## Ep 104: A bit of history

## Ep 103: Tierra, bits bytes and life

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##### Tierra, bits bytes and life

In the early 1990/s, a biologist named Thomas Ray created a computer program that acted like a computer infected with many little programs. He called it Tierra, Spanish for “Earth.” The little programs could, and did, mutate, self-replicate, and evolve in strange and wonderful ways.

Here’s the home page for Tierra.

Here’s a good article about Tierra.

Artificial Life – Tools Ideas Environment

And here’s a nice video on the Tierra system, and the story behind its creation.

## The prime, and only, directive.

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There seems to be a tradeoff.

On the one hand, you can have a complicated machine, and easy programming.

On the other, you can have a simple machine, but the programming gets weird and obscure.

…

## Ep 102: Core Wars

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##### Core Wars

In 1984, the game Core Wars was written and introduced to the public. Contestants write programs in a special language called redcode, and attempt to halt or overwrite the other programs in order to be the last game standing.

Here’s a beginner’s guide to redcode

The beginners’ guide to Redcode

Here is a link to a page that has html versions of the original scientific American articles that introduced the game.

A. K. Dewdney’s Scientific American Articles on Core War

Here are a couple more links to pages about the game.

## Ep 101: Darwin, the game

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##### Darwin, the game

In the summer of 1961, a game was created. It was a programming game. Players would write programs that would compete against one another to try and copy themselves as often as possible, and attempt to deactivate the other programs.

Here are a couple of links with more information on the game.

## Ep 100: Meanwhile, elsewhere on the planet

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##### Meanwhile, elsewhere on the planet

I wanted to do something special for episode 100. It snuck up on me, and I never figured out what to do. I decided to share a couple of other projects, outside of the podcast.

One is a blog series I’m working on, about how computers compute.

The other is an experiment with digital life.

No link for the latter as of yet. Stay tuned!

## Ep 99: 256 simpler games

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##### 256 simpler games

In the 1980/s, Stephen Wolfram began considering and experimenting with elementary cellular automata. These are, instead of a 2-dimensional grid, just a one-dimensional row of cells or squares. At least one of these simpler games, rule 110, turns out to be Turing complete, just like Conway’s game of life.

Here are links to more information about rule 110.

The Significance of Universality in Rule 110

Here’s a link to the online atlas of elementary cellular automata.

Wolfram Atlas: Elementary Cellular Automata

Here’s a link to Stephen Wolfram’s book on the subject.

And last but not least, here’s a link to a page about an experiment, that includes some cellular automata you can listen to. The active cells have been mapped to notes on a musical scale.

## An alphabet you know

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It’s Monday morning. I’m sitting at my desk, using my fingers to hit keys in more or less the right order. I’m using 26 letters to construct words and sentences in order to convey my meaning. Well, 26 letters, and the spellcheck.

An alphabet is a collection of symbols that can be combined to form words. The words can then be combined to create phrases, sentences, paragraphs and pages. It’s a flexible design that allows comparatively few symbols to be used to capture and share a language, a considerable improvement on other writing systems that use a different symbol for each word. Still, if you want a machine to react to what you’re writing, 26 letters aren’t enough, or, if you squint at it another way, 26 letters are far too many.

If you look at the two first paragraphs of this section, or any of the rest of this, you’ll notice that the letters a through z aren’t the only symbols I’m using. I’ve got periods and camas, and the occasional apostrophe. For a machine to be able to follow a language, it needs every last symbol you’re going to use to be a part of its alphabet. That includes an empty space—the symbol used to separate symbols into groups. In fact, even lower-case letters, (a, b, c,) are distinct from uppercase letters, (A, B, C,) which doubles the number of letters, to 46, plus all the other symbols I just mentioned, plus all the others that I didn’t.

The English alphabet started as a sort of shorthand way of writing. The Egyptians needed a way to write instructions for their workers. They came up with a phonetic system that was much quicker to learn and easier to use than their hieroglyphics. Later, the Phoenicians picked it up. Then, they passed it along to the Greeks.

