diff --git a/apps/calculation/calculation.cpp b/apps/calculation/calculation.cpp
index c18ff004e..9078ac7c8 100644
--- a/apps/calculation/calculation.cpp
+++ b/apps/calculation/calculation.cpp
@@ -4,13 +4,28 @@
 namespace Calculation {
 
 Calculation::Calculation() :
-  m_text(""),
   m_expression(nullptr),
   m_layout(nullptr),
-  m_evaluation(Float(0.0f))
+  m_evaluation(0.0f)
 {
 }
 
+Calculation & Calculation::operator= (const Calculation & other) {
+  strlcpy(m_text, other.m_text, sizeof(m_text));
+  if (m_expression != nullptr) {
+    delete m_expression;
+  }
+  m_expression = Expression::parse(m_text);
+  if (m_layout != nullptr) {
+    delete m_layout;
+  }
+  if (m_expression) {
+    m_layout = m_expression->createLayout();
+  }
+  m_evaluation = other.m_evaluation;
+  return *this;
+}
+
 void Calculation::setContent(const char * c, Context * context) {
   strlcpy(m_text, c, sizeof(m_text));
   if (m_expression != nullptr) {
@@ -45,8 +60,15 @@ ExpressionLayout * Calculation::layout() {
   return m_layout;
 }
 
-Float * Calculation::evaluation() {
-  return &m_evaluation;
+float Calculation::evaluation() {
+  return m_evaluation;
+}
+
+bool Calculation::isEmpty() {
+  if (m_expression == nullptr) {
+    return true;
+  }
+  return false;
 }
 
 }
diff --git a/apps/calculation/calculation.h b/apps/calculation/calculation.h
index f7baa3eca..63be1a615 100644
--- a/apps/calculation/calculation.h
+++ b/apps/calculation/calculation.h
@@ -8,18 +8,20 @@ namespace Calculation {
 class Calculation {
 public:
   Calculation();
-  ~Calculation(); // Delete expression and layout, if needed
+    ~Calculation(); // Delete expression and layout, if needed
+  Calculation & operator= (const Calculation & other);
   const char * text();
   Expression * expression();
   ExpressionLayout * layout();
-  Float * evaluation();
+  float evaluation();
   void setContent(const char * c, Context * context);
+  bool isEmpty();
 private:
   constexpr static int k_bodyLength = 255;
   char m_text[k_bodyLength];
   Expression * m_expression;
   ExpressionLayout * m_layout;
-  Float m_evaluation;
+  float m_evaluation;
 };
 
 }
diff --git a/apps/calculation/calculation_store.cpp b/apps/calculation/calculation_store.cpp
index 143e7a047..b93b0e203 100644
--- a/apps/calculation/calculation_store.cpp
+++ b/apps/calculation/calculation_store.cpp
@@ -4,46 +4,47 @@
 namespace Calculation {
 
 CalculationStore::CalculationStore() :
-  m_numberOfCalculations(0),
-  m_startIndex(0)
+  m_start(m_calculations)
 {
 }
 
-Calculation * CalculationStore::calculationAtIndex(int i) {
-  assert(i>=0 && i<m_numberOfCalculations);
-  int index = (m_startIndex+i) - m_numberOfCalculations*(int)((m_startIndex+i)/m_numberOfCalculations);
-  return &m_calculations[index];
-}
-
-Calculation * CalculationStore::addEmptyCalculation() {
-  //TODO: change the model
-  if (m_numberOfCalculations >= k_maxNumberOfCalculations) {
-    for (int k = 0; k < k_maxNumberOfCalculations; k++) {
-      m_calculations[k] = m_calculations[k+1];
-    }
-    m_numberOfCalculations--;
+Calculation * CalculationStore::push(Calculation * c) {
+  Calculation * result = m_start;
+  *m_start++ = *c;
+  if (m_start >= m_calculations + k_maxNumberOfCalculations) {
+    m_start = m_calculations;
   }
-  Calculation addedCalculation = Calculation();
-  m_calculations[m_numberOfCalculations] = addedCalculation;
-  Calculation * result = &m_calculations[m_numberOfCalculations];
-  m_numberOfCalculations++;
   return result;
 }
 
