The CONVERT
specifier indicates a nonnative numeric format for unformatted data. It takes
the following form:
CONVERT =
fm
fm |
Is a
scalar default character expression that evaluates to one of the following
values:
'LITTLE_ENDIAN'1
|
Little endian integer data
2 and IEEE*
floating-point data.
3
|
'BIG_ENDIAN'1
|
Big endian integer data
2 and IEEE
floating-point data.
3
|
'CRAY'
|
Big endian integer data
2 and CRAY*
floating-point data of size REAL(8) or COMPLEX(8).
|
'FDX'
|
Little endian integer data
2 and VAX*
processor floating-point data of format F_floating for REAL(4) or COMPLEX(4),
D_floating for size REAL(8) or COMPLEX(8), and IEEE binary128 for REAL(16) or
COMPLEX(16).
|
'FGX'
|
Little endian integer data
2 and VAX
processor floating-point data of format F_floating for REAL(4) or COMPLEX(4),
G_floating for size REAL(8) or COMPLEX(8), and IEEE binary128 for REAL(16) or
COMPLEX(16).
|
'IBM'
|
Big endian integer data
2 and IBM*
System\370 floating-point data of size REAL(4) or COMPLEX(4) (IBM short 4), and
size REAL(8) or COMPLEX(8) (IBM long 8).
|
'VAXD'
|
Little endian integer data
2 and VAX
processor floating-point data of format F_floating for size REAL(4) or
COMPLEX(4), D_floating for size REAL(8) or COMPLEX(8), and H_floating for
REAL(16) or COMPLEX(16).
|
'VAXG'
|
Little endian integer data
2 and VAX
processor floating-point data of format F_floating for size REAL(4) or
COMPLEX(4), G_floating for size REAL(8) or COMPLEX(8), and H_floating for
REAL(16) or COMPLEX(16).
|
'NATIVE'
|
No data conversion. This is the default.
|
1
INTEGER(1) data is the same for little endian and big endian.
2
Of the appropriate size: INTEGER(1), INTEGER(2), INTEGER(4), or INTEGER(8)
3
Of the appropriate size and type: REAL(4), REAL(8), REAL(16), COMPLEX(4),
COMPLEX(8), or COMPLEX(16)
|
|
You can use
CONVERT to specify multiple formats in a single program, usually one format for
each specified unit number.
When reading a
nonnative format, the nonnative format on disk is converted to native format in
memory. If a converted nonnative value is outside the range of the native data
type, a run-time message appears.
There are other
ways to specify numeric format for unformatted files: you can specify an
environment variable, compiler option convert, or
OPTIONS/CONVERT. The
following shows the order of precedence:
Method Used
|
Precedence
|
|---|
An
environment variable
|
Highest
|
OPEN
(CONVERT=)
|
.
|
OPTIONS/CONVERT
|
.
|
The
convert compiler option
|
Lowest
|
Compiler option
convert and OPTIONS/CONVERT affect all unit numbers used by the program, while
environment variables and
OPEN (CONVERT=) affect
specific unit numbers.
The following
example shows how to code the OPEN statement to read unformatted CRAY* numeric
data from unit 15, which might be processed and possibly written in native
little endian format to unit 20:
OPEN (CONVERT='CRAY', FILE='graph3.dat', FORM='UNFORMATTED',
1 UNIT=15)
...
OPEN (FILE='graph3_native.dat', FORM='UNFORMATTED', UNIT=20)