C64 - Imapenguin

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C64

A collection of 40 posts

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

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

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

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

There's a wonderful yearly online event called Advent Of Code (#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 I can on 8-Bit

Quick Tower of Hanoi with Sound on the Commodore 64

Quick Tower of Hanoi with Sound on the Commodore 64

I LOVED Ayliean MacDonald's Tower of Hanoi video on Numberphile this week. I wanted to try it with some "soothing" sounds from the 80s with the SID from a Commodore 64 No code breakdown this time, just a little Thursday lunchtime fun I whipped up during a conference call ;-)

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, to be sure. We've used this random function in many of the Cipher series articles before, both via BASIC and directly getting randomness from the SID

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

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. 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 - 16k of RAM

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

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

Running Commodore 64 BASIC Programs on a PET

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,

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

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

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

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 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 tricks of all time, and I was

The retro pinout project

The retro pinout project

One of my main goals in sharing retro computing is to help people DO things with these machines. They are useful for all sorts of reasons, not the least of which is education and demonstration. The constraints are wonderful for this. Using 30-50 year old hardware comes at a price.

Quick Post: Modulus in BASIC 2 without a cartridge

Quick Post: Modulus in BASIC 2 without a cartridge

I posted this on Twitter a few weeks ago, but a young lady has been exploring programming in Python and also with Commodore BASIC which is pretty neato. She's 11 and asked if there was a way to do modulo functions on Commodore BASIC because she's using her Dad's VIC-20

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

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

Cryptonomicon Pontifex/SolitaireWe'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 in

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

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 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. WhyThe one time pad

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

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

HashesWe did an implementation of a once popular hashing function in Part 8 on 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 applied to the input and

Making and Breaking Ciphers with Commodore 64 Part 9 - Finding Smallish Primes

Making and Breaking Ciphers with Commodore 64 Part 9 - Finding Smallish Primes

RecapSo far we've Reversed a stringShifted bits left and right (mostly right)Brute forced a known simple cipherChanneled our inner John Connor by cracking ATM machinesSearched through a large number looking for matchesLearned how to use XOR to recover dataCreated a Linear Feedback Shift Register to generate better random numbersImplemented

Quick Post: Slow text on the Commodore

Quick Post: Slow text on the Commodore

An "almost teenager", Josh, sent me an email yesterday asking how I do slow text on the Commodore. He is just starting assembly at 12 which is pretty impressive. He's been using KickAssembler, but wants to try it "on hardware". It's not difficult really. There are probably a lot of

The Commodore 64 N.O.O.C.U.L.A.R. futbal project

The Commodore 64 N.O.O.C.U.L.A.R. futbal project

ConceptI'm fortunate to have a number of vintage computers I've collected over the years. Some were fun finds, others donated. One I've had since 1983 (we think) and it's one of my most prized possessions. I travel a fair bit and not long ago I was looking for something for

Making and breaking Ciphers on the Commodore 64 Part 8 - RC4

Making and breaking Ciphers on the Commodore 64 Part 8 - RC4

RecapSo far in this 8 part series on doing weird things with Ciphers on old computers we've: Reversed a stringShifted bits left and right (mostly right)Brute forced a known simple cipherChanneled our inner John Connor by cracking ATM machinesSearched through a large number looking for matchesLearned how to use

Repairing a Commodore 128 and DIY Chris's RAM tester review

Repairing a Commodore 128 and DIY Chris's RAM tester review

I have several items from DIY Chris that we'll review over the next week including a GAL PLA and flash-able ROM drop in that can hold kernal, character or BASIC ROMs. First on the list is the RAM tester. The problem child 128I have a Commodore 128 which developed a

Making and breaking Ciphers on the Commodore 64 Part 7 - Pseudo Random with Linear Congruential Generators

Making and breaking Ciphers on the Commodore 64 Part 7 - Pseudo Random with Linear Congruential Generators

So far in this 7 part (shocked I've made it through 7!) series on doing weird things with Ciphers on old computers we've: Reversed a stringShifted bits left and right (mostly right)Brute forced a known simple cipherChanneled our inner John Connor by cracking ATM machinesSearched through a large number

Making and Breaking Ciphers with a Commodore 64 - Part 6: XOR is Magical - Data recovery

Making and Breaking Ciphers with a Commodore 64 - Part 6: XOR is Magical - Data recovery

ReviewSo far we've: Reversed a stringShifted bits left and right (mostly right)Brute forced a known simple cipherFaked it, but then looking for a 4 digit known pinSearched through a large number looking for matchesWe now have most of the basic skills in Assembly to start doing some real work.

Finding the Prodigal Easter Egg inside the Easter Egg on a Commodore 64

Finding the Prodigal Easter Egg inside the Easter Egg on a Commodore 64

If you REALLY want to get into the weeds on how I figured out the Easter Egg(s) inside the Easter Egg on a 35 Year old album on a 35 year old computer then you're in luck! This video is for you! I mention "the original author" in the

Quick post: Determining length in Commodore Assembly

Quick post: Determining length in Commodore Assembly

A common task in our code is to determine the length of something. In this example, let's check the length of a string like "are you keeping up?" In Python, this is crazy easy. #!/usr/bin/env python message = "are you keeping up?" len(message) Python 3In 6510 Assembly, this

Benchmarking Retro Computers (mostly Commodore) with marginal methods

Benchmarking Retro Computers (mostly Commodore) with marginal methods

Just the BASICs, pleaseOur friend in retro @NoelsRetroLab has a simple BASIC benchmarking tool that's fun to use to compare different basic systems execution speed. We're counting jiffies, which is roughly (sometimes very roughly) 1/60th of a second. We're using three variations of this code on the Commodore BASIC

Jiffies in Assembly

Jiffies in Assembly

Many of you know that you can use a "Jiffy" on a Commodore as a measure of time. Sorta. The short short version is that we have a 3 byte clock that increments once every interrupt, so 1/60th of a second. It's not considered reliable as a real time