"
         a:text="3"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_two_digit_button.xml b/android-app-core/res/layout/cpp_simple_two_digit_button.xml
index 5745a27d..eb884305 100644
--- a/android-app-core/res/layout/cpp_simple_two_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_two_digit_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/twoDigitButton"
+        a:id="@id/cpp_button_2"
         a:text="2"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_vars_button.xml b/android-app-core/res/layout/cpp_simple_vars_button.xml
index 6be475f1..0bea581e 100644
--- a/android-app-core/res/layout/cpp_simple_vars_button.xml
+++ b/android-app-core/res/layout/cpp_simple_vars_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/vars_button"
+        a:id="@id/cpp_button_vars"
         a:text="π,…"
         a:textStyle="italic"
         style="@style/cpp_simple_metro_control_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/layout/cpp_simple_zero_digit_button.xml b/android-app-core/res/layout/cpp_simple_zero_digit_button.xml
index 4da0706c..37867e1f 100644
--- a/android-app-core/res/layout/cpp_simple_zero_digit_button.xml
+++ b/android-app-core/res/layout/cpp_simple_zero_digit_button.xml
@@ -7,6 +7,6 @@
   -->
 
 <Button xmlns:a="http://schemas.android.com/apk/res/android"
-        a:id="@+id/zeroDigitButton"
+        a:id="@id/cpp_button_0"
         a:text="0"
         style="@style/cpp_simple_metro_digit_button_style"/>
\ No newline at end of file
diff --git a/android-app-core/res/values/ids.xml b/android-app-core/res/values/ids.xml
index bc3359c4..c44a23fe 100644
--- a/android-app-core/res/values/ids.xml
+++ b/android-app-core/res/values/ids.xml
@@ -1,36 +1,37 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-    <item type="id" name="oneDigitButton"/>
-    <item type="id" name="twoDigitButton"/>
-    <item type="id" name="threeDigitButton"/>
-    <item type="id" name="fourDigitButton"/>
-    <item type="id" name="fiveDigitButton"/>
-    <item type="id" name="sixDigitButton"/>
-    <item type="id" name="sevenDigitButton"/>
-    <item type="id" name="eightDigitButton"/>
-    <item type="id" name="nineDigitButton"/>
-    <item type="id" name="zeroDigitButton"/>
+    <item type="id" name="cpp_button_1"/>
+    <item type="id" name="cpp_button_2"/>
+    <item type="id" name="cpp_button_3"/>
+    <item type="id" name="cpp_button_4"/>
+    <item type="id" name="cpp_button_5"/>
+    <item type="id" name="cpp_button_6"/>
+    <item type="id" name="cpp_button_7"/>
+    <item type="id" name="cpp_button_8"/>
+    <item type="id" name="cpp_button_9"/>
+    <item type="id" name="cpp_button_0"/>
 
-    <item type="id" name="periodButton"/>
-    <item type="id" name="roundBracketsButton"/>
-    <item type="id" name="settingsButton"/>
-    <item type="id" name="likeButton"/>
-    <item type="id" name="leftButton"/>
-    <item type="id" name="rightButton"/>
-    <item type="id" name="vars_button"/>
-    <item type="id" name="functions_button"/>
-    <item type="id" name="appButton"/>
-    <item type="id" name="historyButton"/>
-    <item type="id" name="multiplicationButton"/>
-    <item type="id" name="divisionButton"/>
-    <item type="id" name="plusButton"/>
-    <item type="id" name="subtractionButton"/>
-    <item type="id" name="percentButton"/>
-    <item type="id" name="powerButton"/>
-    <item type="id" name="clearButton"/>
-    <item type="id" name="eraseButton"/>
-    <item type="id" name="copyButton"/>
-    <item type="id" name="pasteButton"/>
-    <item type="id" name="equalsButton"/>
+    <item type="id" name="cpp_button_period"/>
+    <item type="id" name="cpp_button_round_brackets"/>
+    <item type="id" name="cpp_button_settings"/>
+    <item type="id" name="cpp_button_like"/>
+    <item type="id" name="cpp_button_left"/>
+    <item type="id" name="cpp_button_right"/>
+    <item type="id" name="cpp_button_vars"/>
+    <item type="id" name="cpp_button_functions"/>
+    <item type="id" name="cpp_button_operators"/>
+    <item type="id" name="cpp_button_app"/>
+    <item type="id" name="cpp_button_history"/>
+    <item type="id" name="cpp_button_multiplication"/>
+    <item type="id" name="cpp_button_division"/>
+    <item type="id" name="cpp_button_plus"/>
+    <item type="id" name="cpp_button_subtraction"/>
+    <item type="id" name="cpp_button_percent"/>
+    <item type="id" name="cpp_button_power"/>
+    <item type="id" name="cpp_button_clear"/>
+    <item type="id" name="cpp_button_erase"/>
+    <item type="id" name="cpp_button_copy"/>
+    <item type="id" name="cpp_button_paste"/>
+    <item type="id" name="cpp_button_equals"/>
 
