Apple-2-SW
/
bitmap-editor
mirror of https://github.com/tilleul/apple2.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Update README.md

This commit is contained in:
tilleul 2022-09-25 19:45:14 +02:00 committed by GitHub
parent 2fbcbf88e8
commit b5a0903abf
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 5 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
stranger_things/003 - Inline Text Modes/README.md
View File

@ -107,7 +107,7 @@ POKE 1024,1 : POKE 1025, 65: POKE 1026, 129: POKE 1027, 193
Well ! It looks like we can store values of 128 to 159 on the screen memory even though we cannot PRINT those control-characters.
## Why print control-characters ?
Let's admit it, at first sight, there's absolutely no interest in printing control-characters. After all, these characters are designed to be invisible: they're used in communications protocols or to move the cursor, etc. What's more they just look like normal characters when you POKE them in screen memory.
Let's admit it, at first sight, there's absolutely no interest in printing control-characters. After all, these characters are designed to be invisible: they're used in communications protocols or to move the cursor, etc. What's more they just look like normal characters when you `POKE` them in screen memory.
Well, there's one minor interest though. The text area memory is in $400-$7FF. And this area is shared with the lo-res display. It means we can use `PRINT` to `PLOT` on the lores screen. `PRINT`ing one character actually draws two contiguous vertical lores pixels.
@ -116,7 +116,10 @@ For instance, type the following:
GR
INVERSE: VTAB 1: PRINT "Q@Q@QAA@Q@@@Q@@@QAQ": PRINT "QAQ@QA@@Q@@@Q@@@Q@Q": PRINT "A@A@AAA@AAA@AAA@AAA": NORMAL: VTAB 22
```
You've just drawn the word "HELLO" tthe fastest possible way with Applesoft only.
![Hello in lores](img/hello.png)
You've just drawn the word "HELLO" the fastest possible way with Applesoft only.
The problem now is that to `PRINT`/draw all possible combinations of colors you need to be able to `PRINT` all 255 possible values of bytes, including those between 128 to 159, that is the control-characters.