ADVENT #24 — 9-track tape

’twas the night before Christmas, when all through the house / Not an input was pending, not even a mouse; / The tapes were all hung by the the ….

Neither you nor I want me to continue down the path of novelty poetry, especially through all that new-fallen snow. I can’t be sure that the famous 1823 poem “A Visit from St. Nicholas” inspired Babbage’s 1837-era Analytical Engine but I have my suspicions. The poem’s influence on later computing systems is indisputable. So much computing and nowhere is the influence plainer than here: “When what to my wondering eyes did appear, But a miniature sleigh and eight tiny rein-deer, With a little old driver so lively and quick, I knew in a moment he must be St. Nick.” A flying head for eight bits? With a quick driver? By a Saint? A coincidence that we still call SCSI tape devices /dev/st*? Hardly.

A lot has changed in the two hundred and one years since that poem revolutionized computing and marked out territory for the 8-bit byte over the 6-bit form that lesser systems would have us use. One big change is that we no longer name the bits in a bytes after Santa’s reindeer, instead using the humdrum system of least-significant bit to most-significant. Back when we used the reindeer system, I used to sometimes confuse Comet and Cupid bit positions.

I wonder if you recall Rudolph, the most famous reindeer of all. Rudolph, reindeer number nine, represents the parity bit in the system. This makes perfect sense when you recall that his red nose lights up only about half the time.

It’s Rudolph’s contribution that really put the then-new IBM 360 mainframe and its associated 9-track tape system over the top in 1964. The famous stop-motion Rudolph TV special was released the same year. What else do IBM mainframes and mid-century stop-motion TV specials have in common? The single step. Operators at the console of a System 360 mainframe could single step the machine with a handy knob. I suppose you could also individually pose each card in the card reader before steps but this is a tedious way to debug and/or make a children’s TV special.

I was only a user of an IBM mainframe for a semester of numerical analysis in FORTRAN and that was quite enough for me. My experience with 9-track tape predates that. My first job that was not a cash-under-the-table food service thing was as an evening lab aide in a community college computer lab. One of the end-of-the-night duties was backing up the department’s HP 3000 Series 33 minicomputer. High school student me had been trained on the commands and the manual tape loading required. I knew how to thread the tape from the spool, through the drive, and onto the take-up spool. I had not been trained for what happened on my first night, which is that the take-up spool flew off the spindle and sent tape flying everywhere. I somehow wasn’t fired and I lived to run many successful backups on the system.

The experience soured me on 9-track tape and on HP’s miserable MPE operating system, but not on computing, tape, or removable media generally.

One of the most remarkable things about the 9-track tape was that the seal clamp had an integrated hook that let the tapes hang like bats on special tape rack furniture. We’ve covered a lot of media in the last month but entirely skipped the associated ecosystem of media-specific furniture. Media furniture ran from room-sized tape racks to desktop floppy disk organizers and smart little smart card wallets for removable digital camera media. I think about it every time I shop for an attractive storage solution for my own LP records.

No Alice hacking today — it’s Christmas Eve. May there be some removable media under the tree for you all.