How-To

A collection of 44 posts

code

Almost primes with TinyBASIC on the KIM-1 clone: PAL-1

Bill Gates has been a controversial figure in the Computer World for 50 years now. Back in 1976, he famously (infamously?) wrote a letter bemoaning what he saw as rampant piracy of BASIC. Micro Soft was selling their version of BASIC, which is quite good for a whopping $150. This

code

VIC’s Revenge, the drop-in replacement for the VIC-20 VIC chip Part 1: Introduction, design goals, and FAQs

I'm doing a year-long project to reverse engineer the output and functionality of a VIC-20's video chip, and create a drop-in replacement. At the start of this project (a few days ago), I only actually know how to do a percentage of the things I'll need to complete this project.

C64

64 Bit Addition and Products on Commodore: The Wheat and Chessboard problem

Dealing with large numbers in computing has been an attractive problem area for a long time. Using an average calculator might lead you to believe that it's too tricky for most applications. 0:00/1×But it's not that difficult. And to prove it, we're going to implement this calculation

Commodore

Vicky-20 S Video Mod Results

I'm very pleased with my PAL VIC-20 replica, the Vicky-20 [https://www.tindie.com/products/bobsbits/vicky-twenty-commodore-vic-20-pcb-replica/] . It's almost a year old and the VIC-20 that sits on my desk all the time. I've wanted the absolute best video out of this thing I could muster. This board is fortunately

C64

Yet another version of the 100 door problem; this time, let's extend Commodore BASIC to add PRINT @, shall we?

I stumbled across a ZX Spectrum version [https://www.rosettacode.org/wiki/100_doors#ZX_Spectrum_Basic] of the 100 Door problem that got me thinking. Wouldn't it be nice to have PRINT AT in Commodore BASIC? We do this in Assembly all the time. We already know from several

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Fibonacci 1-10 on the KIM-1 (and clones)

Sometimes there's an absolute joy in doing something the hard way to REALLY understand what's happening. I struggled (still struggle) with wrapping my mind around using the display on the KIM-1. The best way (for me anyway) to be motivated to learn something is to have an outcome in mind

C64

The terrible random number generation in the Commodore 64 (and 128)

Quite a while ago, I started playing with random numbers on 8 Bit machines. I don't think anyone is doing "serious" work on these machines, but playing with Ciphers and Crypto got me at least curious about how a Commodore 64 generates random numbers. There are many ways to determine

Commodore

Getting green and amber screens from a MiniPET 40/80

In mid-2021, I built a MiniPET 40/80. It's one of the best replica kits I've ever seen. Even the keyboard is wonderfully awkward to use, just like a real Chicklet PET keyboard is. Switching between ROM versions with DIP switches has been great for learning and experimenting with internals.

C64

Simple splitting the screen with two colors on the Commodore 64

Someone asked me yesterday how to very simply split the Commodore 64 screen to display two solid colors. The screen is 1000 "blocks"(character cells) starting at Hex $0400 (1024 decimal). It's 40 characters wide and 25 rows. 25 rows don't divide evenly, so we can tell the VIC register

code

A visual 100 Door Problem solution in Python

Last year, we did the 100 door problem on many platforms in BASIC and Assembly language [https://imapenguin.com/just-for-fun-the-100-door-problem-on-several-different-systems/] . The 100 door problem is: * There are 100 closed doors in a row. * You walk past the doors 100 times (100 passes) * The first time, visit every door. If the

C64

Permutations of 1 to 9 in Python, BASIC, and 6502 Assembly

Someone asked me this week if I would help him with a graph theory problem on 8-Bit machines. The first task was to get all permutations of 1 to 9. Since the total permutations is 9! (362,880) I knew this would take a while. Learning without learning, the standard

C64

Can you do Advent of Code on 8-Bit Machines?