The Greek language didn’t use every sound that the Phoenicians or Egyptians did. They took the symbols for sounds they didn’t use, and changed them into vowels. Combining vowels with the Phoenician consonants, they could represent every sound used in their language with fewer symbols, and it gave them a way to try and approximate sounds from other languages. Later still, the romans added a couple of other letters to cover sounds they used that the Greeks did not. Still later, the Roman alphabet turned into the beginning of the English one, along with several others.

Alphabets, like the languages they represent, change over time. At any given moment, someone somewhere could draw some new character and toss it into the mix. Even if your basic alphabet doesn’t change, you and your folk might get into something like engineering, or mathematics, or logic, and suddenly there’s a mess of folk, inventing new symbols left and right. If you need to include every symbol you’ll use in the machine’s alphabet, and new symbols may be added, your poor confused computing contraption will need an alphabet that includes all possible symbols.

Let’s see… That’s 26 lowercase, 26 uppercase, all the numbers, all the punctuation marks, spaces, indents… and every other possible symbol. I think that’s infinite.

There is an easy way to represent all possible symbols.

Take the symbols, letters and so forth, and map them to numbers. A simple version is to take the letters of the English alphabet, and number them, 1 through 26.

A=1, b=2, c=3… z=26.

So, “8 5 12 12 15” is the same as “hello”

we need spaces between the numbers to let you read them, but what if we want there to be a space between one word and the next? we’ll need a number to represent a space, say 27.

“8 5 12 12 15 27 23 15 18 12 4” means “hello world”

We’ve got quotation marks, which could be mapped to 28.

28 8 5 12 12 15 27 23 15 18 12 4 28 means “hello world”

Whenever we want or need a symbol that hasn’t been included, we can use the next number. Which number is mapped to which symbol doesn’t matter, so long as it’s consistent. To keep things simple, one can avoid fractions and the like. Using only whole numbers, all possible numbers can be written with an 11-symbol alphabet—0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and a space. The number of whole numbers is infinite, so we can use 11 symbols to represent an infinite number of different symbols.

In typical computer design, your system represents all the letters and such you see, and various and sundry commands with numbers. If you want the computer to add two numbers, for example, it will send those numbers to a couple of specific spots in the machine, and another number that means, “Add those for me,” to another specific spot. Then, it can fetch the answer from yet another spot. To be sure the right number goes to the right place at the right time, the places where numbers can be sent have addresses, which are also numbers.

The simplest possible alphabet consists of only two symbols. If you have one symbol represent a zero, and use the other to represent a one, you can represent all possible numbers with just two symbols. Because of the way computers store numbers, you don’t even need a special character to represent a space.

It’s easier to design for a two-symbol alphabet, but the simplest alphabet isn’t always the simplest to follow. We’ll be using integers—positive and negative whole numbers. Keep in mind that our contraption will see these as zeros and ones, but we’ll get to how that two-symbol alphabet, called binary, actually works in later sections.

Before we start to design our contraption, let’s take some time to figure out how it will be programmed—how we can tell it what to do. Because, if we don’t give it a program to run, it will sit there, fires stoked, billows of steam drifting picturesquely through the air, and do nothing.

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## Ep 98: Conway’s game of life

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##### Conway’s game of life

In the previous episode we talked about cellular automata, and John von Neumann’s self-replicating system. While he used cellular automata with 29 different states for each cell, a much simpler game is capable of creating self-replicating systems. A British mathematician created his game of life in the 1950/s. In 1970, an article in “Scientific American” popularized his game. Since then self-replicating patterns, and universal computers have been created within his game.

As I mentioned it in today’s episode, here’s a link to my blog series on how computers compute.

Water or steam? to build my computing machine?

Here’s a page that provides a nice overview of the game of life, and how a Turing complete system can be constructed within it.

The Wild World of Cellular Automata

Here are a couple of catalogs of different interesting patterns within the game.

Here are a few universal computer patterns that have been created.

A Turing Machine in Conway’s Game of Life, extendable to a Universal Turing Machine