Binary Digits

Mon, 02 Sep 2024 01:46:04 GMT

Say you were a young college student taking a programming class, and your aging computer science professor’s first assignment was for each student to write a program to print out their name and telephone number.

That wouldn’t be the least bit sus, now would it?

Apparently, back in 1984 it wasn’t! Lemme tell you a story…

I was recently bedridden with both a back injury and my first case of Covid. And having already purged many of my old books, I really had to stretch (metaphorically, of course) to find something to entertain myself with.

One book that followed me through my migrations – from Maine to (five different locations in) Massachusetts, then Pittsburgh, and finally Texas – was a college textbook that was highly cherished by most of the CS majors I knew back then: George Struble’s “Assembler Language Programming for the IBM System/370 Family”.

Yes, I was so bored that I started re-reading a 40 year old textbook on one of the driest topics in all of computer science, for a computer that no longer exists!

Chapter 1 is a snoozer (not unlike the rest of the book). It’s all about how mainframe computers used combinations of ones and zeroes to encode numbers and characters. Like any textbook, the end of Chapter 1 had a dozen exercises for the student to solve, to promote active learning and demonstrate a practical understanding of what’s been taught.

Here’s the text of Problem 1.3: (emphasis mine)

Each byte of storage in the IBM System/370 contains eight bits of information and one parity bit. The parity bit is redundant; it is used only to guarantee that information bits are not lost. The parity bit is set to 1 or 0 so as to make the sum of 1’s represented in the nine bits an odd number. For example, the character / is represented in eight bits (in EBCDIC) by 01100001. The parity bit to go with this character will be 0, because there are three 1’s among the information-carrying bits. The character Q is represented by 11011000, and the parity bit is set to 1, so there will be five 1-bits among the nine. These representations with parity bit (we call this “odd parity”) are also used in magnetic tape and disk storage associated with the IBM System/370. Using the character representation table of Appendix A, code your name and telephone number in eight-bit EBCDIC representations, and add the correct parity bit to each character.

That’s right: on just the third exercise in the entire book, Struble is asking the student to provide their personal contact info, presumably to their instructor. I can only imagine the repercussions if a professor presented this exercise to his or her class today.

To be fair, when Struble’s book came out (in 1969, then revised in 1974 and again in 1984) such an assignment simply wouldn’t have set off the red flags it does today. The author and his editors probably felt safe in the assumption that women wouldn’t be taking hard-core mainframe assembler classes. And for the odd exception, what harm could possibly come from a young coed revealing her phone number to an upstanding member of the academic community?

What harm, indeed.

I’m not one to condemn past generations for not living up to more modern social norms, but still… Today that exercise just screams of inappropriateness and invasion of privacy. For me, reading that was a head-scratching moment of astonishment from an unexpected source, a true blast from my past.

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Metrics of Success

Fri, 08 Apr 2022 20:01:39 GMT

Say an alien civilization conquered Earth and forced us to use their measurements, outlawing familiar units like the mile, degree, pound, and gallon. Imagine how disruptive that would be!

Akshually, not very disruptive at all, based on my experience. This year I decided it was finally time to drop those long-outdated “imperial” units and resolved to go full-time 100% metric only.

Why? Well, as an international sport, cycling and bicycles are primarily metric in nature. In any field where measurements matter, metric is used… even in the United States. By law, metric became the preferred measurement system in the U.S. back in 1975, and we’ve had sixty years to get used to the idea of using modern, standardized, universally-recognized units. Our quaint idiosyncratic measurements have become less and less defensible with each passing year. This is just my way of saying “Really, don’t you retrogrades think it’s about time?”

I am reminded of a bike ride I did up Gun Hill in Barbados back in June of 2000, when I was a novice first getting back into riding a bicycle. When I rode that hill under the hot tropical midday sun, it seemed way steeper and harder than the 210-foot ascent that my map indicated. Then I realized that Michelin travel map wasn’t demarcated in feet, but in meters. At 700 feet the hill was actually more than three times steeper than I had bargained for! And whose fault was that? It certainly wasn’t Michelin’s… And my legs have never let me forget that lesson.

It could be worse, tho. Back in 1999, a $125 million Mars Climate Orbiter crashed during its insertion burn because no one thought to convert numbers from Lockheed Martin’s imperial units into JPL’s metric ones. Awkward!

Compared to those experiences, adapting to metric units hasn’t taken much adjustment at all.

What did I need to change? Well, let’s look at things like a cyclist. What matters to a cyclist? Distances, speed, inclines, air temperature, tire pressures, and the weight of his equipment and body.

Distance isn’t that hard. A meter is just a slightly longer yard, and a kilometer is a somewhat shorter mile. And many rides are already demarcated in kilometers: a metric century (100 km = 62 miles), a 200k (124 miles), and so on. And like most men I stand a little shy of 2 meters in height.

Speed is simply distance divided by time (whose units haven’t changed), so you wind up with km/h as a rough analogue for mph. A familiar 15 mph average speed would equate to about 24 km/h; and a 10 mph headwind would be 16 km/h.

Similarly, inclines are just vertical distance divided by horizontal distance. So if you’re used to thinking in terms of feet per mile, you need to divide by 5¼ to recalibrate to meters per kilometer. And unlike feet per mile, you can simply divide m/km by 100 to get percent slope! That’s handy!

Air temperature really isn’t hard, either. I break it down into ten-degree chunks. Obviously, 0C equals 32F. From there, 10C = 50F, 20C = 68F, and 30C = 86F. There’s nothing complex about that.

Like the other metric units, weight is another one where routine use creates familiarity. My weight usually runs in the 76 to 78 kg range.

And air pressure, too. I run my bike tires at 550 kPa, and the car’s at 220 kPa. Those you would just have to remember, if you could find any device that actually reports in kPa instead of PSI (pounds per square inch).

For me, adapting my thinking has actually been the easiest part of the process. I spent more effort updating the hardware and software I use. That was like a more pervasive and annoying (but thankfully one-time) version of the annual daylight savings clock reset dance.

Computer changed? Check. Cell phone OS? Check. Home voice assistants? Yeah, okay. Smart bathroom scale? Yup. Bike computer? Yup. All the kitchen measuring cups and spoons? Well…

There were, of course, a couple outliers. There doesn’t seem to be any way to switch our (reasonably new) kitchen oven away from °F, nor our digital medical thermometer.

And websites, too. Biking sites like Garmin Connect, Strava, and Elevate? Yup. U.S. National Weather Service? Perhaps surprisingly, you can only change to international units on a couple of their pages, not all of them…

And then I had to make some updates to various software that I’ve written myself. My cycling database and spreadsheet and charts needed a few tweaks. I had to change the weather menubar widget I wrote to report out in metric. And the same for the program that appends weather and ascent data onto my Strava bike ride logs. And so forth.

Rather than me, the biggest inconvenience has been to Inna, who now has to explicitly ask our home voice assistant for temperatures in Fahrenheit (aka “little degrees”).

But for me, aside from a couple hours switching devices and program outputs, switching to metric was pretty effortless. So effortless that it makes the past sixty years of vociferous American hand-wringing seem stubbornly wrong-headed.

After all, 28.35 grams of prevention is worth 0.45 kilograms of cure…

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Ornoth

Binary Digits

Metrics of Success