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The system stores programs and data as named files. When they are
stored on DECtape or disk, files are identified by a file
specification. The file specification includes the following
1. A device name or file structure name
2. A file name
3. A file name extension
4. An ordered list of directory names
5. An access protection code
The file specification is necessary to identify a disk file. If you
issue a file specification for devices other than DECtape or disk, the
monitor ignores them. File specifications are used to choose a file
from a directory, a set of files belonging to a specific user.
DECtapes and disks are the only directory-oriented devices. Items 4
and 5 in the above list do not apply to DECtapes.
The device name can be any valid device name. Always type a colon
following the device name. An example of a device name is DSKC:. For
more help on device names, see the help file DEVNAM.
A file name is one to six alphanumeric characters. The monitor
ignores all characters past the sixth. For more help on file names,
see the help file FILNAM. An example of a device name and a file name
The file name extension is a period (.) followed by zero to three
characters. It is used to indicate the type of information in the
file. For a list of standard file name extensions, see the help file
For the most efficient use of system resources, use only standard file
name extensions, though other extensions can be valid. Most programs
recognize file names and extensions consisting only of letters and
digits. Often the term file name refers to both the file name and the
file extension. An example of a device name, file name, and file
extension is DSKC:MYFILE.TXT.
The directory name identifies the disk area where the file is stored.
This list can be a user file directory (UFD) represented by the
owner's project-programmer number, or a user file directory followed
by one or more sub-file directories (SFDs). You must enclose a
directory name in square brackets (). For more help on directory
names, see the help file DIRNAM. An example of a device name, file
name, file extension and directory name is DSKC:MYFILE.TXT[21,589].
Access Protection Code
The access protection code of a file is a 3-digit octal code
designating the users who can read or write the file. The code must
be enclosed in angle brackets (< >), and you specify it only for
output files. For a given file, users are divided into three groups:
owner of the file, users with the same project number as the owner,
and all other users. The standard protection code is <057>, allowing
users in the owner's project to read and execute the file, and
preventing access by all other users. The standard protection code
may be different at your installation. For more help on protection
codes, see the help file PCODES. An example of a full file
specification is DSKC:MYFILE.TXT[21,589]<055>.
The following information is necessary when you refer to a file:
o The file name.
o The device name, if the file is not on disk and not in your
default search list.
o The directory name, if the file is not in your directory.
The following information is optional in a file specification:
o The file name extension.
o The device name, if the file is on a file structure in your
o The directory name, if the file is in your directory.
o The protection code (if an output file).
File name and file name extension:
Physical device name and file name:
Generic device name, file name, file name extension and directory
A complete file specification: device name, file name, file name
extension, directory name, and protection code: