Roman numerals are typed on a standard keyboard by holding down the Shift key while inputting the corresponding lowercase version of a Roman numeral. The Caps Lock may be activated in favor of holding down the Shift key. An example of typing a Roman numeral on a keyboard is holding down the Shift key while typing the lowercase letter "m" to produce the Roman numeral "M."
Roman numerals are based on seven symbols: I, V, X, L, C, D and M. Each of these symbols corresponds to a specific numerical value. I, V, X, L, C, D and M represent the numbers one, five, 10, 50, 100, 500 and 1,000 respectively. The combination of these key symbols is the basis for the formulation of all other values in the numeric system.
The value of combined symbols is derived through addition. For example, III is three ones, which is equal to three, and XIII is a 10 and three ones, which is equal to 13. There is no representation for zero in the Roman numeral system. For example, 208 is CCVIII, using the symbols for two 100s, a five and three ones.
Symbols are placed from left to right in order of value, starting with the largest. However, in a few specific cases, to avoid four characters being repeated in succession, these can be reduced using subtractive notation.