The 22nd General Conference on Weights and Measures[27] declared in 2003, “The symbol for the decimal marker shall be either the point on the line or the comma on the line.” It further reaffirmed,[27]
Numbers may be divided in groups of three in order to facilitate reading; neither dots nor commas are ever inserted in the spaces between groups
That is, “1 000 000 000” is preferred over “1,000,000,000” or “1.000.000.000”. This use has therefore been recommended by technical organizations, such as the United States’s National Institute of Standards and Technology.[28]
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