diff --git a/calculator.rb b/calculator.rb
index e7e20c6..8fc5989 100644
--- a/calculator.rb
+++ b/calculator.rb
@@ -6,6 +6,7 @@ class CalculatorEngine
 
   def initialize
     @memory = []  
+    @history = []
   end
 
 
@@ -18,19 +19,20 @@ def run
       
       if input
         input = input.chomp
+        @history.push(input)
 
         if input == 'q'
           done = true
         else
           # operators will work on the stack, numbers will be added to stack
           case input
-          when '0','1','2','3','4','5','6','7','8','9'    
-          	# ['0','1'].include?, %w(0 1).include?
-            @memory.push(input.to_f)
-            puts @memory.last
           when 'c'
             @memory = []
             puts "Memory Cleared"
+          when 'ca'
+            @memory = []
+            @history = []
+            puts "Memory and History Cleared"
           when 'm'
             puts "Memory:"
             position = 0
@@ -38,6 +40,24 @@ def run
               puts "\t#{position}: #{m}"
               position = position + 1
             end
+          when 'p'
+            puts "Paper Tape:"
+            position = 0
+            @history.each do |m|
+              puts "\t#{position}: #{m}"
+              position = position + 1
+            end
+          when 'pi'
+            @memory.push(3.14)
+            puts @memory.last
+          when 'sqrt'
+            if @memory.length >= 1
+              num = @memory.pop
+              @memory.push(Math.sqrt(num))
+              puts "= #{@memory.last}"
+            else
+              puts "Error: Not Enough Operands"
+            end
           when '+'
             if @memory.length >= 2
               op1 = @memory.pop
@@ -47,8 +67,44 @@ def run
             else
               puts "Error: Not Enough Operands"
             end
+          when '-'
+            if @memory.length >= 2
+              op1 = @memory.pop
+              op2 = @memory.pop
+              @memory.push(op1 - op2)
+              puts "= #{@memory.last}"
+            else
+              puts "Error: Not Enough Operands"
+            end
+          when '*'
+            if @memory.length >= 2
+              op1 = @memory.pop
+              op2 = @memory.pop
+              @memory.push(op1 * op2)
+              puts "= #{@memory.last}"
+            else
+              puts "Error: Not Enough Operands"
+            end
+          when '/'
+            if @memory.length >= 2
+              op1 = @memory.pop
+              op2 = @memory.pop
+              @memory.push(op1 / op2)
+              puts "= #{@memory.last}"
+            else
+              puts "Error: Not Enough Operands"
+            end
+          when '0','1','2','3','4','5','6','7','8','9'    
+            # ['0','1'].include?, %w(0 1).include?
+            @memory.push(input.to_f)
+            puts @memory.last
           else
-            puts "Error: Unsupported Operator: #{input}" unless input.empty?
+            if input =~ /^\d+\.\d*$/
+              @memory.push(input.to_f)
+              puts @memory.last
+            else
+              puts "Error: Unsupported Operator: #{input}" unless input.empty?
+            end
           end
 
         end