x86 programming for Ms Dos
Computers in CGA , EGA and VGA
This page is Under
Construction.... 'Learn 8086 is planned for 2020'
The IBM 8086 took the world by storm!
Although inferior to the 68000 - the x86 soon took over, and is the
basis for all the computers we have today...
Starting with the 8086, and soon moving to the 286, 386 and so on...
each iteration has added more commands and power, and along the way
the PC has gained functionality...
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In these tutorials, we'll take a look at the early basic
machines, and learn how we can use Assembly to write games that can
be used in MSDos via DosBox!
We'll cover 3 graphics modes...
| CGA |
320x200 4 color (Cyan,Magenta,White or Green,Red,Yellow) |
| EGA |
320x200 16 color fixed palette |
| VGA |
320x200 256 color palette |
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If you want to learn 8086 get the Cheatsheet! it has all the 8086 commands, It will help you
get started with ASM programming, and let you quickly look up
commands when you get confused! |
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CGA color Palette
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Palette 0 Dark |
Palette 0
Bright |
Palette 1 Dark |
Palette 1 Bright |
| 0 |
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| 1 |
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| 2 |
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| 3 |
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EGA color Palette
The EGA system uses 16 colors - it's 320x200 can only use a palette of 16
colors (the same colors!)
Each color has a logical number from 0-16, and a Hardware number (used for
palette definitions) from 0-63
| 0
- 0 |
1 - 1 |
2 - 2 |
3 - 3 |
4 - 4 |
5 - 5 |
6 - 20 |
7 - 7 |
| 8
- 56 |
9 - 57 |
10 - 58 |
11 - 59 |
12 - 60 |
13 - 61 |
14 - 62 |
15 - 63 |
Screen Layouts
CGA is a 2bpp screen mode, it's memory is at B800:0000h
EGA use 4 bitplanes, it's address is A000:0000... to change the bitplanes
we need to OUT to 03C4h
VGA is a 8bpp screen mode, it's memory is at A000:0000h
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Bits |
| Screen
Mode |
Bits
per pixel |
Pixels
per byte |
Address |
Plane
Mask |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
0 |
| CGA
- 4 |
2 bpp |
4 |
B800:0000h |
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b1 |
b0 |
b1 |
b0 |
b1 |
b0 |
b1 |
b0 |
| EGA - 13 |
4
bitplanes |
8 |
A000:0000h |
out 03c4h,0102h |
p0-b7 |
p0-b6 |
p0-b5 |
p0-b4 |
p0-b3 |
p0-b2 |
p0-b1 |
p0-b0 |
| out 03c4h,0202h |
p1-b7 |
p1-b6 |
p1-b5 |
p1-b4 |
p1-b3 |
p1-b2 |
p1-b1 |
p1-b0 |
| out 03c4h,0302h |
p2-b7 |
p2-b6 |
p2-b5 |
p2-b4 |
p2-b3 |
p2-b2 |
p2-b1 |
p2-b0 |
| out 03c4h,0402h |
p3-b7 |
p3-b6 |
p3-b5 |
p3-b4 |
p3-b3 |
p3-b2 |
p3-b1 |
p3-b0 |
| out 03c4h,0F02h |
All-b7 |
All-b6 |
All-b5 |
All-b4 |
All-b3 |
All-b2 |
All-b1 |
All-b0 |
| VGA |
8bpp |
1 |
A000:0000h |
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b7 |
b6 |
b5 |
b4 |
b3 |
b2 |
b1 |
b0 |
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