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### 14.2.9 Floating-Point Conversions

This section discusses the conversion specifications for floating-point
numbers: the ‘`%f`’, ‘`%e`’, ‘`%E`’, ‘`%g`’, and ‘`%G`’
conversions.

The ‘`%f`’ conversion prints its argument in fixed-point notation,
producing output of the form
[`-`

]`ddd``.`

`ddd`,
where the number of digits following the decimal point is controlled
by the precision you specify.

The ‘`%e`’ conversion prints its argument in exponential notation,
producing output of the form
[`-`

]`d``.`

`ddd``e`

[`+`

|`-`

]`dd`.
Again, the number of digits following the decimal point is controlled by
the precision. The exponent always contains at least two digits. The
‘`%E`’ conversion is similar but the exponent is marked with the letter
‘`E`’ instead of ‘`e`’.

The ‘`%g`’ and ‘`%G`’ conversions print the argument in the style
of ‘`%e`’ or ‘`%E`’ (respectively) if the exponent would be less
than -4 or greater than or equal to the precision; otherwise they use the
‘`%f`’ style. Trailing zeros are removed from the fractional portion
of the result and a decimal-point character appears only if it is
followed by a digit.

The following flags can be used to modify the behavior:

- ‘
`-`’ Left-justify the result in the field. Normally the result is right-justified.

- ‘
`+`’ Always include a plus or minus sign in the result.

- ‘
If the result doesn't start with a plus or minus sign, prefix it with a space instead. Since the ‘

`+`’ flag ensures that the result includes a sign, this flag is ignored if you supply both of them.- ‘
`#`’ Specifies that the result should always include a decimal point, even if no digits follow it. For the ‘

`%g`’ and ‘`%G`’ conversions, this also forces trailing zeros after the decimal point to be left in place where they would otherwise be removed.- ‘
`0`’ Pad the field with zeros instead of spaces; the zeros are placed after any sign. This flag is ignored if the ‘

`-`’ flag is also specified.

The precision specifies how many digits follow the decimal-point
character for the ‘`%f`’, ‘`%e`’, and ‘`%E`’ conversions. For
these conversions, the default precision is `6`

. If the precision
is explicitly `0`

, this suppresses the decimal point character
entirely. For the ‘`%g`’ and ‘`%G`’ conversions, the precision
specifies how many significant digits to print. Significant digits are
the first digit before the decimal point, and all the digits after it.
If the precision is `0`

or not specified for ‘`%g`’ or
‘`%G`’, it is treated like a value of `1`

. If the value being
printed cannot be expressed precisely in the specified number of digits,
the value is rounded to the nearest number that fits.

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