Error in tutorial #10...

atc · Thu Feb 04, 2010 5:39 pm

This tutorial has an error in it: http://www.brokenthorn.com/Resources/OSDev10.html

Quote:

The attribute byte is a byte that defines certain attributes, and defining both foreground and background colors. The byte follows the format:

* Bits 0 - 2: Foreground color
o Bit 0: Red
o Bit 1: Green
o Bit 2: Blue
* Bit 3: Foreground Intensity
* Bits 4 - 6: Background color
o Bit 4: Red
o Bit 5: Green
o Bit 6: Blue
* Bit 7: Blinking or background intensity

Bits 0 -2 & 4 - 6 are actually backwards for some reason, so it should read as:

Quote:

* Bits 0 - 2: Foreground color
o Bit 0: Blue
o Bit 1: Green
o Bit 2: Red
* Bit 3: Foreground Intensity
* Bits 4 - 6: Background color
o Bit 4: Blue
o Bit 5: Green
o Bit 6: Red
* Bit 7: Blinking or background intensity

Yes, it does seem odd. Until you think of it like the way we read English, right to left. So you'd start from bit 7 and read to bit 0, thus reading the color bits as R,G,B!

0x9A or 10011010b -- You get blinking green text with blue background.
Then try...
0xCA or 10001010b -- Same thing, but red background.
0x11 or 00010001b -- Totally blue, can't even see it if you have blue BG!

Not so weird when you think about it, is it? :lol:

But definitely a bit counter-intuitive when you read the bits as a number (sorta Little-Endian-ish, lol), rather than the way we read English words. This doesn't mean there's anything wrong with the author, it means there's something wrong with INTEL! :lol:

Author	Message
atc Joined: Sun Jan 24, 2010 2:20 pm Posts: 23	Error in tutorial #10... This tutorial has an error in it: http://www.brokenthorn.com/Resources/OSDev10.html Quote: The attribute byte is a byte that defines certain attributes, and defining both foreground and background colors. The byte follows the format: * Bits 0 - 2: Foreground color o Bit 0: Red o Bit 1: Green o Bit 2: Blue * Bit 3: Foreground Intensity * Bits 4 - 6: Background color o Bit 4: Red o Bit 5: Green o Bit 6: Blue * Bit 7: Blinking or background intensity Bits 0 -2 & 4 - 6 are actually backwards for some reason, so it should read as: Quote: * Bits 0 - 2: Foreground color o Bit 0: Blue o Bit 1: Green o Bit 2: Red * Bit 3: Foreground Intensity * Bits 4 - 6: Background color o Bit 4: Blue o Bit 5: Green o Bit 6: Red * Bit 7: Blinking or background intensity Yes, it does seem odd. Until you think of it like the way we read English, right to left. So you'd start from bit 7 and read to bit 0, thus reading the color bits as R,G,B! 0x9A or 10011010b -- You get blinking green text with blue background. Then try... 0xCA or 10001010b -- Same thing, but red background. 0x11 or 00010001b -- Totally blue, can't even see it if you have blue BG! Not so weird when you think about it, is it? But definitely a bit counter-intuitive when you read the bits as a number (sorta Little-Endian-ish, lol), rather than the way we read English words. This doesn't mean there's anything wrong with the author, it means there's something wrong with INTEL!
Thu Feb 04, 2010 5:39 pm

Mike Site Admin Joined: Sat Oct 20, 2007 7:58 pm Posts: 359	Re: Error in tutorial #10... Hello, I believe you are correct, sorry for the error. It will be corrected _________________ Lead Programmer for BrokenThorn Entertainment, Co. Website: http://www.brokenthorn.com Email: webmaster@brokenthorn.com
Sat Feb 06, 2010 12:23 am

atc Joined: Sun Jan 24, 2010 2:20 pm Posts: 23	Re: Error in tutorial #10... Ah, no need to apologize, my friend! With such a huge series, this sort of thing will happen to any writer. We thank you for the series!
Sat Feb 06, 2010 3:10 am
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