 </resources>
\ No newline at end of file
diff --git a/android-app-core/src/main/java/org/solovyev/android/calculator/CalculatorButton.java b/android-app-core/src/main/java/org/solovyev/android/calculator/CalculatorButton.java
index f20a5555..0812ce4d 100644
--- a/android-app-core/src/main/java/org/solovyev/android/calculator/CalculatorButton.java
+++ b/android-app-core/src/main/java/org/solovyev/android/calculator/CalculatorButton.java
@@ -16,47 +16,47 @@ import java.util.Map;
 public enum CalculatorButton {
 
     /*digits*/
-    one(R.id.oneDigitButton, "1"),
-    two(R.id.twoDigitButton, "2"),
-    three(R.id.threeDigitButton, "3"),
-    four(R.id.fourDigitButton, "4"),
-    five(R.id.fiveDigitButton, "5"),
-    six(R.id.sixDigitButton, "6"),
-    seven(R.id.sevenDigitButton, "7"),
-    eight(R.id.eightDigitButton, "8"),
-    nine(R.id.nineDigitButton, "9"),
-    zero(R.id.zeroDigitButton, "0"),
+    one(R.id.cpp_button_1, "1"),
+    two(R.id.cpp_button_2, "2"),
+    three(R.id.cpp_button_3, "3"),
+    four(R.id.cpp_button_4, "4"),
+    five(R.id.cpp_button_5, "5"),
+    six(R.id.cpp_button_6, "6"),
+    seven(R.id.cpp_button_7, "7"),
+    eight(R.id.cpp_button_8, "8"),
+    nine(R.id.cpp_button_9, "9"),
+    zero(R.id.cpp_button_0, "0"),
 
-    period(R.id.periodButton, "."),
-    brackets(R.id.roundBracketsButton, "()"),
+    period(R.id.cpp_button_period, "."),
+    brackets(R.id.cpp_button_round_brackets, "()"),
 
-    settings(R.id.settingsButton, CalculatorSpecialButton.settings_detached),
-    like(R.id.likeButton, CalculatorSpecialButton.like),
+    settings(R.id.cpp_button_settings, CalculatorSpecialButton.settings_detached),
+    like(R.id.cpp_button_like, CalculatorSpecialButton.like),
 
     /*last row*/
-    left(R.id.leftButton, CalculatorSpecialButton.cursor_left),
-    right(R.id.rightButton, CalculatorSpecialButton.cursor_right),
-    vars(R.id.vars_button, CalculatorSpecialButton.vars_detached),
-    functions(R.id.functions_button, CalculatorSpecialButton.functions_detached),
-    app(R.id.appButton, CalculatorSpecialButton.open_app),
-    history(R.id.historyButton, CalculatorSpecialButton.history_detached),
+    left(R.id.cpp_button_left, CalculatorSpecialButton.cursor_left),
+    right(R.id.cpp_button_right, CalculatorSpecialButton.cursor_right),
+    vars(R.id.cpp_button_vars, CalculatorSpecialButton.vars_detached),
+    functions(R.id.cpp_button_functions, CalculatorSpecialButton.functions_detached),
+    app(R.id.cpp_button_app, CalculatorSpecialButton.open_app),
+    history(R.id.cpp_button_history, CalculatorSpecialButton.history_detached),
 
     /*operations*/
-    multiplication(R.id.multiplicationButton, "*"),
-    division(R.id.divisionButton, "/"),
-    plus(R.id.plusButton, "+"),
-    subtraction(R.id.subtractionButton, "-"),
-    percent(R.id.percentButton, "%"),
-    power(R.id.powerButton, "^"),
+    multiplication(R.id.cpp_button_multiplication, "*"),
+    division(R.id.cpp_button_division, "/"),
+    plus(R.id.cpp_button_plus, "+"),
+    subtraction(R.id.cpp_button_subtraction, "-"),
+    percent(R.id.cpp_button_percent, "%"),
+    power(R.id.cpp_button_power, "^"),
 
