diff --git a/calculator.rb b/calculator.rb
new file mode 100644
index 0000000..6af1622
--- /dev/null
+++ b/calculator.rb
@@ -0,0 +1,195 @@
+# Yesenia Torres
+# calculator.rb 
+
+# METHODS ----------
+
+# Check validity of user input 
+def checkvalidint(num)
+    if num.to_i.to_s == num
+        return true
+    else return false
+    end
+end 
+
+def checkvalidfloat(num)
+    if num.to_f.to_s == num
+        return true
+    else return false
+    end
+end 
+
+# def convertinput(uncovertednum)
+#   this method should convert input to either float or int 
+# end 
+
+# Mathematical operations 
+def add(addnum1, addnum2)
+    return addnum1 + addnum2
+end
+
+def subtract(subnum1, subnum2)
+    return subnum1 - subnum2
+end 
+
+def multiply(multiplynum1, multiplynum2)
+    return multiplynum1 * multiplynum2
+end 
+
+def divide(divnum1, divnum2)
+    # Handle int / int = float case 
+    if  divnum1%divnum2 != 0
+        divnum1 = divnum1.to_f
+        divnum2 = divnum2.to_f
+    end 
+    return divnum1 / divnum2 
+end 
+
+# --------------------
+
+# Ask for operation 
+puts "Welcome to the Calculator Program! What math operation would you like me to perform? I can do the following: "
+puts "add (+), subtract (-), multiply (*), or divide (/)."
+operation = gets.chomp.to_s
+until ["add", "+", "subtract", "-", "multiply", "*", "divide", "/"].include?(operation)
+    puts "Hey buddy, I can't do that. Please only tell me to add (+), subtract (-), multiply (*), or divide(/)."
+    operation = gets.chomp
+end
+
+# Perform operation
+case (operation)
+
+    # Addition 
+    when "add", "+"
+        # Get a valid first number 
+        print "Give me a number to add to: "
+        num1 = gets.chomp
+        until (checkvalidint(num1) == true) || (checkvalidfloat(num1) == true)
+            print "Hey bro, that's not a valid number. Please enter a single integer or float: "
+            num1 = gets.chomp
+        end 
+        # Convert number to either int or float
+        if checkvalidint(num1) == true 
+            num1 = num1.to_i
+        elsif checkvalidfloat(num1) == true 
+            num1 = num1.to_f
+        end
+        # Get a valid second number 
+        print "How much would you like to add to that? "
+        num2 = gets.chomp
+        until (checkvalidint(num2) == true) || (checkvalidfloat(num2) == true)
+            print "Hey bro, that's not a valid number. Please enter a single integer or float: "
+            num2 = gets.chomp
+        end      
+        # Convert number to either int or float
+        if checkvalidint(num2) == true 
+            num2 = num2.to_i
+        elsif checkvalidfloat(num2) == true 
+            num2 = num2.to_f
+        end
+        # Print result 
+        puts "#{num1} + #{num2} = #{add(num1, num2)}, you're welcome!"
+    
+    # Subtraction
+    when "subtract", "-"
+
+        print "Give me a number to subtract from: "
+        num1 = gets.chomp
+        until (checkvalidint(num1) == true) || (checkvalidfloat(num1) == true)
+            print "Hey bro, that's not a valid number. Please enter a single integer or float: "
+            num1 = gets.chomp
+        end 
+
+        if checkvalidint(num1) == true 
+            num1 = num1.to_i
+        elsif checkvalidfloat(num1) == true 
+            num1 = num1.to_f
+        end
+
+        print "How much would you like to subtract from that? "
+        num2 = gets.chomp
+        until (checkvalidint(num2) == true) || (checkvalidfloat(num2) == true)
+            print "Hey bro, that's not a valid number. Please enter a single integer or float: "
+            num2 = gets.chomp
+        end      
+
+        if checkvalidint(num2) == true 
+            num2 = num2.to_i
+        elsif checkvalidfloat(num2) == true 
+            num2 = num2.to_f
+        end
+
+        puts "#{num1} - #{num2} = #{subtract(num1, num2)}, you're welcome!"
+    
+    # Multiplication 
+    when "multiply", "*"
+
+        print "Give me a number to multiply: "
+        num1 = gets.chomp
+        until (checkvalidint(num1) == true) || (checkvalidfloat(num1) == true)
+            print "Hey bro, that's not a valid number. Please enter a single integer or float: "
+            num1 = gets.chomp
+        end 
+
+        if checkvalidint(num1) == true 
+            num1 = num1.to_i
+        elsif checkvalidfloat(num1) == true 
+            num1 = num1.to_f
+        end
+
+        print "How much would you like to multiply that by? "
+        num2 = gets.chomp
+        until (checkvalidint(num2) == true) || (checkvalidfloat(num2) == true)
+            print "Hey bro, that's not a valid number. Please enter a single integer or float: "
+            num2 = gets.chomp
+        end      
+
+        if checkvalidint(num2) == true 
+            num2 = num2.to_i
+        elsif checkvalidfloat(num2) == true 
+            num2 = num2.to_f
+        end
+
+        puts "#{num1} * #{num2} = #{multiply(num1, num2)}, you're welcome!"
+    
+    # Division
+    when "divide", "/"
+
+        print "Give me a number to divide by: "
+        num1 = gets.chomp
+        until (checkvalidint(num1) == true) || (checkvalidfloat(num1) == true)
+            print "Hey bro, that's not a valid number. Please enter a single integer or float: "
+            num1 = gets.chomp
+        end 
+
+        if checkvalidint(num1) == true 
+            num1 = num1.to_i
+        elsif checkvalidfloat(num1) == true 
+            num1 = num1.to_f
+        end
+
+        print "How much would you like to divide that by? "
+        num2 = gets.chomp
+        until (checkvalidint(num2) == true) || (checkvalidfloat(num2) == true)
+            print "Hey bro, that's not a valid number. Please enter a single integer or float: "
+            num2 = gets.chomp
+        end      
+
+        if checkvalidint(num2) == true 
+            num2 = num2.to_i
+        elsif checkvalidfloat(num2) == true 
+            num2 = num2.to_f
+        end
+
+        puts "#{num1} / #{num2} = #{divide(num1, num2)}, you're welcome!"
+
+end 
+
+# Ways to improve: 
+# - handle numbers that begin with a ".", such as ".08"
+# - dry code: make any other methods to delete the repetitiveness? 
+
+# Missing Optional Enhancements : 
+# - Add support for computing exponents (2^4 = 2 * 2 * 2 * 2 = 16)
+# - Add support for the modulo operator (10 % 3 = 1).
+# - Add support for parentheticals, i.e. 10 / (5 + 5) = 1.
+# - Add support for handling all cases (uppercase, capitals) for the operations, so that ADD and add and Add (and other combinations) are handled in the same way