I/O statements that do not refer to a specific file or I/O device read from standard input and write to standard output. Standard input is the keyboard, and standard output is the screen (console). To perform input and output on a physical device other than the keyboard or screen, you specify the device name as the filename to be read from or written to.
Some physical device names are determined by the host operating system; others are recognized by Visual Fortran. Extensions on most device names are ignored.
Filenames for Device I/O
| Device | Description |
|---|---|
| CON | Console (standard output) |
| PRN | Printer |
| COM1 | Serial port #1 |
| COM2 | Serial port #2 |
| COM3 | Serial port #3 |
| COM4 | Serial port #4 |
| LPT1 | Parallel Port #1 |
| LPT2 | Parallel Port #2 |
| LPT3 | Parallel Port #3 |
| LPT4 | Parallel Port #4 |
| NUL | NULL device. Discards all output; contains no input |
| AUX | Serial port #1 |
| LINE 1 | Serial port #1 |
| USER 1 | Standard output |
| ERR 1 | Standard error |
| CONOUT$ | Standard output |
| CONIN$ | Standard input |
1 If you use one of these names with an extension—for example, LINE.TXT—Fortran will write to a file rather than to the device.
Examples of opening physical devices as units are:
OPEN (UNIT = 4, FILE = 'PRN')
OPEN (UNIT = 7, FILE = 'LPT2', ERR = 100)