x86 programming for Ms Dos Computers in CGA , EGA and VGA!

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...





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

Amstrad PC1512 IBM Compatible

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!

CGA color Palette


Palette 0 Dark Palette 0
Bright
Palette 1 Dark Palette 1 Bright
0



1



2



3




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






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
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
b7 b6 b5 b4 b3 b2 b1 b0

 

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