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Text Kernel

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cd-w

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It has been nearly a year since I updated this blog, and just about as long since I did any Atari programming. However, things are a bit quieter for me at the moment and I decided to write a text kernel as a way to refresh my 6507 programming knowledge. My first attempt is attached to this message and is an extension of the Juno First title screen technique in my previous blog entry. The screen-shot below shows the results - I have managed to get 12 lines of nearly flicker-free text (24-chars wide) on the screen:

 

blogentry-6563-1201689929_thumb.png

 

I would be happy with this if it weren't for a much better text kernel that supercat posted recently, which gets nearly twice as many lines of text on-screen. As a result, I'm going to try to improve this code to see if I can squeeze in a few more lines. I'll post the results here if I manage to make any improvements.

 

Chris

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Looks good to me! (For what it's worth, I like a little extra space between the lines.)

 

How difficult would it be to make a text kernel that supported upper and lowercase?

 

The reason I ask, is that it's easier to read than just uppercase alone. So for a text adventure, it would be more desirable. Plus, with lowercase support, you can add things like SHOUTING to the text. ;)

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Without knowing how the RAM and ROM requirements of the two text kernels compare, "better" might be a little subjective.

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Looks good to me! (For what it's worth, I like a little extra space between the lines.)

How difficult would it be to make a text kernel that supported upper and lowercase?

The reason I ask, is that it's easier to read than just uppercase alone. So for a text adventure, it would be more desirable. Plus, with lowercase support, you can add things like SHOUTING to the text. ;)

 

This text kernel supports 256/4 = 64 separate characters - enough for both upper and lower case letters, numbers, and a couple of symbols. I'm not a big fan of text adventures, so I probably won't be writing one any time soon, but this kernel would be good for game instructions etc.

 

Cheers,

Chris

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Without knowing how the RAM and ROM requirements of the two text kernels compare, "better" might be a little subjective.

 

I agree, but I still have no idea how supercat managed to squeeze in 26 characters per line!

 

Chris

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How difficult would it be to make a text kernel that supported upper and lowercase?

 

To minimize flicker, uppercase letters should be 7 or 11 lines tall. Lowercase letters should probably have an even height but should certainly not have a height of 5. On a 7-line "E", the top and bottom lines will flicker opposite the middle ones. On a 5-line "e", all three horizontal strokes would flicker together.

 

Further, for purposes of my pre-paired letters kernel, adding upper and lower case would increase the number of different character pairs required.

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