# How to use million separator on my output?

On the question Way to improve "show me this decimal number to M places, don't use scientific notation"? I learned how to automatically not use scientific notation with:

format[x_Real] := NumberForm[x, ExponentFunction -> (Null &)];
format[x_] := x;
$Post = format;  Then my numbers are outputting better than before as : 4096^2*12*3.620 724775731.20000000000  But it is missing the miliar separator as comma ,. For example, the number 724775731.20000000000 should output as 724,775,731.20000000000 so I can understand it easily. Can the output the show as 724,775,731.20000000000 instead of 724775731.20000000000? Related: • Look up the DigitBlock and NumberSeparator options. Do read the whole doc page for NumberForm[] while you're at it. – J. M.'s torpor Sep 4 '17 at 15:28 • Take a look at Preferences -> Appearance -> Numbers -> Formatting. – Szabolcs Sep 4 '17 at 15:37 ## 1 Answer Thanks to the comments, I find out how to set it automatically to  option: format[x_Real]:=NumberForm[x,ExponentFunction->(Null&),DigitBlock->3,NumberSeparator->","]; format[x_]:=x;$Post=format;


Now these:

4096^2*12*3.610
4096^320


Outputs as:

724,775,731.2
68,719,476,736.000,000,0