Converts its argument to a null-terminated string of ASCII digits
    and returns the address of the string.

    Format

      #include  <stdlib.h>

      char *gcvt  (double value, int ndigit, char *buffer);

1 - Function Variants

    The gcvt function has variants named _gcvt32 and _gcvt64 for use
    with 32-bit and 64-bit pointer sizes, respectively.

2 - Arguments

 value

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

 ndigit

    The number of ASCII digits to use in the converted string. If
    ndigit is less than 6, the value of 6 is used.

 buffer

    A storage location to hold the converted string.

3 - Description

    The gcvt function places the converted string in a buffer and
    returns the address of the buffer. If possible, gcvt produces
    ndigit significant digits in F-format, or if not possible, in
    E-format. Trailing zeros are suppressed.

    The ecvt, fcvt, and gcvt functions represent the following
    special values specified in the IEEE Standard for floating-point
    arithmetic:

    Value         Representation

    Quiet NaN     NaNQ
    Signalling    NaNS
    NaN
    +Infinity     Infinity
    -Infinity     -Infinity

    The sign associated with each of these values is stored into the
    sign argument. In IEEE floating-point representation, a value
    of 0 (zero) can be positive or negative, as set by the sign
    argument.

    See also fcvt and ecvt.

4 - Return Value

    x                  The address of the buffer.