$D018/53272/VIC+24:   Memory Control Register

   +----------+---------------------------------------------------+
   | Bits 7-4 |   Video Matrix Base Address (inside VIC)          |
   | Bit  3   |   Bitmap-Mode: Select Base Address (inside VIC)   |
   | Bits 3-1 |   Character Dot-Data Base Address (inside VIC)    |
   | Bit  0   |   Unused                                          |
   +----------+---------------------------------------------------+

   Default Value: $14/20 (%00010100).

Kernal-Reference:

 LDA $D018   : $EB59 $EC48 $EC53
 STA $D018   : $EB5E $EC58