Apple-2-SW/apple2_hgr_font_tutorial
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Clarify c/32

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Michaelangel007 2016-01-14 15:16:16 -08:00
parent 0c4c5f8608
commit a44148b7c1
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@ -1106,7 +1106,7 @@ Since we are dealing with a 16-bit address offset it is simpler to break this do
int AddressHi = FontAddressHi + (c / 32)
```
But since the 6502 doesn't have a division instruction we need to use bit-shifts instead. The calculation `c / 32` is the same as `c >> 5`.
But since the 6502 doesn't have a division instruction we need to use bit-shifts instead. The calculation `c / 32` = `c / 2^5` = `c / (1 << 5)` == `c >> 5`.
```c
char c = 'D'; // 0x44
@ -2795,7 +2795,6 @@ That's all folks! Now go write some cool font blitter code.
![font_codepage_437_8x8.png](font_codepage_437_8x8.png) (In progress)
- [ ] Double Hi-Res
- [ ] PDF of this document (As a work-around use Chrome and Print to PDF)
- [ ] Explains `c/32` = `c / 2^5` = `c / (1 << 5)` = `c >> 5`
- [ ] Fix mis-lable: We need to (again) touch up our `PrintChar` entry point at $0310 calling `_DrawChar2` ($034C)