Holiday Lights

HOLIDAY LIGHTS 

My earliest memories of Christmas are all about the lights. In the early 1960's, the Christmas tree was wrapped with strands of small, colored, incandescent light bulbs that were roughly candle flame shaped and held by miniature screw sockets. These hot little things were always turned off when no one was around. They were so hot there was always the risk of the cedar tree would burst into flame. Only a few years earlier people hunted down cedar stumps in the woods and dug up the wood to be used as ``lighter''. Cedar trees burn well. 

The colored lights reflected off hundreds of tinsel hangings, giving the tree an other worldly affect. I would lie on the floor and lookup through the tree getting the maximum effect of the splendor. We would usually keep the other lights in the room turned off, the room lit only by the red, greed, and blue small bulbs of the tree being deflected in all directions by the tinsel. To me the tree was all about the lights.  

Since as early as I can remember I have been fascinated by how things work. How did these small candle flame shaped objects make their light? At one level I knew the light came from the electricity since the strings of lights were plugged into the wall. But how did the invisible current turn into this glorious pleasure trove for the eyes. 

I was that kid who broke everything because I took everything apart to see how it worked. Nothing that had a screw was safe. I must have been very annoying. I busted one of these bulbs open, but other than learning how sharp the thin jagged bulbs were, and how to put on a band-aid, how the bulb worked remained a mystery. 

It was only years later in college physics class did I learn that light was the byproduct of electrons giving off energy as they dropped to a lower shell in the tungsten atoms. The electrons had been moved to the upper shells as they rushed through the filament. 

For a time when I was in high school I wanted to be an electrical engineer. I wound up going to the University of Georgia, a liberal arts school, which was only twenty minutes away, instead of the famous Georgia Tech. The trip to Tech was a couple of hours away, too far to commute from home. 

At UGA I fell in with the software crowd and my hardware aspirations were deferred. But, even though I was doing software, I still wanted to know how the hardware worked. All roads led back to that minute particle the electron. This tiny particle, and 0.0000...(25 zeros omitted)...09109 Kg is pretty small, makes not only light, but it makes everything we do in computing work, especially the central character of computing, the transistor.

But my journey to understanding them was in steps. 

I learned computer science from the top down. First, just how to write programs, then how to use programs to create applications, using data structures and databases. Eventually, I learned how compilers and operating systems worked, how to write device drivers and how to use assembly languages, how the processor, memory, network devices, and disk controllers were programmed. 

As I journeyed deeper into the ideas of the craft, I learned the register transfer level of design. In the mind of the designer, computers et al were built of registers and how the data in them are moved around, transforming the data as it dances to the metronome of system clock. 

As I dug deeper I learned registers are made of logic functions, usually a NOR (Not Or), that's looped back on itself, making it a stable multivibrator, called a flip-flop. 

So the register transfer level design is reduced to a logic design using logic gates of AND, OR, NOT functions. Everything is based on those three functions. How does the integrated circuit that implements those? 

In the most common cases today, CMOS, uses a pair of transistors. Transistors are made on a single piece of perfect crystal with impurities added to crystal lattice to create charge carriers. Some of the Silicon gets bits of boron impregnated in it, and other parts have some phosphorus cooked in. The boron makes the area have more electrons than needed, and the phosphorus create places for electrons to go, called holes. 

A magnetic field created by an extremely tiny plate of metal or, these days, something called polysilicon, creates a charged field that changes the the behavior of the impure silicon underneath it. The field will turn off silicon that conducts, or turn on silicon that doesn't. These pair complement each other. One transistor connects to power and the other to ground. The simplest form, with these two transistors, form a NOT function. Add a couple more and you can make a NOR, or NAND (Not AND). If you can make a NAND or a NOR, you can build all the logic functions. 

I'll stop there, but it's actually neat how the impure silicon actually passes or blocks electrons. 

That's a long way from my Childhood. My faith is as well. While there is always more to learn, I think I also understand Christmas. Truely the historic birth of Jesus leads to peace on earth and good will to men, all men. 

It is my since prayer that you will have a very Merry Christmas, and a Happy New Year, that you're 2018 will be great as Coraid's. 

May God shine his light upon you.