There's a wonderful yearly online event called Advent Of Code [https://adventofcode.com/2021/] (#adventofcode). Each day there are two code challenges that follow a holiday narrative. Some of them are easy, and some of them are quite difficult. This year I've attempted to do as much of it as

C64

Dice frequency

I've been obsessed with the Random number generator on the Commodore computers for a LONG time, and I'm not the only one who is [https://www.youtube.com/watch?v=CfutqhHnVX0], to be sure. We've used this random function in many of the Cipher series articles before, both via BASIC

Atari

A week of diving a little deeper into my Atari 800XL

I'm a Commodore guy through and through. This isn't tribalism, it's what was in my room from 1983 to when I graduated High School in 1993. After my sorta failed attempt at spending the month of September with my Coco 2 [https://imapenguin.com/two-weeks-with-mostly-a-coco-2-in-september/], I decided for October to

Coco

Two weeks with a Coco 2 in September

In the inside baseball realm of vintage computer enthusiasts, a few hashtags have emerged to support one's favorite retro computers. The main one in September is #SepTandy While I've had this Tandy Color Computer 2 for many years, I've almost never used it. Out of all of my vintage systems,

Coco

Slot Game On Tandy TRS-80 Pocket Computer PC-4

One of my first ever real programs was a blackjack game I made in BASIC on a Sharp 9300 calculator to impress my Adv. Algebra teacher. I have seen the handwritten copy of this somewhere around here recently, but I'll be darned if I can't find it now. Slot Game

C64

Calculating Pi via the Gregory-Leibniz series in BASIC on the Tandy Color Computer 2

Back in March, we did a simple set of programs to brute force calculate Pi using a simple and well-known series [https://imapenguin.com/estimating-pi-with-the/]. It works, even if it's inefficient. Speaking of inefficient, it's September and that means it's time for #Septandy! I have a Tandy Color Computer 2

C64

Just for fun, the 100 door problem on several different systems

What's the 100 door problem? It's a just for fun problem in "beginning" math and computer courses. The idea is simple: There are 100 closed doors in a row. You walk past the doors 100 times (100 passes) The first time, visit every door. If the door is closed,  open

C64

Running Commodore 64 BASIC Programs on a PET

The Commodore 64 and PET are fairly similar systems. Other than a few memory location differences, many BASIC programs written for the Commodore 64 that don't use graphics can run on a PET. There is one caveat. The PET doesn't relocate a saved BASIC program to the beginning of BASIC,

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The CERBERUS 2080

A few months ago, I stumbled on a project that really caught my attention. Mr. Bernardo Kastrup, aka TheByteAttic [https://www.thebyteattic.com/#!] finished a video series on a computer he designed and built "by hand [https://www.youtube.com/watch?v=1ASspLiE39g&list=PLDf2uklC__d2DAXmF9XuOq_-uNc2M9ITd] ." It's an impressive

C64

Making and breaking Ciphers on the Commodore 64, er VIC-20 - Lagged Fibonacci Sequence and a little Monte Carlo while embracing contraints

We're on ANOTHER random number generation technique today. Let's work on the Lagged Fibonacci Sequence, a fun way to use the Fibonacci Sequence on itself to generate pseudo-random numbers. One of our long term goals is to add a bunch of tools to our toolbox. Making reusable components makes doing

C64

Running the 8 Bit Show and Tell VIC-20 Super Expander Programming Challenge on the Commodore 64

One of my favorite videos on the whole internet lately is this hidden gem [https://www.youtube.com/watch?v=u0ERlESbErE] by Robin. In it, he executes a programming challenge he found on Twitter to draw a pattern without using IF statements. His approach is one of my favorite math

C64

Making and breaking Ciphers on the Commodore 64 Part 12 - Pontifex - Solitaire from Cryptonomicon

Cryptonomicon Pontifex/Solitaire We're back to my favorite book for another round. We've done quite a bit with Cryptonomicon so far. One of my favorite moments is when Enoch Root introduces a cipher that two prisoners used to communicate using just a humble playing card deck. Drawing of the mine

C64

Making and breaking Ciphers on the Commodore 64 Part 11 - One time pads on a Commodore 64, probably a bad idea

A while ago, I explained in detail how to generate one time pad sheets [https://imapenguin.com/simple-unbreakable-encryption-with-a-pencil/] and use them to encrypt and decrypt messages. It turned out to be doable, only requiring a pencil and a way to create random numbers, but it's slow, error prone and tedious.

C64

Making and breaking Ciphers on the Commodore 64 Part 10 - Finding hash collisions with a type in game from 1984

Hashes We did an implementation of a once popular hashing function in Part 8 on RC4 [https://imapenguin.com/making-and-breaking-ciphers-on-the-commodore-64-part-8-rc4/] without really going into why. A hash function is any function that is used to map data of an arbitrary size (input) to a fixed size output. An algorithm is