Assume, while digging out an ancient site from 450 AD, you found a mysterious stone with a digital display. Your analysis finds five inputs for five segments (a
–e
) and six outputs (1
–6
). It seems to be a classic multiplexed display.
What is this display for?
What is the highest continuous sequence of numbers it can display?

In the Field
You connected the display, and it is still working. Now you can enable and disable the segments.
1 | 2 | 3 | 4 | 5 | 6 | |
---|---|---|---|---|---|---|
a | ||||||
b | ||||||
c | ||||||
d | ||||||
e |
Hints
Hint 1
Which civilisation thrived around 450AD?
Hint 2
It was the time of the Roman Empire. Which system did they use to write numbers?
Hint 3
The display can show Roman numerals. I, V, X, C, D and M. On this display, each element needs a different amount of space to be displayed correctly.
Solution
This display was made to display Roman numerals.
Sadly, the range of displayed numbers is very limited. Depending how you write the letter V
, you can count up to 16 or 17.
If you do not need a continuous sequence, the largest number is MM
.
More Challenges
- How could the display be further improved for Roman numerals?
Conclusion
I hope you enjoyed this logic puzzle. Yet, it didn't contain any logic gates, but who knows how the Romans built it 😉. Let me know if you like to see more puzzles like this.
If you have any questions, missed information, or want to provide feedback, feel free to comment below. 😄
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