     /*last column*/
-    clear(R.id.clearButton, CalculatorSpecialButton.clear),
-    erase(R.id.eraseButton, CalculatorSpecialButton.erase, CalculatorSpecialButton.clear),
-    copy(R.id.copyButton, CalculatorSpecialButton.copy),
-    paste(R.id.pasteButton, CalculatorSpecialButton.paste),
+    clear(R.id.cpp_button_clear, CalculatorSpecialButton.clear),
+    erase(R.id.cpp_button_erase, CalculatorSpecialButton.erase, CalculatorSpecialButton.clear),
+    copy(R.id.cpp_button_copy, CalculatorSpecialButton.copy),
+    paste(R.id.cpp_button_paste, CalculatorSpecialButton.paste),
 
     /*equals*/
-    equals(R.id.equalsButton, CalculatorSpecialButton.equals);
+    equals(R.id.cpp_button_equals, CalculatorSpecialButton.equals);
 
 
     private final int buttonId;
diff --git a/android-app-core/src/main/java/org/solovyev/android/calculator/CalculatorButtons.java b/android-app-core/src/main/java/org/solovyev/android/calculator/CalculatorButtons.java
index f743045f..03bdc8d4 100644
--- a/android-app-core/src/main/java/org/solovyev/android/calculator/CalculatorButtons.java
+++ b/android-app-core/src/main/java/org/solovyev/android/calculator/CalculatorButtons.java
@@ -53,14 +53,14 @@ public final class CalculatorButtons {
     }
 
     static void initMultiplicationButton(@NotNull View root) {
-        final View multiplicationButton = root.findViewById(R.id.multiplicationButton);
+        final View multiplicationButton = root.findViewById(R.id.cpp_button_multiplication);
         if ( multiplicationButton instanceof Button) {
             ((Button) multiplicationButton).setText(Locator.getInstance().getEngine().getMultiplicationSign());
         }
     }
 
     public static void initMultiplicationButton(@NotNull RemoteViews views) {
-        views.setTextViewText(R.id.multiplicationButton, Locator.getInstance().getEngine().getMultiplicationSign());
+        views.setTextViewText(R.id.cpp_button_multiplication, Locator.getInstance().getEngine().getMultiplicationSign());
     }
 
 
@@ -75,7 +75,7 @@ public final class CalculatorButtons {
             if (AndroidUtils.getScreenOrientation(activity) == Configuration.ORIENTATION_PORTRAIT
                     || !CalculatorPreferences.Gui.autoOrientation.getPreference(preferences)) {
 
