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 runtime 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)