Roman numerals and Arabic numbers were on some occasions written differently than the present day ones and were difficult to interpret.

Over time these Arabic numbers have steadily replaced the roman numerals.
The Arabic numbers could be understood from the context of the record and by comparing with other numbers available in the record.
Numbers on a later date were sometimes linked together.
Roman numerals were sometimes used in mentioning calender dates.

In all there are seven alphabets which are used as numbers better known as Roman numerals.

These letters could be used alone or in various combinations; and these letters are I, V, X, L, C, D and M.

Roman numerals are the number systems used long ago.
This system uses the letters which we are using in our present day counting systems.

The digits we use everyday stand alone or side by side to show certain values.

The letters standing individually gives us values such as:
I = 1
V= 5
X = 10
L = 50
C = 100
D = 500
M = 1,000

Roman Numerals is also called as the 'Ancient Rome' of number systems and is used to signify the values by combining letters from the Latin alphabet.
It does not include a zero and the cousin of Etruscan numerals.
It is an old technique which was later modified in the middle age.
In the Roman numeral system, letters represent numbers.
Roman numerals are frequently seen in early American documents and may also be found in printed sources.
These roman numerals are either written in capital or small letters.
The roman numerals 4 and 9 are written by placing a symbol of lesser value before one of greater value and so 4 would be written as IV and 9 as IX.

Let us try some examples for complex roman numerals.

1646 would be written as MDCXLVI
1751 as MDCCLI
1866 would be written as MDCCCLXVI
1917 of the Julian calendar would be represented as MCMXVII
1775 would be represented as MDCCLXXVI