-                final DragButton equalsButton = (DragButton)activity.findViewById(R.id.equalsButton);
+                final DragButton equalsButton = (DragButton)activity.findViewById(R.id.cpp_button_equals);
                 if (equalsButton != null) {
                     if (CalculatorPreferences.Gui.showEqualsButton.getPreference(preferences)) {
                         equalsButton.setVisibility(View.VISIBLE);
diff --git a/android-app/res/layout/calc_clear_button.xml b/android-app/res/layout/calc_clear_button.xml
index 6b84b546..d6ef49d3 100644
--- a/android-app/res/layout/calc_clear_button.xml
+++ b/android-app/res/layout/calc_clear_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.calculator.view.NumeralBasesButton xmlns:a="http://schemas.android.com/apk/res/android"
 			 xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-			 a:id="@+id/clearButton"
+			 a:id="@id/cpp_button_clear"
 			 c:textUp="dec"
 			 a:text="@string/c_clear"
 			 c:textDown="bin"
diff --git a/android-app/res/layout/calc_copy_button.xml b/android-app/res/layout/calc_copy_button.xml
index d0fe8181..62132a7d 100644
--- a/android-app/res/layout/calc_copy_button.xml
+++ b/android-app/res/layout/calc_copy_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-			 a:id="@+id/copyButton"
+			 a:id="@id/cpp_button_copy"
 			 a:src="@drawable/kb_copy"
 			 style="?cpp_control_image_button_style"
 			 a:onClick="copyButtonClickHandler"/>
\ No newline at end of file
diff --git a/android-app/res/layout/calc_division_button.xml b/android-app/res/layout/calc_division_button.xml
index 05755043..e44543c9 100644
--- a/android-app/res/layout/calc_division_button.xml
+++ b/android-app/res/layout/calc_division_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/divisionButton"
+													   a:id="@id/cpp_button_division"
 													   c:textUp="%"
 													   a:text="/"
 													   c:textDown="√"
diff --git a/android-app/res/layout/calc_donate_button.xml b/android-app/res/layout/calc_donate_button.xml
index ad4c928b..b55b7e6e 100644
--- a/android-app/res/layout/calc_donate_button.xml
+++ b/android-app/res/layout/calc_donate_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-			 a:id="@+id/likeButton"
+			 a:id="@id/cpp_button_like"
 			 a:src="@drawable/kb_facebook"
 			 style="?cpp_control_image_button_style"
 			 a:onClick="likeButtonClickHandler"/>
\ No newline at end of file
diff --git a/android-app/res/layout/calc_dot_button.xml b/android-app/res/layout/calc_dot_button.xml
index a006ef05..cb85e707 100644
--- a/android-app/res/layout/calc_dot_button.xml
+++ b/android-app/res/layout/calc_dot_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/periodButton"
+													   a:id="@id/cpp_button_period"
 													   a:text="."
 													   c:textUp=","
 													   c:directionTextScale="0.5"
diff --git a/android-app/res/layout/calc_eight_digit_button.xml b/android-app/res/layout/calc_eight_digit_button.xml
index bec911cf..fe59019f 100644
--- a/android-app/res/layout/calc_eight_digit_button.xml
+++ b/android-app/res/layout/calc_eight_digit_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/eightDigitButton" a:text="8"
+													   a:id="@id/cpp_button_8" a:text="8"
 													   c:textUp="ln"
 													   c:textLeft="0d:"
 													   c:textDown="lg"
diff --git a/android-app/res/layout/calc_equals_button.xml b/android-app/res/layout/calc_equals_button.xml
index ca375116..e000acf0 100644
--- a/android-app/res/layout/calc_equals_button.xml
+++ b/android-app/res/layout/calc_equals_button.xml
@@ -8,7 +8,7 @@
 <org.solovyev.android.view.drag.DirectionDragButton
 		xmlns:a="http://schemas.android.com/apk/res/android"
 		xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-		a:id="@+id/equalsButton"
+		a:id="@id/cpp_button_equals"
 		c:textUp="≡"
 		a:text="="
 		c:directionTextScale="0.5"
diff --git a/android-app/res/layout/calc_erase_button.xml b/android-app/res/layout/calc_erase_button.xml
index 46ad2dfd..f0ce3c6e 100644
--- a/android-app/res/layout/calc_erase_button.xml
+++ b/android-app/res/layout/calc_erase_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-			 a:id="@+id/eraseButton"
+			 a:id="@id/cpp_button_erase"
 			 a:src="@drawable/kb_delete"
 			 style="?cpp_control_image_button_style"
 			 a:onClick="eraseButtonClickHandler"/>
\ No newline at end of file
diff --git a/android-app/res/layout/calc_five_digit_button.xml b/android-app/res/layout/calc_five_digit_button.xml
index 4c59b34e..92fce03c 100644
--- a/android-app/res/layout/calc_five_digit_button.xml
+++ b/android-app/res/layout/calc_five_digit_button.xml
@@ -7,7 +7,7 @@
   -->
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/fiveDigitButton"
+													   a:id="@id/cpp_button_5"
 													   a:text="5"
 													   c:textUp="t"
 													   c:textLeft="E"
diff --git a/android-app/res/layout/calc_four_digit_button.xml b/android-app/res/layout/calc_four_digit_button.xml
index 06eabd24..8c40f283 100644
--- a/android-app/res/layout/calc_four_digit_button.xml
+++ b/android-app/res/layout/calc_four_digit_button.xml
@@ -7,7 +7,7 @@
   -->
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/fourDigitButton"
+													   a:id="@id/cpp_button_4"
 													   a:text="4"
 													   c:textUp="x"
 													   c:textLeft="D"
diff --git a/android-app/res/layout/calc_functions_button.xml b/android-app/res/layout/calc_functions_button.xml
index 53baae99..86d7b691 100644
--- a/android-app/res/layout/calc_functions_button.xml
+++ b/android-app/res/layout/calc_functions_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
     xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-    a:id="@+id/functions_button"
+    a:id="@id/cpp_button_functions"
     c:directionTextScale="0.5"
     c:textUp="+ƒ"
     a:text="ƒ(x)"
diff --git a/android-app/res/layout/calc_history_button.xml b/android-app/res/layout/calc_history_button.xml
index 517c216a..8a72e7be 100644
--- a/android-app/res/layout/calc_history_button.xml
+++ b/android-app/res/layout/calc_history_button.xml
@@ -7,7 +7,7 @@
   -->
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/historyButton"
+													   a:id="@id/cpp_button_history"
 													   a:text="@string/c_history_button"
 													   c:textUp="@string/c_undo"
 													   c:textDown="@string/c_redo"
diff --git a/android-app/res/layout/calc_left_button.xml b/android-app/res/layout/calc_left_button.xml
index 8116a5ac..e5ac610b 100644
--- a/android-app/res/layout/calc_left_button.xml
+++ b/android-app/res/layout/calc_left_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/leftButton"
+													   a:id="@id/cpp_button_left"
 													   c:textUp="◀◀"
 													   a:text="◀"
 													   c:directionTextScale="0.5"
diff --git a/android-app/res/layout/calc_multiplication_button.xml b/android-app/res/layout/calc_multiplication_button.xml
index 0ed0c46c..e9b500c0 100644
--- a/android-app/res/layout/calc_multiplication_button.xml
+++ b/android-app/res/layout/calc_multiplication_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/multiplicationButton"
+													   a:id="@id/cpp_button_multiplication"
 													   a:text="×"
 													   c:textUp="^"
 													   c:textDown="^2"
diff --git a/android-app/res/layout/calc_nine_digit_button.xml b/android-app/res/layout/calc_nine_digit_button.xml
index b920ea78..54b5abd3 100644
--- a/android-app/res/layout/calc_nine_digit_button.xml
+++ b/android-app/res/layout/calc_nine_digit_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/nineDigitButton" a:text="9"
+													   a:id="@id/cpp_button_9" a:text="9"
 													   c:textDown="e"
 													   c:textLeft="0x:"
 													   c:textUp="π"
diff --git a/android-app/res/layout/calc_one_digit_button.xml b/android-app/res/layout/calc_one_digit_button.xml
index 63c5fc05..af578994 100644
--- a/android-app/res/layout/calc_one_digit_button.xml
+++ b/android-app/res/layout/calc_one_digit_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/oneDigitButton"
+													   a:id="@id/cpp_button_1"
 													   a:text="1"
 													   c:textUp="sin"
 													   c:textLeft="A"
diff --git a/android-app/res/layout/calc_operators_button.xml b/android-app/res/layout/calc_operators_button.xml
index 425dcdb0..75309b22 100644
--- a/android-app/res/layout/calc_operators_button.xml
+++ b/android-app/res/layout/calc_operators_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
-													   a:id="@+id/functions_button"
+													   a:id="@id/cpp_button_operators"
 													   a:text="∂,…"
 													   a:onClick="operatorsButtonClickHandler"
 													   style="?cpp_control_button_style"/>
\ No newline at end of file
diff --git a/android-app/res/layout/calc_paste_button.xml b/android-app/res/layout/calc_paste_button.xml
index a6cd5e42..035740c6 100644
--- a/android-app/res/layout/calc_paste_button.xml
+++ b/android-app/res/layout/calc_paste_button.xml
@@ -7,7 +7,7 @@
   -->
 
