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Numeral system
Numeral systems by culture  

Hindu–Arabic numerals  
Western Arabic Eastern Arabic Khmer 
Indian family Brahmi Thai 
East Asian numerals  
Chinese Suzhou Counting rods 
Japanese Korean 
Alphabetic numerals  
Abjad Armenian Cyrillic Ge'ez 
Hebrew Greek (Ionian) Āryabhaṭa 
Other systems  
Attic Babylonian Egyptian Etruscan 
Mayan Roman Urnfield 
List of numeral system topics  
Positional systems by base  
Decimal (10)  
2, 4, 8, 16, 32, 64  
1, 3, 9, 12, 20, 24, 30, 36, 60, more…  
A numeral system (or system of numeration) is a way to write numbers. Roman numerals and tally marks are examples. "11" usually means eleven, but if the numeral system is binary, then "11" means three.
A numeral is a symbol or group of symbols, or a word in a natural language that represents a number. Numerals differ from numbers just as the word "rock" differs from a real rock. The symbols "11", "eleven" and "XI" are different numerals, all representing the same number. This article tries to explain the different systems of numerals. See also number names.
Bases
There are different symbols that can be used to make numbers. In a system with base 10 (the normal decimal system), usually the symbols 0,1,2, 3, 4, 5,6, 7, 8, and 9 are used. The numbers 0 to 9 can be written as one symbol, 0 ... 9. To count past 9, symbols have to be put together. 10 can be seen as 1 in the tens' place and 0 in the ones' place, or as 1 times 10^{1} plus 0 times 10^{0}. With a base of 2, only the symbols 0 and 1 are used. 10 in base 2 notation is therefore 1 times 2^{1} plus 0 times 2^{0}. This is the same as 2, in the base 10 notation.
For bases bigger than 10, capital letters are used as symbols. For example, the hexadecimal numeral system (base 16) uses the numerical digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F.
Today, mainly bases 2, 8, 10, 12 and 16 are in use.
Most electronic calculations are done in binary (base 2), but most people do calculations in decimal (base ten).
Other websites
 History of Counting and Numeral SystemsPlainMath.Net
 Online Converter for Different Numeral Systems (Base 236, JavaScript, GPL)
 Online Converter for Decimal/Roman Numerals (JavaScript, GPL)
 Number Sense & Numeration Lessons
 Counting Systems of Papua New Guinea

