OPEN: CONVERT Specifier

Intel® Fortran Compiler Classic and Intel® Fortran Compiler Developer Guide and Reference

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ID 767251

Date 7/13/2023

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OPEN: CONVERT Specifier

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)

Parent topic: OPEN Statement Specifiers

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OPEN: CONVERT Specifier

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