value

    An object of type double that is converted to a null-terminated
    string of ASCII digits.

 ndigits

    The number of ASCII digits to be used in the converted string.

 decpt

    The position of the decimal point relative to the first character
    in the returned string. A negative int value means that the
    decimal point is decpt number of spaces to the left of the
    returned digits (the spaces being filled with zeros). A 0 value
    means that the decimal point is immediately to the left of the
    first digit in the returned string.

 sign

    An integer value that indicates whether the value argument is
    positive or negative. If value is negative, the function places
    a nonzero value at the address specified by sign. Otherwise, the
    function assigns 0 to the address specified by sign.