I read it originally in the documentation of the standard C library. You can certainly find the IEEE standard on this.

Strangely, your "trick" with the format does not work for me on 5.14.2: 

$ perl -wE 'printf qq[%9f\t%.0f\t%2.0f\n], ($_ + 0.5) x 3 for 0 .. 10;
+'
 0.500000       0        0
 1.500000       2        2
 2.500000       2        2
 3.500000       4        4
 4.500000       4        4
 5.500000       6        6
 6.500000       6        6
 7.500000       8        8
 8.500000       8        8
 9.500000       10      10
10.500000       10      10

[download]

In reply to Re^4: How to calculate the sum of columns to be equal to 100? by Laurent_R
in thread How to calculate the sum of columns to be equal to 100? by Anonymous Monk

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