# ftoi(3) [ultrix man page]

```ftoi(3) 						     Library Functions Manual							   ftoi(3)

Name
ftoi, itof, dtoi, itod, gtoi, itog - convert floating values between VAX and IEEE format

Syntax
int ftoi(value)
float *value;

int itof(value)
float *value;

int dtoi(value)
double *value;

int itod(value)
double *value;

int gtoi(value)
double *value;

int itog(value)
double *value;

Description
The following C library functions convert floating values between VAX and IEEE formats.

The  function  converts the specified VAX ffloat number to IEEE single-precision format.  It returns zero if successful and nonzero without
performing the conversion if not successful (for example, underflow).

The function converts the specified IEEE single-precision number to VAX ffloat format.  It returns zero if successful and  nonzero  without
performing the conversion if not successful (for example, overflow).

The  function  converts the specified VAX dfloat number to IEEE double-precision format.  It returns zero if successful and nonzero without
performing the conversion if not successful (for example, underflow).

The function converts the specified IEEE double-precision number to VAX dfloat format.  It returns zero if successful and  nonzero  without
performing the conversion if not successful (for example, underflow or overflow).

The  function  converts the specified VAX gfloat number to IEEE double-precision format.  It returns zero if successful and nonzero without
performing the conversion if not successful (for example, underflow).

The function converts the specified IEEE double-precision number to VAX gfloat format.  It returns zero if successful and  nonzero  without
performing the conversion if not successful (for example, underflow).

ftoi(3)```

## Check Out this Related Man Page

```IEEE(3M)																  IEEE(3M)

NAME
copysign, drem, finite, logb, scalb - copysign, remainder, exponent manipulations

SYNOPSIS
#include <math.h>

double copysign(x,y)
double x,y;

double drem(x,y)
double x,y;

int finite(x)
double x;

double logb(x)
double x;

double scalb(x,n)
double x;
int n;

DESCRIPTION
These functions are required for, or recommended by the IEEE standard 754 for floating-point arithmetic.

Copysign(x,y) returns x with its sign changed to y's.

Drem(x,y) returns the remainder r := x - n*y where n is the integer nearest the exact value of x/y; moreover if |n-x/y|=1/2 then n is even.
Consequently the remainder is computed exactly and |r| <= |y|/2.  But drem(x,0) is exceptional; see below under DIAGNOSTICS.

Finite(x) = 1 just when -infinity < x < +infinity,
= 0 otherwise (when |x| = infinity or x is NaN or
x is the VAX's reserved operand.)

Logb(x) returns x's exponent n, a signed integer converted to double-precision floating-point and so chosen that 1 <= |x|/2**n < 2 unless x
= 0 or (only on machines that conform to IEEE 754) |x| = infinity or x lies between 0 and the Underflow Threshold; see below under "BUGS".

Scalb(x,n) = x*(2**n) computed, for integer n, without first computing 2**n.

DIAGNOSTICS
IEEE  754 defines drem(x,0) and drem(infinity,y) to be invalid operations that produce a NaN.  On a VAX, drem(x,0) returns the reserved op-
erand.  No infinity exists on a VAX.

IEEE 754 defines logb(+-infinity) = +infinity and logb(0) = -infinity, requires the latter to  signal  Division-by-Zero.   But  on  a  VAX,
logb(0)	= 1.0 - 2.0**31 = -2,147,483,647.0.  And if the correct value of scalb(x,n) would overflow on a VAX, it returns the reserved oper-
and and sets errno to ERANGE.

floor(3M), math(3M), infnan(3M)

AUTHOR
Kwok-Choi Ng

BUGS
Should drem(x,0) and logb(0) on a VAX signal invalidity by setting errno = EDOM?  Should  logb(0) return  -1.7e38?

IEEE 754 currently specifies that logb(denormalized no.) = logb(tiniest normalized no. > 0) but the consensus has changed to the specifica-
tion in the new proposed IEEE standard p854, namely that logb(x) satisfy
1 <= scalb(|x|,-logb(x)) < Radix	 ... = 2 for IEEE 754
for  every  x  except 0, infinity and NaN.  Almost every program that assumes 754's specification will work correctly if logb follows 854's