Modern Computer Architecture and Organization

Modern Computer Architecture and Organization, by Jim Ledin. Published by Packt Publishing.


Chapter 1, Exercise 3

Modify the program of Exercise 2 to implement subtraction of 40-digit decimal values. Perform borrowing as required. Test with 0-0, 1-0, 1000000-1, and 0-1. What is the result for 0-1?

Answer

See the python file Ex__3_single_digit_subtractor.py for the single-digit subtractor code.

See the file Ex__3_test_single_digit_subtractor.py for the test code for the single-digit subtractor.

See the python file Ex__3_40_digit_subtractor.py for the 40-digit subtractor code.

See the file Ex__3_test_40_digit_subtractor.py for the test code for the 40-digit subtractor.

To execute the tests, assuming python is installed and is in your path, execute the commands python Ex__3_test_single_digit_subtractor.py and python Ex__3_test_40_digit_subtractor.py

This is the output of a test run of Ex__3_test_single_digit_subtractor.py:

C:\>python Ex__3_test_single_digit_subtractor.py
.......
----------------------------------------------------------------------
Ran 7 tests in 0.001s

OK

This is the output of a test run of Ex__3_test_40_digit_subtractor.py:

C:\>python Ex__3_test_40_digit_subtractor.py
....
----------------------------------------------------------------------
Ran 4 tests in 0.001s

OK
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