Update README.md

Author: GoToLoop

README.md

@@ -1,2 +1,43 @@
 # Calculator
 Calculator example made w/ pure HTML + CSS + JS + JSDoc
+
+## Summary
+The code snippet is a JavaScript code that handles the functionality of
+a calculator on a webpage.
+
+It includes event handlers for keyboard input and button clicks,
+as well as functions to update the display and perform calculations.
+
+## Code Analysis
+### Inputs
+- Keyboard events triggered by pressing keys on the keyboard.
+- Button click events triggered by clicking on calculator buttons.
+___
+### Flow
+1. The code initializes the calculator by getting references to the calculator
+element, display element, and key buttons.
+2. It adds an event listener for keyboard input to the calculator element,
+which triggers the `btnKeyEvent` function.
+3. It adds event listeners for button clicks to each key button,
+which triggers the `btnCommonEvent` function.
+4. When a key is pressed on the keyboard, the `btnKeyEvent` function is called.
+5. The `btnKeyEvent` function handles specific key events, such as backspace
+and delete keys, and triggers click events on the corresponding button elements.
+6. When a button is clicked, the `btnCommonEvent` function is called.
+7. Function `btnCommonEvent` updates the display based on the clicked button,
+taking into account the current state of the calculator.
+8. The code snippet adds event listeners to specific buttons(zero, decimal,
+AC, CE, negate), which trigger their respective functions when clicked.
+9. The functions update the display and perform calculations based on the
+clicked button.
+___
+### Outputs
+- Updates the display element with the entered digits or operations.
+- Performs calculations based on the entered digits and operations.
+___
+
+https://GitHub.com/GoToLoop/Calculator
+
+https://GoToLoop.GitHub.io/Calculator
+
+https://bpa.st/VKXA