The little program below allows you to manipulate the 8 on/off "switches" (called bits) that make up a byte in typical computer communication. A computer really only senses current on or off at precisely timed intervals, but the 256 unique combinations of these 8 ons and offs can be interpreted differently depending on the application. The program shows some of the more common interpretations.
Humans don't deal with timed ons and offs very easily so the first interpretation we usually make is to binary math in which the ons and offs are converted to 0's and 1's. Reverse logic, common in electronics, makes the 1's represent current off and the 0's represent current on.
Although we could do calculations using binary math, it's easier for most of us to use decimal math. There are fewer digits to deal with, and most people feel more comfortable with this base-ten system.
Computer scientists and engineers who deal with the very large numbers that computers must use (like specific addresses among megabytes of RAM memory) often use hexadecimal numbers, a base-16 system in which the digits are: 0 1 2 3 4 5 6 7 8 9 A B C D E F. Each digit in hexadecimal can represent an entire nibble (4 bits), so an entire byte can be represented with only 2 digits.
The 256 combinations contained in a byte don't have to be interpreted as numbers; they can be used as codes to represent anything depending on the application being run. By far the most commonly used codes are those of ASCII (American Standard Code for Information Interchange). Through these codes, computers can communicate uppercase and lowercase letters, punctuation marks, numeric characters, simple graphic symbols, and invisible text formatting codes. ASCII codes are used throughout the world on all computer platforms. They make things like the Internet, email, and the World Wide Web possible.
For musicians, a common interpretation of bytes is as parts of a MIDI message. In the early eighties the International MIDI Association was formed to standardize the interpretation of the 256 codes into specific music related performance commands that could be used by sequencing applications and electronic musical instruments. These codes are detailed in the 31 page MIDI chapter handed out in class, but you can get a good overview of how they work here if you manipulate and study this little program. Of the two types of bytes in MIDI, Status and Data, the Status bytes (those represented by an MSB of 1) are the most interesting because they usually convey the basic commands like turning on notes and turning them off. Have fun!
After you play with this tutorial for a while, send me an email message that lets me know your impression. Does it help you understand this stuff any better? dsebald@lonestar.utsa.edu
Copyright 1998, Dave Sebald
Advanced Instructional Media
98-09-21