Although most of you figured it out, I received some questions regarding last week’s crossword puzzle, specifically 1-Down, “Slang for ‘Trace On.'”

I suppose I could have reworded it slightly. Perhaps “In the days of BASIC, computer-speak for ‘Trace On'” would have been better, however you’ll notice that the sub-title of the crossword was “e-commerce, a return to networking, and one movie.” To me, that was a giveaway. Did you wonder what the movie was? It was the slang term for “Trace On,” or TRON.

You may remember I made a post recently about an on-line BASIC interpreter, BASIC being an early computer-programming language, and that is the kind of BASIC we are talking about – the kind where each line is preceded by a line number. Here is an example of what it looks like:

Believe it or not, this is a relatively simple BASIC program, but they could be very complex. You can see that each line is preceded by a line number, and that made it easy to follow what was happening, for two reasons. First, if the program crashed it would tell you at which number the crash happened. Second, you can trace the running of the program using the TRON command, and when the program is run it won’t just add two numbers or compute sales tax or whatever it’s supposed to do, but as each line executes that line number will appear on the screen. The effect is that the second you type ‘run’ your screen fills up with a cascade of numbers, but it really does help diagnose how specifically a program executes and where problems, lockups, freezes, or crashes occur.

You might be wondering if there is a complimentary TROFF command. It makes sense there would be, right? How else would you stop the TRON command? In fact, there *is* a TROFF command that stops the trace. If may offer opinion, I’m of the belief that TROFF should have been the title of the recent, abysmal sequel to the original, glorious TRON movie. To be fair, the original TRON was released when technology was, at least to the general public, still undiscovered country. But now that everyone has a smartphone it’s difficult for a movie taking place inside a machine to have the same wonder and mystery.

I have recorded a very brief (2:42) video giving an example of how TRON and TROFF work in practice, using a very short three-line program and the MMBasic interpreter. I explain the program, run it, then run it with TRON so you can see the difference and how the executing line numbers are traced. The I turn tracing off, and the program returns to normal.

Tron as a command was widely used, sometimes built in to the PC itself. To show you visceral evidence, here is a picture of my IBM 5140 PC, released to the public all the way back in 1986, four years after TRON the movie was released.

IBM 5140 PC, 1986

It’s difficult to see in the above photo, but there is a taskbar of sorts along the bottom of the screen offering various commands. You can see it a little better in the image below:

Notice number 7 and 8 in the command bar. Why, it’s none other than TRON and TROFF, the answer to 1-Down and an actual pair of commands that were used relatively frequently for years in the 80’s and early 90s. It has been superseded by other commands and by the abilities of current Integrated Development Environments that can provide very detailed information about why your program isn’t working, but the term itself is well steeped in the annals of technology.

Here’s your close-up!