kiedyś zacznij używać mózg.
BCD and non BCD values:
Since only nibble values from 0 to 9 are valid in BCD, it's interesting to see what happens when using A to F:
$00+$0F=$15 (an easy way to convert a hex-digit into BCD...)
$00+$1F=$25 (can be claimed as being "ok" since 10+$0F=25)
$10+$1F=$35 ("ok")
$05+$1F=$2A (a non-BCD result, still somewhat "ok" since 5+10+$0F=20+$0A)
$0F+$0A=$1F ("ok", since $0F+$0A=$0F+10)
$0F+$0B=$10 (now, this is plain bullshit!)