On Sun, 2024-12-22 at 22:26 -0600, jim stephens via cctalk wrote: > The fun story I have was from when I was playing one night and had > accidentally done a skip to channel, 12, which on our printer had no > stops, so it would jet paper out as fast as it could go.
The 1403 has a carriage control tape loop. It's about two inches wide, mounted at the top right. Each row corresponds to one print line. There are twelve columns along the tape, called "channels." Channel 1 is "top of form." That's the one the carriage skips to when you push the "carriage skip" button on the printer, or execute the "skip to channel 1" instruction in the 1401 (I don't know the 360 instruction). You can add punches in any other columns, for example you might want to skip to channel 3, four lines down the page, after printing a header. Maybe if you're printing statements or invoices you might want to skip to channel 5 to print the customer's address, and channel 7 to print the details etc. On the 1401, channel 12 is usually used to detect the bottom of the page. There's an instruction to ask if the printer is at column 12, called "branch if carriage overflow." But you can skip to any channel, so "skip to channel 12" would work. Indeed, that might be used to print footers, which have been what that program was trying to do. Why so many channels? It seems unlikely that any program would want to have twelve different carriage positions. But you could reserve channel 1 for top of page, and twelve for bottom of page, and then use the other odd ones for one program, and even ones for another program, so you wouldn't need to change carriage tapes.