 <ImageButton xmlns:a="http://schemas.android.com/apk/res/android"
-			 a:id="@+id/pasteButton"
+			 a:id="@id/cpp_button_paste"
 			 a:src="@drawable/kb_paste"
 			 style="?cpp_control_image_button_style"
 			 a:onClick="pasteButtonClickHandler"/>
\ No newline at end of file
diff --git a/android-app/res/layout/calc_plus_button.xml b/android-app/res/layout/calc_plus_button.xml
index 83e5531d..58b6a10b 100644
--- a/android-app/res/layout/calc_plus_button.xml
+++ b/android-app/res/layout/calc_plus_button.xml
@@ -7,7 +7,7 @@
   -->
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/plusButton"
+													   a:id="@id/cpp_button_plus"
 													   c:directionTextScale="0.5"
 													   c:textUp="°"
 													   c:textDown="E"
diff --git a/android-app/res/layout/calc_right_button.xml b/android-app/res/layout/calc_right_button.xml
index 35659042..6eea3dd9 100644
--- a/android-app/res/layout/calc_right_button.xml
+++ b/android-app/res/layout/calc_right_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/rightButton"
+													   a:id="@id/cpp_button_right"
 													   c:textUp="▶▶"
 													   a:text="▶"
 													   c:directionTextScale="0.5"
diff --git a/android-app/res/layout/calc_round_brackets_button.xml b/android-app/res/layout/calc_round_brackets_button.xml
index 719ceb09..7a7409cc 100644
--- a/android-app/res/layout/calc_round_brackets_button.xml
+++ b/android-app/res/layout/calc_round_brackets_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/roundBracketsButton"
+													   a:id="@id/cpp_button_round_brackets"
 													   c:textUp="("
 													   a:text="()"
 													   c:textDown=")"
diff --git a/android-app/res/layout/calc_seven_digit_button.xml b/android-app/res/layout/calc_seven_digit_button.xml
index 3518e3e6..4a61b9e6 100644
--- a/android-app/res/layout/calc_seven_digit_button.xml
+++ b/android-app/res/layout/calc_seven_digit_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/sevenDigitButton" a:text="7"
+													   a:id="@id/cpp_button_7" a:text="7"
 													   c:textUp="i"
 													   c:textLeft="0b:"
 													   c:textDown="!"
diff --git a/android-app/res/layout/calc_six_digit_button.xml b/android-app/res/layout/calc_six_digit_button.xml
index 47f619e1..0a4771d4 100644
--- a/android-app/res/layout/calc_six_digit_button.xml
+++ b/android-app/res/layout/calc_six_digit_button.xml
@@ -9,7 +9,7 @@
 <org.solovyev.android.calculator.view.AngleUnitsButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
 													   c:textUp="deg"
-													   a:id="@+id/sixDigitButton"
+													   a:id="@id/cpp_button_6"
 													   a:text="6"
 													   c:textLeft="F"
 													   c:textDown="rad"
diff --git a/android-app/res/layout/calc_subtraction_button.xml b/android-app/res/layout/calc_subtraction_button.xml
index 2ac9ea09..1beb5e6d 100644
--- a/android-app/res/layout/calc_subtraction_button.xml
+++ b/android-app/res/layout/calc_subtraction_button.xml
@@ -7,7 +7,7 @@
   -->
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/subtractionButton"
+													   a:id="@id/cpp_button_subtraction"
 													   c:textDown="∂,…"
 													   a:text="-"
 													   c:directionTextScale="0.5"
diff --git a/android-app/res/layout/calc_three_digit_button.xml b/android-app/res/layout/calc_three_digit_button.xml
index 63e7e588..4bdf9001 100644
--- a/android-app/res/layout/calc_three_digit_button.xml
+++ b/android-app/res/layout/calc_three_digit_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/threeDigitButton"
+													   a:id="@id/cpp_button_3"
 													   a:text="3"
 													   c:textUp="tan"
 													   c:textLeft="C"
diff --git a/android-app/res/layout/calc_two_digit_button.xml b/android-app/res/layout/calc_two_digit_button.xml
index d4456b65..d52b1065 100644
--- a/android-app/res/layout/calc_two_digit_button.xml
+++ b/android-app/res/layout/calc_two_digit_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/twoDigitButton"
+													   a:id="@id/cpp_button_2"
 													   a:text="2"
 													   c:textUp="cos"
 													   c:textLeft="B"
diff --git a/android-app/res/layout/calc_vars_button.xml b/android-app/res/layout/calc_vars_button.xml
index 85db3d2a..d7494c35 100644
--- a/android-app/res/layout/calc_vars_button.xml
+++ b/android-app/res/layout/calc_vars_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/vars_button"
+													   a:id="@id/cpp_button_vars"
 													   c:directionTextScale="0.5"
 													   c:textUp="+π"
 													   a:text="π,…"
diff --git a/android-app/res/layout/calc_zero_digit_button.xml b/android-app/res/layout/calc_zero_digit_button.xml
index dfa471e3..f377510d 100644
--- a/android-app/res/layout/calc_zero_digit_button.xml
+++ b/android-app/res/layout/calc_zero_digit_button.xml
@@ -8,7 +8,7 @@
 
