Feature: Add calculator app specification

Add calculator app specification

Resolves: N/a
See also: N/a

Projects/Calculator-App.md

@@ -0,0 +1,57 @@
+# Calculator
+
+**Tier:** 1-Beginner
+
+Calculators are not only one of the most useful tools available, but they are
+also a great way to understand UI and event processing in an application. In
+this problem you will create a calculator that supports basic arithmetic
+calculations on integers. 
+
+The styling is up to you so use your imagination and get creative! You might
+also find it worth your time to experiment with the calculator app on your
+mobile device to better understand basic functionality and edge cases.
+
+### Constraints
+
+- You may not use the `eval()` function to execute calculations
+
+## User Stories
+
+-   [ ] User can see a display showing the current number entered or the
+result of the last operation.
+-   [ ] User can see an entry pad containing buttons for the digits 0-9, 
+operations - '+', '-', '/', and '=', a 'C' button (for clear), and an 'AC'
+button (for clear all).
+-   [ ] User can enter numbers as sequences up to 8 digits long by clicking on
+digits in the entry pad. Entry of any digits more than 8 will be ignored.
+-   [ ] User can click on an operation button to display the result of that
+operation on:
+    * the result of the preceeding operation and the last number entered OR
+    * the last two numbers entered OR
+    * the last number entered
+-   [ ] User can click the 'C' button to clear the last number or the last
+operation. If the users last entry was an operation the display will be
+updated to the value that preceded it.
+-   [ ] User can click the 'AC' button to clear all internal work areas and
+to set the display to 0.
+-   [ ] User can see 'ERR' displayed if any operation would exceed the 
+8 digit maximum.
+
+## Bonus features
+
+-   [ ] User can click a '+/-' button to change the sign of the number that is
+currently displayed.
+-   [ ] User can see a decimal point ('.') button on the entry pad to that 
+allows floating point numbers up to 3 places to be entered and operations to
+be carried out to the maximum number of decimal places entered for any one
+number.
+
+## Useful links and resources
+
+- [Calculator (Wikipedia)](https://en.wikipedia.org/wiki/Calculator)
+- [MDN](https://developer.mozilla.org/en-US/)
+
+## Example projects
+
+- [Javascript Calculator](https://codepen.io/giana/pen/GJMBEv)
+- [React Calculator](https://codepen.io/mjijackson/pen/xOzyGX)

README.md

@@ -41,6 +41,7 @@ required to complete them.
 | ---------------------------------------------------------------------- | --------------------------------------------------------- | ---------- |
 | [Bin2Dec](./Projects/Bin2Dec-App.md)                                   | Binary-to-Decimal number converter                        | 1-Beginner |
 | [Border Radius Previewer](./Projects/Border-Radius-Previewer.md)       | Preview how CSS3 border-radius values affect an element   | 1-Beginner |
+| [🌟Calculator](./Projects/Calculator-App.md)                             | Calculator                                                | 1-Beginner |
 | [Christmas Lights](./Projects/Christmas-Lights-App.md)                 | Simulate a string of Christmas lights                     | 1-Beginner |
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