Reads numeric data that is stored in real binary
(floating-point) notation.

Category: | Numeric |

Default: | 4 |

Ranges: | 2 to 8, 0 to 10 |

UNIX specifics: | floating-point representation; supports single-precision numbers only for those applications that truncate numeric data |

See: | RBw.d Informat in SAS Formats and Informats: Reference |

The RBw.d informat
reads numeric data that is stored in real binary (floating-point)
notation. SAS stores all numeric values in floating-point.

It is usually impossible
to type floating-point binary data directly from a console, but many
programs write floating-point binary data. Use caution if you are
using the RBw.d informat to
read floating-point data created by programs other than SAS because
the RBw.d informat is designed
to read only double-precision data.

All UNIX systems that
are currently supported by SAS use the IEEE standard for floating-point
representation. This representation supports both single-precision
and double-precision floating-point numbers. Double-precision representation
has more bytes of precision, and the data within the representation
is interpreted differently. For example, for single-precision, the
value of 1 in hexadecimal representation is

`3F800000`

.
For double-precision, the hexadecimal representation of 1 is `3FF0000000000000`

.
The RBw.d informat
is designed to read only double-precision data. It supports widths
less than 8 only for applications that truncate numeric data for space-saving
purposes. RB4. does not expect
a single-precision floating-point number; it expects a double-precision
number truncated to four bytes. Using the example of 1 above, RB4.
expects

`3FF00000`

to be the hexadecimal representation
of the four bytes of data to be interpreted as 1. If given `3F800000`

,
the single-precision value of 1, a different number results.
External programs such
as those programs that are written in the C and Fortran languages
can produce only single-precision or double-precision floating-point
numbers. No length other than four or eight bytes is allowed. RBw.d allows
a length of 3 through 8, depending on the storage that you need to
save.

The FLOAT4. informat
has been created to read a single-precision floating-point number.
If you read 3F800000 with FLOAT4., the result is a value of 1.

To read data created
by a C or Fortran program, you need to decide on the proper informat
to use. If the floating-point numbers require an eight-byte width,
you should use the RB8. informat. If the floating point numbers require
a four-byte width, you should use FLOAT4.

Consider the following
C example:

#include <stdio.h> main() { FILE *fp; float x[3]; fp = fopen("test.dat","wb"); x[0] = 1; x[1] = 2; x[2] = 3; fwrite((char *)x,sizeof(float),3,fp); fclose(fp); }The file test.dat contains

`3f8000004000000040400000`

in
hexadecimal representation.
The following statements
read test.dat correctly:

data _null_; infile 'test.dat'; input (x y z) (float4.); run;

Also available is the
IEEEw.d informat, which reads
IEEE floating-point data. On UNIX systems, IEEE8. is equivalent to
RB8., and IEEE4. is equivalent to FLOAT4. IEEEw.d can
be used on any platform, as long as the original IEEE binary data
originated on a platform that uses the IEEE representation.

For more information,
see Reading and Writing Binary Data in UNIX Environments.