Non-packed base  - 001100010011001000111000

Packed base      - 10000000
Three for or     - 00000011
Base now         - 10000011

Revised base 138 - 10001010
Flip mask        - 00000111
Flipped base 141 - 10001101

Unset mask       - 11111111
Cleared base     - 00000000

Set mask         - 10000000
Set high bit     - 10000000

Set mask         - 00000011
Set two lowest   - 10000011

Flip mask        - 00001111
Flip four lowest - 10001100

Set mask         - 00000111
Set three lowest - 10001111