-void CalculationStore::removeCalculation(Calculation * c) {
-  int i = 0;
-  while (&m_calculations[i] != c && i < m_numberOfCalculations) {
-    i++;
-  }
-  assert(i>=0 && i<m_numberOfCalculations);
-  m_numberOfCalculations--;
-  for (int j = i; j<m_numberOfCalculations; j++) {
-    m_calculations[j] = m_calculations[j+1];
+Calculation * CalculationStore::calculationAtIndex(int i) {
+  int j = 0;
+  Calculation * currentCalc = m_start;
+  while (j<=i) {
+    if (currentCalc >= m_calculations + k_maxNumberOfCalculations) {
+      currentCalc = m_calculations;
+    }
+    if (!currentCalc->isEmpty()) {
+      j++;
+    }
+    currentCalc++;
   }
+  return currentCalc-1;
 }
 
 int CalculationStore::numberOfCalculations() {
-  return m_numberOfCalculations;
+  Calculation * currentCalc= m_calculations;
+  int numberOfCalculations = 0;
+  while (currentCalc < m_calculations + k_maxNumberOfCalculations) {
+    if (!currentCalc++->isEmpty()) {
+      numberOfCalculations++;
+    }
+  }
+  return numberOfCalculations;
+}
+
+void CalculationStore::deleteCalculationAtIndex(int i) {
+  *calculationAtIndex(i) = Calculation();
 }
 
 }
diff --git a/apps/calculation/calculation_store.h b/apps/calculation/calculation_store.h
index 3f0dcd1c3..c15e5a1ff 100644
--- a/apps/calculation/calculation_store.h
+++ b/apps/calculation/calculation_store.h
@@ -9,13 +9,12 @@ class CalculationStore {
 public:
   CalculationStore();
   Calculation * calculationAtIndex(int i);
-  Calculation * addEmptyCalculation();
-  void removeCalculation(Calculation * c);
+  Calculation * push(Calculation * c);
+  void deleteCalculationAtIndex(int i);
   int numberOfCalculations();
 private:
-  static constexpr int k_maxNumberOfCalculations = 10;
-  int m_numberOfCalculations;
-  int m_startIndex;
+  static constexpr int k_maxNumberOfCalculations = 5;
+  Calculation * m_start;
   Calculation m_calculations[k_maxNumberOfCalculations];
 };
 
diff --git a/apps/calculation/edit_expression_controller.cpp b/apps/calculation/edit_expression_controller.cpp
index 59987ff45..16885213f 100644
--- a/apps/calculation/edit_expression_controller.cpp
+++ b/apps/calculation/edit_expression_controller.cpp
@@ -68,9 +68,10 @@ bool EditExpressionController::handleEvent(Ion::Events::Event event) {
   switch (event) {
     case Ion::Events::Event::ENTER:
     {
-      Calculation * calculation = m_calculationStore->addEmptyCalculation();
+      Calculation calculation = Calculation();
       App * calculationApp = (App *)app();
-      calculation->setContent(textBody(), calculationApp->globalContext());
+      calculation.setContent(textBody(), calculationApp->globalContext());
+      m_calculationStore->push(&calculation);
       m_historyController->reload();
       m_contentView.textField()->setTextBuffer("");
       return true;
diff --git a/apps/calculation/history_view_cell.cpp b/apps/calculation/history_view_cell.cpp
index fa27eaaf1..94e4c57f7 100644
--- a/apps/calculation/history_view_cell.cpp
+++ b/apps/calculation/history_view_cell.cpp
@@ -34,7 +34,7 @@ void HistoryViewCell::layoutSubviews() {
 void HistoryViewCell::setCalculation(Calculation * calculation) {
   m_calculation = calculation;
   char buffer[7];
-  m_calculation->evaluation()->convertFloatToText(buffer, 14, 7);
+  Float(m_calculation->evaluation()).convertFloatToText(buffer, 14, 7);
   m_result.setText(buffer);
 }