Math 203 Writing Assignment 4				Due Wednesday, Nov. 19

Choose one of the codes we discussed in class (listed below) and describe  
it.  You should talk about
- Who uses it
- What it looks like
	- length of ID number
	- number of check digits
	- if it uses numbers, letters or 0's and 1's
- What it's useful for (things like detecting transposition errors, error  
correcting, etc.)
- Demonstrate the checking process, including
	- how to determine check digits using the example below
	- how to check if a code is valid or not using your own examples,  
one that is valid and one that is not
	- if the code is error correcting, show how to correct your invalid 
example
	- if the code uses a bar code that we talked about, show a bar code  
that you can correct

Codes									 
Example (determine the check digit(s))
ISBN									987432187
U. S. Post Office money orders				3213578735
airlines, shipping, car rental					8973532
UPC 									
37544153751
ZIP + 4									68503-2782
4-digit binary code							0111