I was fairly young when I first heard about “rolling the odometer” – this was decades ago, before cars became so computerized. Back then, odometers were mechanical devices (instead of LED displays), and generally had only five digits (instead of six). When the numbers reached 99,999 many drivers would like to watch their odometer roll over back to 00,000 again. I can only assume that they were being prudent and deliberately drove on a quiet side street during this changeover rather than on a busy highway, or wherever they happened to be at that moment.
Since car odometers now have LED digits, the magic is gone – an LED display incrementing from one number to the next is pretty much the same experience all the time. Today’s car odometers also have six digits, so the chances of driving the same car for one million miles. and rolling the odometer, are remote.
Earlier this year, I had my own odometer rollover experience, even though it’s also a six-digit LED model. I wasn’t even close to having one million miles on my car, but this past July it passed the 65,000 km mark. While this may not mean anything to you, it was a significant milestone (or kilometrestone) to a computer geek like myself – the ominous 65,536 km reading was just around the proverbial corner.
For you non-geeks, let me explain why this (and other numbers) are so significant. A generation ago, cars used to be almost completely mechanical; now they are becoming increasingly computerized. Many of their systems are controlled by microprocessors, which use binary numbers.
Back in the 1980s, if you owned and programmed a VIC-20, Commodore-64, Atari-400, Atari-800, Apple II, then you are familiar with an 8-bit microprocessor. These early personal computers used the 6502 chip, which had an 8-bit processor and a 16-bit address bus. The 8-bit processor meant that each memory location could store a maximum value of 2^8 (2 to the 8th power). This value is 256, but since computers begin their numbers at zero instead of one, the range is actually 0-255. If you tried to enter any number higher than 255 into any memory location, then you would receive an error message. In binary, 255 is “11111111”; you can’t input a higher value because each of the eight bits already contains the highest binary value: 1. The memory addressing in these early personal computers was 16-bit, which means that the highest memory location was 2^16 (2 to the 16th power). This number is 65,536 (minus one, since computer numbering begins at zero). If you tried to examine any memory location higher than 65,535, you would also receive an error message, since those locations don’t exist. In binary, 65,535 is represented as “11111111 11111111”; for the same reason, this is the highest accessible memory location in a (16-bit) computer.
My car’s odometer passed the 256 km mark fairly soon after I bought it, so I knew that it wasn’t an 8-bit machine. During the summer of 2011, as the odometer passed the 65,000 km mark, the next test was imminent – what if my car used a 16-bit computer system, meaning that the highest value that could be addressed by this computer was 2^16-1, or 65,535? What would happen when the odometer reached this number? Would there be an “illegal quantity error” or some sort of overflow error? Would the on-board computer crash? Would the controls freeze? Would my dashboard display its own version of the dreaded Windows BSOD (Blue Screen Of Death)? Would I have to turn off my car and then start it again? As the numerical display kept incrementing I was starting to get a little worried…
Before you start mocking both my geekiness and my technological hypochondria, let me say one thing: the world is supposed to end in 2012. Yes, the media is gearing up for yet another apocalypse, and this one is based on the same principle. The Mayan calendar measures time only up to the end of this year, and as I’m sure you’ve heard by now, some people believe this means that the world is going to end when their calendar stops measuring time, on December 21, 2012. I find it astounding that in the 21st century, there are still people among us who believe that if they can’t measure something, then the fault lies not with the limitations of their measuring device, but with whatever they happen to be measuring with it (even time). If their measuring device can’t quantify something, then it cannot exist. Using the same logic, if I gave these people a yardstick and told them to extend it straight out in front of their bodies, I could argue that the edge of the universe is only three feet (plus an arm’s length) in front of them. Therefore, anything they might see beyond the yardstick is clearly an illusion.
What’s actually happening is that December 21, 2012 is last date that can be represented on the Mayan calendar. According to their system of time measurement, the base unit is called a K’in, and is equal to one day. There are 20 K’in in a Winal (20 days), 18 Winal in a Tun (360 days), 20 Tun in a K’atun (19.7 years), 20 K’atun in a B’ak’tun (394.3 years) and 12 B’ak’tun represented in the entire calendar (4731.6 years). This coming December 21 (2012), the Mayan calendar will read as follows: 12 B’ak’tun, 19 K’atun, 19 Tun, 17 Winal, and 19 K’in. In the same way that the computer’s bits were all set to “1”, the Mayan calendar is now completely filled up, and like an odometer changing from 99,999 to 00,000, it will simply “roll over” and the 13th B’ak’tun will begin on December 22 (displayed, one would presume, on the Mayan equivalent of an IPv6 calendar).
As a side note, if you are one of those people who genuinely believes that the world is going to end this year, then come December, you won’t have any further need for your worldly possessions – computer equipment, iPhones (4S only), DVD collections (BluRay only), RRSPs, flat-screen LCD or LED televisions (1080p, 55″ and up), vintage European sports cars, single malt Scotch (not blended) – so feel free to donate everything to me. Depending on the quality of the Scotch, I may gaze skyward and make a toast in your honour.
Finally, since my car’s odometer hit the 65,000 km mark last summer, I’m sure that you’ve already guessed what happened… sometime in July, the numbers incremented uneventfully from 65,535 to 65,536. I was driving on the highway at the time and I didn’t actually check it until 10-15 kilometres later. Everything was (and still is) working properly, so my car is obviously not using a 16-bit computer. However, I mustn’t allow myself to become complacent – my vehicle could be saddled with a menial 32-bit microprocessor, and that means I’ll become apprehensive once again as my odometer approaches 2^32… or 4,294,967,296 km…