Commodore Podcast Archives

Join me for tips and tricks on programming BASIC and Assembly on vintage Commodore systems.

Matching Lottery Numbers on the Commodore 64

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In this episode I’m amending my previous lottery number generator to take six lucky numbers from the user to match against the randomly drawn numbers from the Commodore 64. This will allow us to compare what the computer has drawn to the user’s input, as well as keep drawing numbers until the user input comes … Read more

Working with Keyboard Input in Commodore BASIC

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In this episode I’ll show you three ways to take user input from the keyboard in Commodore BASIC. The INPUT and GET commands work on all systems, while the GETKEY command only works on the Plus/4 and C128. I’ll demonstrate how to use all of them. This will come in handy for our little lottery … Read more

How to print numbers as columns in Commodore BASIC

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In this episode I’m demonstrating how to print numbers in evenly spaced columns in Commodore BASIC.

On the C128 and the Plus/4 we can use a nifty little function called PRINT USING for this, with which we can format the output of any printed text or variable.

On the C64 and VIC-20 that function doesn’t exist, so we’ll have to convert a numeric value into a string (using the STR$ function), and then determine how long our string is. Following that we’ll have to manually pad our string value with as many spaces as are required.

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Podcast: Download (Duration: 8:48 — 8.1MB)

Sorting an Array on the Commodore 64

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In this episode I’ll demonstrate how to sort a numeric array on the Commodore 64. The same principle works for string arrays, and of course on all other Commodore BASIC computers. The technique I’m using here is called Bubble Sort: in effect we’re comparing the first two items in the array, and if the left … Read more

How to generate Lottery Numbers on the Commodore 64

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In this episode I’ll demonstrate how to draw random lottery numbers on a Commodore 64. The secret sauce here is not only the RND function to generate random numbers, but also two loops inside each other that prevent the same number from coming up more than once. Here’s the lottery generator code: 10 x=rnd(-ti) 20 … Read more

How to build a Word Splitter on the C64 in Commodore BASIC

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In this episode I’m demonstrating how to build a word splitter on the Commodore 64. We’ll use string functions to parse a sentence and split each word off into an array of words so that they can be analysed later (for example, as part of an adventure game). Here’s the code I’m building: 20 input … Read more

How to build a time of day clock on the Commodore 64

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In this video I’ll demonstrate how to build a simple clock on the C64. We’ll go through this process step by step, including the built-in TI and TI$ variables, string formatting with LEFT$, RIGHT$ and MID$, as well as screen formatting. Here’s the code I’m writing – works in Commodore BASIC v2 and above: 5 … Read more

How to create random YouTube URLs in Commodore BASIC v2

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In this episode I’ll demonstrate how to create those seemingly random YouTube Video IDs using a Commodore 64. Here’s the code I’m writing – works in BASIC v2 and above: 10 print chr$(14) 20 gosub 100:x=rnd(-ti):cn=1 30 a$=”https://youtu.be/” 40 for i=1 to 11 50 rn=int(rnd(0)*62)+1 60 a$=a$+yt$(rn) 70 next 80 print:print cn;” : “;a$ 85 … Read more