Why Decimal Point and Decimal Comma

Originally published at: Why Decimal Point and Decimal Comma | Boing Boing


Totally tedious tiny terror of this issue, some bright bulb waaay back in the 1990s decided to use CSV format as part of a joint scientific data-pool of mostly numerical data. That is, CSV : comma separated values. And with some of the gigabytes of numeric data having decimal points arriving as decimal commas and even getting mixed into the same files …well it was “more fun” than our worst dreams imagined. Eventually we went to TSV: tab separated data fields and that was a great improvement.


Interested to see Canada designated as (presumably) mixed use. Is that really all across the country or would there be strong regional differences, with large parts of the country using decimal point predominantly and the more French-speaking areas showing decimal comma or mixed use?


Leibniz had a point, if you ask me.


In the spirit of “why not both”, I have taken to using a semicolon.

Thus pi = 3;14159…


Depending upon where one is from

Yeah, it’s a regional distinction. It’s like the way North Americans use “watershed” to mean a drainage basin, while English speakers in the rest of the world use it to mean drainage divide. Except it also means drainage divide in North America when it’s used metaphorically.

As an American, I found that word so confusing until I found out that its meaning had been changed in our part of the world. That was a watershed moment.


You Got Me GIF by HULU


Next up, date formats and how it all went wrong.


Doesn’t even mention the common use of a comma to group digits by 1000s. Eg. $987,488 is nearly a million dollars, and not nearly a thousand. And then there is the confusion as to whether i is the square root of -1, current, or the unit vector in the x direction.


When we faced down the problem of the arrival of the millennium (remember Y2K?), I switched over completely to the only unambiguous format YYYY-MM-DD, which is also (handily) the only one that sorts numerically.

This is already an ISO standard so get with it, the rest of you holdouts!


Particularly annoying as ASCII already had characters specifically reserved for separating data records and fields within those records:

  • 30 RS (Record separator)
  • 31 US (Unit separator)

Is noon PM and midnight AM?

(Short answer: no.)


The linked Wikipedia article notes English-speaking Canada officially uses the English version of SI notation:
1 234 567.89

and unofficially uses:

while French-speaking Canada uses the French version:
1 234 567,89

The one that really confuses me is the interpunct.

Malaysia, Philippines (uncommon today), Singapore, United Kingdom (older, typically handwritten; in education)


Regional, yep, and maddening. Quebec uses the comma and everywhere else uses the period. However many folks like myself who grew up in anglophone parts of the country but went to French Immersion schools used all commas in our studies because it’s The French Way. Then gradually (or suddenly) we unlearned it upon adulthood and/or switching to regular bilingual schools. Whichever came first. But even in French Immersion school, we had to use periods in English class (the only class actually in English) because we were writing English, but everything else (math, science, etc) was commas because the context was French.

Furthermore, as @ghostbloke notes, proper Canadian English uses spaces as thousands separators (and boy would your teachers chew you out for doing that wrong) but sometimes people use commas in casual writing because of the constant and unrelenting influence of American culture.

The spaces as thousands separators is actually pretty important here, because if you use commas, then a number like 58,042 becomes extremely ambiguous depending on which Canadian might be reading it. Such ambiguity could even be dangerous in certain settings, such as engineering.


The • is still used for multiplication in Germany, btw. At least that’s how I learned it in school.

2 • 3,5 = 7


Yep, we use it in Canada as well. I never saw the “x” used for it unless reading something American, even through University. The dot was considered more correct and more elegant for the purpose. Same with / in place of ÷. We never ever used the latter, as it seems Americans often do.

Of course the dot is really just there to disambiguate situations where simple adjacency of terms would be confusing. 3x is fine, but 35 for three times five would be unclear, so 3 • 5 is used. That rarely came up after early grade school, when multiplication between rational constants was the main focus.


I feel that, life gets hectic when dirty data go BRRRR.

You bet your bollocks to a barn dance I remember Y2K, my first job out of art school was for a company that did Eclipse implementations on mainframes because the federal gov looked at code as an asset that should be taxed differently when in use, but because of Y2K, no one had time or money for Eclipse in their budget, so we went belly up less than a year after I started working there.

On the date schema, I 100% co-sign on this and even have a meme for it:

So, now you’ve got me wondering, do the multiplication & division symbols on your calculator look like this? :thinking:


We had a completely different education. In Ontario we always used x for multiply and ÷ for divide, until we learned programming, when we used * (asterisk) and /.

As @shichae points out, calculators (all the ones I’ve seen) use +, -, x, and ÷ for the basic arithmetic symbols.


Had some friends who moved to Europe suffer an off-by-1000x error in transferring their US bank balance because of this nonsense. That was zero fun.


I prefer the Oxford decimal point.