 <org.solovyev.android.view.drag.DirectionDragButton xmlns:a="http://schemas.android.com/apk/res/android"
 													   xmlns:c="http://schemas.android.com/apk/res/org.solovyev.android.calculator"
-													   a:id="@+id/zeroDigitButton"
+													   a:id="@id/cpp_button_0"
 													   c:textUp="00"
 													   a:text="0"
 													   c:textDown="000"
diff --git a/android-app/src/main/java/org/solovyev/android/calculator/AbstractCalculatorHelper.java b/android-app/src/main/java/org/solovyev/android/calculator/AbstractCalculatorHelper.java
index a79fbbce..0ba59f44 100644
--- a/android-app/src/main/java/org/solovyev/android/calculator/AbstractCalculatorHelper.java
+++ b/android-app/src/main/java/org/solovyev/android/calculator/AbstractCalculatorHelper.java
@@ -87,12 +87,12 @@ public abstract class AbstractCalculatorHelper implements SharedPreferences.OnSh
         setOnDragListeners(root, dragPreferences, preferences);
 
         final OnDragListener historyOnDragListener = new OnDragListenerVibrator(newOnDragListener(new HistoryDragProcessor<CalculatorHistoryState>(getCalculator()), dragPreferences), vibrator, preferences);
-        final DragButton historyButton = getButton(root, R.id.historyButton);
+        final DragButton historyButton = getButton(root, R.id.cpp_button_history);
         if (historyButton != null) {
             historyButton.setOnDragListener(historyOnDragListener);
         }
 
