`_fcvt`

Article
12/02/2022

Converts a floating-point number to a string. A more secure version of this function is available; see _fcvt_s.

Syntax

char *_fcvt(
   double value,
   int count,
   int *dec,
   int *sign
);

Parameters

value
Number to be converted.

count
Number of digits after the decimal point.

dec
Pointer to the stored decimal-point position.

sign
Pointer to the stored sign indicator.

Return value

_fcvt returns a pointer to the string of digits, NULL on error.

Remarks

The _fcvt function converts a floating-point number to a null-terminated character string. The value parameter is the floating-point number to be converted. _fcvt stores the digits of value as a string and appends a null character ('\0'). The count parameter specifies the number of digits to be stored after the decimal point. Excess digits are rounded off to count places. If there are fewer than count digits of precision, the string is padded with zeros.

The total number of digits returned by _fcvt won't exceed _CVTBUFSIZE.

Only digits are stored in the string. The position of the decimal point and the sign of value can be obtained from dec and sign after the call. The dec parameter points to an integer value; this integer value gives the position of the decimal point with respect to the beginning of the string. A zero or negative integer value indicates that the decimal point lies to the left of the first digit. The parameter sign points to an integer indicating the sign of value. The integer is set to 0 if value is positive and is set to a nonzero number if value is negative.

The difference between _ecvt and _fcvt is in the interpretation of the count parameter. _ecvt interprets count as the total number of digits in the output string, whereas _fcvt interprets count as the number of digits after the decimal point.

_ecvt and _fcvt use a single statically allocated buffer for the conversion. Each call to one of these routines destroys the results of the previous call.

This function validates its parameters. If dec or sign is NULL, or count is 0, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, errno is set to EINVAL, and NULL is returned.

By default, this function's global state is scoped to the application. To change this behavior, see Global state in the CRT.

Requirements

Function	Required header
`_fcvt`	<stdlib.h>

For more compatibility information, see Compatibility.

Example

// crt_fcvt.c
// compile with: /W3
// This program converts the constant
// 3.1415926535 to a string and sets the pointer
// buffer to point to that string.

#include <stdlib.h>
#include <stdio.h>

int main( void )
{
   int  decimal, sign;
   char *buffer;
   double source = 3.1415926535;

   buffer = _fcvt( source, 7, &decimal, &sign ); // C4996
   // Note: _fcvt is deprecated; consider using _fcvt_s instead
   printf( "source: %2.10f   buffer: '%s'   decimal: %d   sign: %d\n",
            source, buffer, decimal, sign );
}

source: 3.1415926535   buffer: '31415927'   decimal: 1   sign: 0