diff --git a/calculator.rb b/calculator.rb
new file mode 100644
index 0000000..9a47f6a
--- /dev/null
+++ b/calculator.rb
@@ -0,0 +1,74 @@
+# Baseline
+# The program should ask the user for an operation (string or numeric symbol) and two numbers.
+
+# Primary Requirements
+# The program should use the input operation and two numbers to provide the result of applying the operation to the two numbers.
+# The program should have support for these four operations: addition, subtraction, multiplication, and division.
+# The program should accept both the name (`add`) and the symbol (`+`) for each possible operation.
+
+# define methods for adding, subtracting, multiplying, and dividing
+def addition(x, y)
+  x + y
+end
+
+def subtraction(x, y)
+  x - y
+end
+
+def multiplication(x, y)
+  x * y
+end
+
+def division(x, y)
+  x / y
+end
+
+# Welcome user and test for/handle erroneous input 
+
+puts "Welcome to Calculator!"
+puts "I'm going to ask you for two numbers, and an operator. What is your first number?: "
+num_1 = gets.chomp
+
+until num_1 =~ /\d/
+  puts "That's not a number, try again: "
+  num_1 = gets.chomp
+end
+
+puts "Great! What is your second number? (Must be greater than zero)"
+num_2 = gets.chomp
+
+until (num_2 =~ /\d/)
+  puts "That's not a number. Try again: "
+  num_2 = gets.chomp
+end
+
+if num_2.to_i <= 0
+  puts "Number must be greater than zero, try again: "
+  num_2 = gets.chomp
+end
+
+puts "Awesome. Now, what would you like to do to these numbers? You can type add (+), subtract (-), multiply (*), or divide (/)"
+operator = gets.chomp
+
+# Case statement that tests the value of the operator variable
+# The program also needs to handle erroneous operators.
+
+loop do
+  case operator
+  when "add", "+"
+    puts addition(num_1.to_f, num_2.to_f)
+    break
+  when "subtract", "-"
+    puts subtraction(num_1.to_f, num_2.to_f)
+    break
+  when "multiply", "*"
+    puts multiplication(num_1.to_f, num_2.to_f)
+    break
+  when "divide", "/"
+    puts division(num_1.to_f, num_2.to_f)
+    break
+  else
+    puts "Invalid input, try again: "
+    operator = gets.chomp
+  end
+end