Program 6

Polled I/O

Due: Monday, April 20

This is a variation of exercise 8.4 in Britton.

Write a program that reports how many instructions are executed between keyboard presses.

Outline of algorithm.

1.    Poll the keyboard until a key is pressed.
2.    Save the character pressed.
3.    Initialize a counter with the number of instructions executed after the key was pressed and now.
4.    Create a keyboard polling loop that increments a counter by the number of statements executed in the loop.
5.    Save the character pressed.
6.    Output the 2 characters and the value of the counter.

Note: While testing, remember the counter can hold a value no greater than 2³¹ - 1 (about 2 billion).  So, if you wait too long between presses, the counter will overflow and wrap around and give you strange answers.  That is ok and expected for now.

Extra credit: take care of the overflow/wraparound issue - be creative.