Hexadecimal, or Hex for short, is a numbering system based on counts of 16 – as opposed to decimal (the system most of us are most familiar with), which is based on counts of 10, or binary, which is based on counts of 2 (ones and zeros). The Hex characters range from 0 through F in the following order: 0, 1, 2, 3, 4, 5, 6, 7, 8, 8, A, B, C, D, E, F, where A represents our decimal “10,” B “11,” and so on.
The hexadecimal numbering system is commonly used as a handy way to describe computer data because it can represent every byte as a simple two digit value. For example, the binary numbers (or byte) 01101001 can be quickly seen in hex as 5D (in decimal this value would be 105). “Quickly” in the above context is a relative term; it does take a little practice to be able to “see” it. In order to be able to recognize when hex numbers are written they are usually accompanied by the dollar sign ($) or the letter “H” (or small “h”) immediately before or after. So the hex number above might be written $5D. MIDI is a data protocol that relies heavily on hex values for user input. Though these days most of the nuts and bolts of MIDI are well hidden from users, you will still see some hex values in many MIDI implementation charts that accompany most MIDI gear, and in some of the deeper MIDI sequencing programs.