More ZX81 Thoughts

May 2, 2019

I've already described the first personal computer that I owned, the Sinclair ZX81, but I had some more memories to go with that post.

The amount of memory (RAM) that the computer had was 1K, that's 1,024 bytes of memory. Take out just over 100 bytes for system usage and you ended up with around 900 bytes of memory for your program and its data. My current desktop computer is about a million times more powerful than the ZX81 with its 24 Gb of memory but back then the few home computers available came with only a small amount of memory.

An additional memory pack was available for the ZX81. It was known as the Ram Pack and it brought the memory capacity up to 16K of RAM. Unfortunately, its connector was not very well designed and it literally just plugged straight into the edge of the circuit board inside the ZX81. The result was that it would wobble if you bumped the computer and would cause the computer to crash. Owners of Ram Packs tried many different ways to keep their computers from crashing. I had the most success with resting my computer on a small book to keep the Ram Pack in the air and prevent it flexing on the surface of my desk.

Without a disk drive, the way that you got programs into the computer was either by typing them in through the flat membrane keyboard or by playing recorded programs into its audio interface via a jack plug from a tape player. If you've ever heard the sounds a modem makes, that's what the programs sounded like. The programs were quite short, so it quickly became possible to buy C15 cassette tapes, that were just 15 minutes of total recording time, seven and a half minutes each side. I used to reuse the program tapes to record songs off of the radio during the chart countdown show on Sunday afternoons so I could listen to them during the week. Sometimes I would listen to the songs while going to bed and it was not unusual to be jolted at the end of a song by the screeching sound of a program that was on the tape before I recorded a song onto it.

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Cover Song - I'll Fly Away performed by Go Fish

April 23, 2019

I love old hymns, but I dislike covers of them done in country-style, so this means that there are very few hymns I can listen to on YouTube. One of my favorite hymns is I'll Fly Away. I've previously shared the awesome Christian Celtic Punk version by Flatfoot 56 and still love it, but then after some more searching I discovered that Go Fish have a great version together with a fun video. It's a much lighter version than that by Flatfoot 56 and includes a very nice guitar solo that I honestly don't remember being in the brown hymnal that we sing from at church.

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My First Computer - Sinclair ZX81

April 22, 2019

Sinclair ZX81

Image from Wikipedia page for ZX81

Back when I was a lad, I started learning about computers at school. There was no official computer curriculum, but one of the physics teachers started a computer club, brought in a couple of his home computers and started teaching interested students how to program in BASIC. I was one of those students and I fell hard for the subject of computer programming and started spending many of my lunch breaks at the physics lab working my way through the manuals that the computers came with back then.

The computers that our teacher brought in were a Sinclair ZX80 (the forerunner to the ZX81) and the Acorn Atom. The ZX80 had 1K of memory, while the Atom rocked a massive 2K. Both computers had their own version of the BASIC programming language built into the computer. Home computers, at that time, did not have floppy disk drives, so the provided programming language was invariably burned into Read Only Memory, known as ROM, so that it was available as soon as the computer was turned on.

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The Whole Armor of God

March 16, 2019

I preached last week on the need for Christians to armor up against the challenges of life and to protect their hearts. Last week's main scripture was from the Proverbs. There are plenty of scriptures that speak to the importance of protecting ourselves, but this one particularly stood out to me this time.

23 Keep thy heart with all diligence; for out of it are the issues of life.

Proverbs 4:23

One of the natural references when addressing our need for self-protection is The Whole Armor of God. I didn't have enough time to go deep into it during that sermon, so this week it gets its own time in the spotlight.

When reviewing the passage in entirety, I was struck by how logically it was organized. Now, this is the writing of the Apostle Paul we're talking about, so a certain minimum level of awesomeness should be assumed, but here the organization was so on point that it leaped out at me. As a computer programmer by training, I succeed or fail by how I logically arrange the internal structure of my computer programs, so I recognize good organization and dependency management when I see it.

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Even More School Bus Thoughts

February 22, 2019

Time is rushing by and I'm into my fifth month of driving a school bus. The changes are subtle, but noticeable. I am mostly over my fear of reversing. I still don't enjoy it, but I don't get nervous. Recently, I had to reverse about a third of a mile along a country road, around two corners and down a hill, when my only available turnaround point was not plowed out and was too full of snow for me to safely use. I wouldn't want to do it on a regular basis, but I did it and that pretty much put the final nail into my fear of reversing.

Despite my bad memory, I have both of my current routes memorized. I drive Blue in the morning and Purple at night and know where to go, when to be there and am making good progress learning the names of my students. For some reason I remember more naughty student names than good ones.

Having driven for far too many years on the Madison Beltline I've seen my share of bad American driving, but at the helm of a school bus I've had a grandstand seat to witness some awful driving. (Ok, not as bad as the Russians, but pretty bad. Search on Youtube for Russian dashcam footage, but be warned that it's scary stuff.) There are three main things that people are getting wrong. First, they are failing to understand the warning and stop lights on the school bus. I'm pretty sure that's in the driving test around here, but it feels like most drivers skipped class that day.

School buses in the United States have two sets of lights. The lower lights, those at the same approximate level as the main headlights and the upper lights near the top of the bus. The lower lights are exactly the same as all other road vehicles: headlights, indicators, brake lights and reversing lights. They all mean exactly what they mean in every other vehicle and there are no legal mandates concerning them. The upper lights are specific to U.S. school buses and are known as the student lights. There are set of amber (sometimes called yellow) lights and a set of red lights. These lights flash when in operation, are important and under penalty of law must be obeyed by all other road vehicles. The flashing amber student lights mean that the bus is getting ready to slow down and stop for a student pickup or dropoff and so you should start slowing down and be prepared to stop. When the flashing red student lights mean that the bus has student activity (getting on, getting off and possibly crossing the road) and you must stop and wait at least 20 feet away until the red lights stop flashing. There are expensive fines for not stopping for a school buses' student red lights, so please do your wallet a favor and stop.

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