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Post by Jeff Ledger on Dec 29, 2007 23:56:21 GMT -5
Could someone who understands the C64 better than I explain the nature of the screen editor in the 64? As I understand it, each change of the screen was a direct change in screen memory? Something far ahead of the competition at the time. The reason I'm trying to understand it, I would like to replicate it on the Prop.
Thanks Jeff
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Post by David Murray on Dec 31, 2007 10:28:24 GMT -5
I uderstand it pretty well, but I'm not sure what part you have a question about. In fact, I'm a bit confused by that statement "Something far ahead of the competition at the time." Because as far as I know, the only systems that didn't do it this way would be the Atari 2600 and maybe the Timex Sinclair since their screens were CPU driven.
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Post by sjgray on Jan 5, 2008 11:12:13 GMT -5
Yes, when you type, all you are doing is modifying the screen. When you press RETURN the editor looks at the line the cursor is on then "re-reads" the line(s) from screen memory and enters it into your program as if you had re-typed it. There is a "screen line link table" in zero page that keeps track of which lines wrap to the next line.
A common mistake is to edit multiple lines on screen without pressing RETURN. If you don't press return your edits will be lost.
Steve
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Post by Jeff Ledger on Jan 6, 2008 8:04:55 GMT -5
Thanks Steve... That's the description I needed!
I'm closing in on a near duplication of it now..
Jeff
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