Fun with TI-74s - Hamming codes

[JGardner]

Error-correcting codes are a fascinating subject, despite the occasional tendency

for eyes to cross while enjoying their mathematical derivations...

Richard Hamming also later gave us two classics, "Numerical Methods For Scientists

And Engineers", and "Digital Filters" - By all means; don't deprive yourself...

But anyway -

Hamming codes are something I've been aware of for many years, without an

excuse to indulge; this changed recently - As a first step to getting up to speed I

thought I'd try a TI-74 BASIC demo implementation.

Easier said than done, it turned out, but it seems to work. (If you find differently,

I'd like to hear of it...)


errors noted -

1) terminology; code is Hamming 12,8, not 8,4 ...

b) pseudo-random byte (0-255) generator should be: INT(RND*INT(256+.5)+1)-1

 

[JGardner]

A Hamming 8,4 example...

Enter a nybble at the prompt. Pgm displays the entry on binary format, then

expands the nybble to Hamming format and displays it. Press [ENTER] .

The Hamming formatted byte is then displayed - The blinking cursor prompts

for a 1 or 2 bit change.* The algorithm processes the entry appropriately and

displays the result.


* The result of changing more than 2 bits is an undetected error.