Doug Spence said: I have my office full of some of my favorite toys, and a large selection of classic computer documentation. It's a great stress reliever. Like I said, I stopped at this point, but you'll notice that once you read pass the two cycles that make up the sync bit, the rest of the cycles in that byte consist of one large cycle and one small cycle. If you compare the cycle lengths IN PAIRS then the different in small and large cycles becomes more pronounced and you can forget about the 15 samples definition.(One has to be smaller than the other) I didn't find the header format reference I mentioned, I do know that the header is read into the cassette buffer and I believe that make it about 191 or 192 bytes long. I also know that when the header is loaded into the cassette buffer in the C64: $033D - Low byte of start address $033E - High byte of start address $033F - Low byte of ending address $0340 - High byte of ending address $0341 - Start of the filename Looking at the printout I sent, it looks to me that the header starts with 9 to 1 countdown, then the header ID number. I (again) believe that 01 is the ID for a program header and 04 is the ID for a data file header. Then you have the start address (01 08 = $0801) and the ending address (23 08 = $0823). Followed by the filename. --Doug ==================================================== Doug Coward dcoward(a)pressstart.com (work) Sr. Software Eng. mranalog(a)home.com (home) Press Start Inc. http://www.pressstart.com Sunnyvale,CA ====================================================