-        final DragButton subtractionButton = getButton(root, R.id.subtractionButton);
+        final DragButton subtractionButton = getButton(root, R.id.cpp_button_subtraction);
         if (subtractionButton != null) {
             subtractionButton.setOnDragListener(new OnDragListenerVibrator(newOnDragListener(new SimpleOnDragListener.DragProcessor() {
                 @Override
@@ -108,64 +108,64 @@ public abstract class AbstractCalculatorHelper implements SharedPreferences.OnSh
 
         final OnDragListener toPositionOnDragListener = new OnDragListenerVibrator(new SimpleOnDragListener(new CursorDragProcessor(), dragPreferences), vibrator, preferences);
 
-        final DragButton rightButton = getButton(root, R.id.rightButton);
+        final DragButton rightButton = getButton(root, R.id.cpp_button_right);
         if (rightButton != null) {
             rightButton.setOnDragListener(toPositionOnDragListener);
         }
 
-        final DragButton leftButton = getButton(root, R.id.leftButton);
+        final DragButton leftButton = getButton(root, R.id.cpp_button_left);
         if (leftButton != null) {
             leftButton.setOnDragListener(toPositionOnDragListener);
         }
 
-        final DragButton equalsButton = getButton(root, R.id.equalsButton);
+        final DragButton equalsButton = getButton(root, R.id.cpp_button_equals);
         if (equalsButton != null) {
             equalsButton.setOnDragListener(new OnDragListenerVibrator(newOnDragListener(new EvalDragProcessor(), dragPreferences), vibrator, preferences));
         }
 
-        final AngleUnitsButton angleUnitsButton = (AngleUnitsButton) getButton(root, R.id.sixDigitButton);
+        final AngleUnitsButton angleUnitsButton = (AngleUnitsButton) getButton(root, R.id.cpp_button_6);
         if (angleUnitsButton != null) {
             angleUnitsButton.setOnDragListener(new OnDragListenerVibrator(newOnDragListener(new CalculatorButtons.AngleUnitsChanger(activity), dragPreferences), vibrator, preferences));
         }
 
-        final NumeralBasesButton clearButton = (NumeralBasesButton) getButton(root, R.id.clearButton);
+        final NumeralBasesButton clearButton = (NumeralBasesButton) getButton(root, R.id.cpp_button_clear);
         if (clearButton != null) {
             clearButton.setOnDragListener(new OnDragListenerVibrator(newOnDragListener(new CalculatorButtons.NumeralBasesChanger(activity), dragPreferences), vibrator, preferences));
         }
 
-        final DragButton varsButton = getButton(root, R.id.vars_button);
+        final DragButton varsButton = getButton(root, R.id.cpp_button_vars);
         if (varsButton != null) {
             varsButton.setOnDragListener(new OnDragListenerVibrator(newOnDragListener(new CalculatorButtons.VarsDragProcessor(activity), dragPreferences), vibrator, preferences));
         }
 
-        final DragButton functionsButton = getButton(root, R.id.functions_button);
+        final DragButton functionsButton = getButton(root, R.id.cpp_button_functions);
         if (functionsButton != null) {
             functionsButton.setOnDragListener(new OnDragListenerVibrator(newOnDragListener(new CalculatorButtons.FunctionsDragProcessor(activity), dragPreferences), vibrator, preferences));
         }
 
-        final DragButton roundBracketsButton = getButton(root, R.id.roundBracketsButton);
+        final DragButton roundBracketsButton = getButton(root, R.id.cpp_button_round_brackets);
         if (roundBracketsButton != null) {
             roundBracketsButton.setOnDragListener(new OnDragListenerVibrator(newOnDragListener(new CalculatorButtons.RoundBracketsDragProcessor(), dragPreferences), vibrator, preferences));
         }
 
         if (layout == CalculatorPreferences.Gui.Layout.simple) {
-            toggleButtonDirectionText(root, R.id.oneDigitButton, false, DragDirection.up, DragDirection.down);
-            toggleButtonDirectionText(root, R.id.twoDigitButton, false, DragDirection.up, DragDirection.down);
-            toggleButtonDirectionText(root, R.id.threeDigitButton, false, DragDirection.up, DragDirection.down);
+            toggleButtonDirectionText(root, R.id.cpp_button_1, false, DragDirection.up, DragDirection.down);
+            toggleButtonDirectionText(root, R.id.cpp_button_2, false, DragDirection.up, DragDirection.down);
+            toggleButtonDirectionText(root, R.id.cpp_button_3, false, DragDirection.up, DragDirection.down);
 
