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/**

@mainpage 15-410 Project 1

@author Di Hu ([email protected])

- Link: https://www.cs.cmu.edu/~410/p1/proj1.html

The main task for P1 is to develop a game called Adventure

The Game part is already given, the rest of the task is to 
develop keyboard, timer and console drivers

1. Console
 - the console display is controlled by a region of memory through MMIO
 - the cursor is controlled by CRTC through IO ports

2. Timer
 - the timer is interrupt driven, communicated through IO ports
 - for this task, the timer is configured to fire an interrupt every 10 milliseconds

3. Keyboard
 - the keyboard is also interrupt driven through IO ports
 - on the keyboard interrupt, a one-byte scan code will be read from keyboard port
   and stored in a ring buffer defined in `keyboard.c`. 
   - the ring buffer has two indexes, the read index `rd_index` and write index `wr_index`
     when there is no data in the buffer, rd_index == wr_index
   - the indexes always increment. When they reach the end of the buffer, it is reset to 0

*/