Roman Numerals

Roman numerals are the name given to the numeral system used in ancient Roman times (especially in the time of Caesar), read from left to right it uses 7 letters whose values are added or subtracted according to their position.

Roman numeration uses 7 letters corresponding to 7 numbers. Roman digits chart from 1 to 1000:

I	1
V	5
X	10
L	50
C	100
D	500
M	1000

Beyond several thousands, there are no letters to represent these numbers.

However, some archaic scripts (more rare) used 4 other symbols

Ɔ	500
ↀ	1000
ↁ	5000
ↂ	10000

Roman numeral system uses two rules:

— (1) Any letter $ L_2 $ placed to the right of another letter $ L_1 $ are added if $ L_2 \leq L_1 $

— (2) Any letter of unit $ L_1 = \rm{I} $ placed immediately to the left of another letter $ L_2 \neq \rm{I} $ is subtracted.

Rule (2) is sometimes extended to: Any letter $ L_1 $ placed immediately to the left of another letter $ L_2 > L_1 $ is subtracted.

In theory therefore, any symbol (letter) is repeated a maximum of 3 times consecutively.

The program automatically detects whether the number is in Arabic or Roman numerals and makes the conversion/translation.

Roman numeration does not permit writing large numbers, beyond 9999 the program will display the number of thousands separately. This writing is not standardized but remains comprehensible.

The program is very permissive and allows badly formed Roman numbers not complying with the rule (2).

Romans did not use the zero, for them it was not a digit but a state of emptiness, so they did not write it (the absence of a number indicates zero).

Four is written IV, however, this software indicates that IIII = 4, unusual, IIII is a variant of IV which is tolerated. It can be found today (typically in watches, or clocks).

There is no specific way to write a date (or a birthdate), except to write the number of the day, the month and the year separately.

dCode has a tool to write a date in latin.

In some European countries, the centuries are sometimes written in Roman numerals.

Numbers above 10000 were not thinkable, without any calculation tool, they were useless. If you wish to write a value of hundreds of thousands, one can imagine writing hundreds of M at the beginning of the number.

The negative writing is not recognized, it probably did not exist. The notion of positive or negative numbers is related to the concept of zero (which was not known to the Romans).

However, today, adding a - can help to be understood.

Using decimal numbers is very few documented in history books, however, it is probable that they used fractions, including a duodecimal currency system (base 12) which allowed sharing by 2, 3, 4, 6 and 12 without decimal places.

Roman numerals were born with Antique Rome, so starting at the 7th century BC. For example, they were used with Latin.

Roman numerals have been added to the Unicode standard, they encode by a single character each number from 1 to 12 (used in clocks and watches) and 8 other numbers meaning:

Unicode character	Value	Unicode character	Value	Unicode character	Value
Ⅰ	1	Ⅱ	2	Ⅲ	3
Ⅳ	4	Ⅴ	5	Ⅵ	6
Ⅶ	7	Ⅷ	8	Ⅸ	9
Ⅹ	10	Ⅺ	11	Ⅻ	12
Ⅼ	50	Ⅽ	100	Ɔ	500
Ⅾ	500	ↀ	1000	Ⅿ	1000
ↁ	5000	ↂ	10000

Roman numerals can be written with 4 identical letters in a row, but this is rare or incorrect.

Roman numerals are learned at school in primary school but are rarely used except in mathematics or history. The uses today are limited to clocks, dates, but also on tattoos, many tattoos use Roman numerals.