IntyBASIC Magic Numbers for Colors?

[First Spear]

I have these two lines of code to put something on the backtab, and then set the color.
I want to put it into one line; can anyone (1) condense the code and (2) point me to a reference so I can understand more?

#BACKTAB(#varc) = $0807 + (#vara* 4 + #varb) * 8
#BACKTAB(#varc) = (#BACKTAB(#varc) AND NOT $0007) + CS_TAN

[carlsson]

Since you refer to CS_TAN, I suppose that means you're operating in Color Stack mode.

    13   12   11   10    9    8    7    6    5    4    3    2    1    0   
  +----+----+----+----+----+----+----+----+----+----+----+----+----+----+ 
  |Adv |FG  |GRAM|   Card # (0-255 for GROM,             |   FG Color   | 
  |CS  |Bit3|GROM|           0-63 for GRAM)              |   Bits 0-2   | 
  +----+----+----+----+----+----+----+----+----+----+----+----+----+----+ 

Bits 14-15 are not used.

$0807 equals Adv CS = 0, FG Bit 3 = 0, GRAM/GROM = 1, Card # = GRAM 0, FG Color = 7 (binary 111, equals CS_WHITE)

To that you add #vara * 4 + #varb, multiplied by 8 so it selects a GRAM card insteaf of affecting the colour. Finally you set FG Color to CS_TAN = $0003 (binary 011)

I would say that if this one liner should do the same thing:

#BACKTAB(#varc) = $0800 + (#vara * 4 + #varb) * 8 + CS_TAN

See also this reference: http://wiki.intellivision.us/index.php?title=STIC

Edited April 24, 2018 by carlsson