VIC-20-PEEK-AND-POKE-MULTICOLOR-COMPLEXITY
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TOOL: 		COMMODORE VIC-20 - BASIC 2
Language: 	BASIC 
Extra:		-
Author: 	Misel Zivanovic
Note:		(C) 31st DEC 2025 - www.lived.ch, mzretro.ch
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VIC-20 has access to 4 color registers when Multi-Color {low-resolution} is active! 
Which means would theoretically need 4 addresses to manage that. However, VIC-20 needs just 3 due to
the fact that BORDER and BACKGROUND COLOR and managed by only one register using LOW-HIGH Nibble color
structure.

The content of this table will help you to better understand what i mean!

VIC-20 COLOR PALETTE:
-----------------|-------|----------------------|----|----|-----------------------------------------------|
COLORS 0-7	 |dec/hex| VIC-20 COLOR LISTING |dec |hex | COLORS 0-15					  |
---------------- |-------|----------------------|--- |----|-----------------------------------------------|
LOW-NIBBLE	 | #$ 00 | 00 - Black	        | 00 |#$00| HIGH-NIBBLE {BACKGROUND COLORS}		  |
{Bits 0-2}	 | #$ 01 | 01 - White	        | 08 |#$08| {Bits 4-7}					  |
BORDER COLORS: 	 | #$ 02 | 02 - Red	        | 16 |#$10| POKE 36879,INV+{COLOR x 16}			  |
POKE 36879,X+INV | #$ 03 | 03 - Cyan    	| 32 |#$20|						  |
CHARACTER COLORS:| #$ 04 | 04 - Magenta 	| 48 |#$30| INV     = 8    NORMAL MODE			  |
POKE *38400,X+MC | #$ 05 | 05 - Green	        | 64 |#$40| INV     = 0    INVERSE MODE			  |
POKE 646,X+MC    | #$ 06 | 06 - Blue	        | 80 |#$50| COLOR   = 0-15				  |
	         | #$ 07 | 07 - Yellow	        | 96 |#$60| SND     = bit 0-3 Sound Vol. {not needed here}|
-----------------|-------|----------------------|112 |#$70|      	`				  |
* If more than	 |	 | 08 - Orange	        |128 |#$80| POKE 36878,SND+{COLOR x 16}	{Color Bit 4-7}	  |
8KB RAM then the |	 | 09 - Light Orange    |144 |#$90|-----------------------------------------------|
start address is |	 | 10 - Pink	        |160 |#$A0| How to know what is what?			  |
POKE 37888,X+MC	 |	 | 11 - Light Cyan      |176 |#$B0|-----------------------------------------------|
-----------------|	 | 12 - Light Magenta   |192 |#$C0| 00- POKE 36879,INV+{COLOR x 16}- SCREEN/BG {1}|
MC=8=Multi Color |	 | 13 - Light Green     |208 |#$D0| 01- POKE 36879,X+INV 	   - Border    {2}|
MC=0=Normal Mode |	 | 14 - Light Blue      |224 |#$E0| 10- POKE 38400,X+MC 	   - Color MAP {3}|
INV=8 Normal Mode|       | 15 - Light Yellow    |240 |#$F0| 11- POKE 36878,SND+{COLOR x 16}- MC Color  {4}|
INV=0 Inver. Mode|	 |			|    | 	  |-----------------------------------------------|
X = 0-7		 |	 |			|    |    | 						  | 	
-----------------|-------|----------------------|----|----|-----------------------------------------------|
Note that bit 3 {dec value 8} is depending on register,	  | Byte/Character/Graphics Example:		  |
responsible to enable/disable INVERSE/NORMAL MODE and	  |-------------------------------- --------------|
also to switch between NORMAL/MULTICOLOR MODE	          | 11 11 11 11  Note how horizontally one	  |
							  | 11 10 10 11  pixel is 2 bits wide!		  |
* Also the SCREEN address is going down to $1000,	  | 11 10 10 11  Basically, you have 4 horizonal  |
dec 4096 when more than 8KB RAM is available!		  | 11 00 00 11  pixels and 8 vertical pixels	  |
Default SCREEN address is $1e00, dec 7680		  | 11 00 00 11	 In praxis this is the 	regular   |
							  | 11 01 01 11	 high-resolution screen.	  |
							  | 11 01 01 11					  |
							  | 11 11 11 11					  |
							  | =						  |
							  |-----------------------------------------------|
							  | DATA 255, 235, 235, 195, 195, 215, 215, 255	  |
----------------------------------------------------------|-----------------------------------------------|

In next lesson we are going to create some Characters and Graphics elements!