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Rain · 30.10.2003., 15:00

Using Letters For Numbers
The Romans depicted numbers using seven letters of the alphabet as numerals

I = 1

V = 5

X = 10

L = 50

C = 100

D = 500

M = 1000

In some forms of Roman numbers, D is sometimes represented by an I followed by a backwards C, a bit like this I ) , and M is represented by a C followed by an I and a backwards C. This is hard to depict in a computer font as they do not contain a backwards C but it can be approximated using parentheses like this ( I ). The derivation of this form seems to be from the use of the deep parentheses to represent larger numbers. Thus ( I ) is 1000, ( ( I ) ) is 10,000 and ( ( ( I ) ) ) is 100,000.

Forming Numbers
At their simplest, numbers are formed by stringing the letters together to add up to the number required. Like this

II = 2
XXX = 30
XII = 12
CXXIII = 123

The Rules The rule is to use the biggest numeral possible at each stage, so 15 is represented by XV not VVV nor XIIIII. It follows from this rule that numerals always go from left to right in descending order. This could still lead to some very long strings. For example, using this rule 99 would be LXXXXVIIII. So at some point a new rule was invented. A smaller value letter to the left of a larger value one is subtracted. So 4 becomes IV - which is 5 minus 1 - not IIII.

There are three rules about these smaller numerals which are placed to the left of a bigger one and subtracted.

Only I, X, and C can be used in this way; V, L, and D cannot and of course M cannot because it is the biggest numeral anyway.

Only one smaller number can be placed to the left. So 19 can be depicted XIX but 18 cannot be written XIIX. XIIX would have a certain ambiguity to it as it could be construed as 11+9=20 rather than 10-2+10=18.

The subtracted number must be no less than a tenth of the value of the number it is subtracted from. So an X can be placed to the left of a C or an L but not to the left of an M or a D. Another way of looking at this rule is that each power of ten is dealt with separately. So 49 is XL IX (without the spaces), not IL

These rules limit the usefulness of the subtraction rule in reducing the length of Roman numerals.

The strict rules about Roman numerals have been used only relatively recently. In earlier periods, although the subtractive principle was used, it seems that it was an alternative rather than compulsory and other forms such as VIIII for 9 and even IIXX for 18 are found.

30.10.2003., 15:00	#2
Rain U samoizolaciji Registracija: Jan 2003. Lokacija: Tragic Kingdom Postova: 11,866	Using Letters For Numbers The Romans depicted numbers using seven letters of the alphabet as numerals I = 1 V = 5 X = 10 L = 50 C = 100 D = 500 M = 1000 In some forms of Roman numbers, D is sometimes represented by an I followed by a backwards C, a bit like this I ) , and M is represented by a C followed by an I and a backwards C. This is hard to depict in a computer font as they do not contain a backwards C but it can be approximated using parentheses like this ( I ). The derivation of this form seems to be from the use of the deep parentheses to represent larger numbers. Thus ( I ) is 1000, ( ( I ) ) is 10,000 and ( ( ( I ) ) ) is 100,000. Forming Numbers At their simplest, numbers are formed by stringing the letters together to add up to the number required. Like this II = 2 XXX = 30 XII = 12 CXXIII = 123 The Rules The rule is to use the biggest numeral possible at each stage, so 15 is represented by XV not VVV nor XIIIII. It follows from this rule that numerals always go from left to right in descending order. This could still lead to some very long strings. For example, using this rule 99 would be LXXXXVIIII. So at some point a new rule was invented. A smaller value letter to the left of a larger value one is subtracted. So 4 becomes IV - which is 5 minus 1 - not IIII. There are three rules about these smaller numerals which are placed to the left of a bigger one and subtracted. Only I, X, and C can be used in this way; V, L, and D cannot and of course M cannot because it is the biggest numeral anyway. Only one smaller number can be placed to the left. So 19 can be depicted XIX but 18 cannot be written XIIX. XIIX would have a certain ambiguity to it as it could be construed as 11+9=20 rather than 10-2+10=18. The subtracted number must be no less than a tenth of the value of the number it is subtracted from. So an X can be placed to the left of a C or an L but not to the left of an M or a D. Another way of looking at this rule is that each power of ten is dealt with separately. So 49 is XL IX (without the spaces), not IL These rules limit the usefulness of the subtraction rule in reducing the length of Roman numerals. The strict rules about Roman numerals have been used only relatively recently. In earlier periods, although the subtractive principle was used, it seems that it was an alternative rather than compulsory and other forms such as VIIII for 9 and even IIXX for 18 are found.