-            toggleButtonDirectionText(root, R.id.sixDigitButton, false, DragDirection.up, DragDirection.down);
-            toggleButtonDirectionText(root, R.id.sevenDigitButton, false, DragDirection.left, DragDirection.up, DragDirection.down);
-            toggleButtonDirectionText(root, R.id.eightDigitButton, false, DragDirection.left, DragDirection.up, DragDirection.down);
+            toggleButtonDirectionText(root, R.id.cpp_button_6, false, DragDirection.up, DragDirection.down);
+            toggleButtonDirectionText(root, R.id.cpp_button_7, false, DragDirection.left, DragDirection.up, DragDirection.down);
+            toggleButtonDirectionText(root, R.id.cpp_button_8, false, DragDirection.left, DragDirection.up, DragDirection.down);
 
-            toggleButtonDirectionText(root, R.id.clearButton, false, DragDirection.left, DragDirection.up, DragDirection.down);
+            toggleButtonDirectionText(root, R.id.cpp_button_clear, false, DragDirection.left, DragDirection.up, DragDirection.down);
 
-            toggleButtonDirectionText(root, R.id.fourDigitButton, false, DragDirection.down);
-            toggleButtonDirectionText(root, R.id.fiveDigitButton, false, DragDirection.down);
+            toggleButtonDirectionText(root, R.id.cpp_button_4, false, DragDirection.down);
+            toggleButtonDirectionText(root, R.id.cpp_button_5, false, DragDirection.down);
 
-            toggleButtonDirectionText(root, R.id.nineDigitButton, false, DragDirection.left);
+            toggleButtonDirectionText(root, R.id.cpp_button_9, false, DragDirection.left);
 
-            toggleButtonDirectionText(root, R.id.multiplicationButton, false, DragDirection.left);
-            toggleButtonDirectionText(root, R.id.plusButton, false, DragDirection.down, DragDirection.up);
+            toggleButtonDirectionText(root, R.id.cpp_button_multiplication, false, DragDirection.left);
+            toggleButtonDirectionText(root, R.id.cpp_button_plus, false, DragDirection.down, DragDirection.up);
         }
 
         CalculatorButtons.processButtons(theme, layout, root);
diff --git a/android-app/src/main/java/org/solovyev/android/calculator/AndroidNumeralBase.java b/android-app/src/main/java/org/solovyev/android/calculator/AndroidNumeralBase.java
index ecdc65aa..649493e8 100644
--- a/android-app/src/main/java/org/solovyev/android/calculator/AndroidNumeralBase.java
+++ b/android-app/src/main/java/org/solovyev/android/calculator/AndroidNumeralBase.java
@@ -22,7 +22,7 @@ public enum AndroidNumeralBase {
         @NotNull
         @Override
         public List<Integer> getButtonIds() {
-            return Arrays.asList(R.id.zeroDigitButton, R.id.oneDigitButton);
+            return Arrays.asList(R.id.cpp_button_0, R.id.cpp_button_1);
         }
     },
 
@@ -31,7 +31,7 @@ public enum AndroidNumeralBase {
         @Override
         public List<Integer> getButtonIds() {
             final List<Integer> result = new ArrayList<Integer>(bin.getButtonIds());
-            result.addAll(Arrays.asList(R.id.twoDigitButton, R.id.threeDigitButton, R.id.fourDigitButton, R.id.fiveDigitButton, R.id.sixDigitButton, R.id.sevenDigitButton));
+            result.addAll(Arrays.asList(R.id.cpp_button_2, R.id.cpp_button_3, R.id.cpp_button_4, R.id.cpp_button_5, R.id.cpp_button_6, R.id.cpp_button_7));
             return result;
         }
     },
@@ -41,7 +41,7 @@ public enum AndroidNumeralBase {
         @Override
         public List<Integer> getButtonIds() {
             final List<Integer> result = new ArrayList<Integer>(oct.getButtonIds());
-            result.addAll(Arrays.asList(R.id.eightDigitButton, R.id.nineDigitButton));
+            result.addAll(Arrays.asList(R.id.cpp_button_8, R.id.cpp_button_9));
             return result;
         }
     },
@@ -49,7 +49,7 @@ public enum AndroidNumeralBase {
     hex(CalculatorNumeralBase.hex) {
 
         @NotNull
-        private List<Integer> specialHexButtonIds = Arrays.asList(R.id.oneDigitButton, R.id.twoDigitButton, R.id.threeDigitButton, R.id.fourDigitButton, R.id.fiveDigitButton, R.id.sixDigitButton);
+        private List<Integer> specialHexButtonIds = Arrays.asList(R.id.cpp_button_1, R.id.cpp_button_2, R.id.cpp_button_3, R.id.cpp_button_4, R.id.cpp_button_5, R.id.cpp_button_6);
 
         @NotNull
         @Override