Input/Output

Fortran input and output are performed on logical units. A unit is

• a non-negative INTEGER associated with a physical device such as a disk file, the console, or a printer. The unit must be connected to a file or device in an OPEN statement, except in the case of pre-connected files.
• an asterisk, `*', indicating the standard input and standard output devices, usually the keyboard and monitor, that are preconnected.
• a CHARACTER variable corresponding to the name of an internal file.

Fortran statements are available to connect (OPEN) or disconnect (CLOSE) files and devices from input/output units; transfer data (PRINT, READ, WRITE); establish the position within a file (REWIND, BACKSPACE, ENDFILE); and inquire about a file or device or its connection (INQUIRE).

In the following sections, these topics are described:

• Preconnected Units describes the standard in, standard out and standard error units.
• Files describes file I/O concepts and the types of files supported by Fortran 95.
• Carriage Control covers the legacy aspects of controlling output using Fortran carriage control commands.
• Input/Output Editing describes the formatting of data both for input and output.