value

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

 ndigits

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

 decpt

    The position of the decimal point relative to the first character
    in the returned string. The returned string does not contain the
    actual decimal point. A negative int value means that the decimal
    point is decpt number of spaces to the left of the returned
    digits (the spaces are 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 fcvt function
    places a nonzero value at the address specified by sign.
    Otherwise, the functions assign 0 to the address specified by
    sign.