I have found a reference which has some rules for constructing
roman numerals.
Firstly, four of a given numeral is okay, but five or more is
not. This allows VIIII to be valid.
You must use the largest numeral at a given stage, so for 15,
you don't write VVV, you write XV.
Numerals of a lower value, when written in front of a higher
valued numeral subtract their value from the higher valued
numeral.
Further rules for the subtraction:
o Only I X and C can be used in this way. V, L and D
cannot (nor can M)
o Only one smaller numeral can be written first. So
XIIX is not valid for 18.
o The lower numeral must be no less than a tenth of the
value of the higher numeral.
o It specifically states that each power of ten is handled
separately, and uses the example that 49 is NOT IL, it is
correctly XLIX.
These are the rules I have used in my routine...
Megan Gentry
Former RT-11 Developer
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Received on Wed Apr 21 1999 - 13:10:08 BST