D-108

v-2.5.0c
---
1. change messages => while button being pushed

    ==> w
W
D-108

v-2.5.2a
---
1. display => convert hex num into character code
2. 1-digit hex

    ==> done
D-108

v-2.5.2b
---
1. display => convert hex num into character code
2. 2-digit hex

    ==> done
D-108

v-2.5.3a
---
1. convert => hex to decimal
2. experiment => RRF

    ==> started