Colr Attrbt (and 15)

 BBS: Inland Empire Archive
Date: 07-28-92 (21:58)             Number: 135
From: RICK PEDLEY                  Refer#: NONE
  To: BRYAN HOOVER                  Recvd: NO  
Subj: Colr Attrbt (and 15)           Conf: (2) Quik_Bas

 On 07-28-92 Bryan Hoover wrote to All...

 BH> Can anyone explain how works the formula, ForColr% = Atribute% AND 15
 BH> ?

 BH> What's happening with the AND operator and the number 15?

The attribute value is calculated by multiplying the background color
by 16 and adding the foreground color.  So to get the foreground
color by ANDing the attribute with 15:

Fg = 11
Bg = 1        'Attr = Bg * 16 + Fg
Attr = 27     'in binary is    00011011
              'AND with 15     00001111
                               --------
                               00001011 (which equals 11 decimal)
      0|1
     -----
   0 |0|0|
     --+--
   1 |0|1|
     -----
 AND truth table


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