7.1.1.2 Logical Unit Specifier

The logical unit specifier identifies the logical unit to be accessed. The logical unit specifier takes either of the following forms:

{ [UNIT=]u }
{ [UNIT=]* }

u

Is an integer expression with a value that refers to a specific file or I/O device. On VAX processors, the integer is in the range of 0 through 119; on Alpha processors, the integer is in the range of 0 through 2**31-1.

If necessary, the value is converted to integer data type before use.

*

Specifies that the default input or output unit is to be accessed.

The keyword UNIT is optional if the logical unit specifier is the first parameter in the control list.

A logical unit number is assigned to a file, device, or Tru64 UNIX pipe in one of two ways:

• Explicitly through an OPEN statement

• Implicitly by the system

If you use READ to implicitly open a file, the file is opened as STATUS='OLD'. If you use WRITE to implicitly open a file, the file is opened as follows:

• On OpenVMS systems: STATUS='NEW'

• On Tru64 UNIX systems: STATUS='UNKNOWN'

For More Information:

• On the OPEN statement: on OpenVMS systems, see Section 9.6; on Tru64 UNIX systems, see Section 10.6.

• On implicit logical assignments, see your user manual.