Accessing Files Programmer's Guide (32650-90885)

72 Chapter3
Specifying a File Designation
MPE/iX File Designators
MPE/iX File Designators
The file system recognizes two general classes of files:
• user-defined files, which you or other users define, create, and make available for your
own purposes
• system-defined files, which the file system defines and makes available to all users to
indicate standard input/output devices
These files are distinguished by the file names and other descriptors (such as group or
account names) that reference them, as discussed below. You may use both the file name
and descriptors, in combination, as either formal designators within your programs or as
actual designators that identify the file to the system. Generally, however, most
programmers use only arbitrary names as formal designators, and then equate them to
appropriate actual file designators at run time. In such cases, the formal designators (user
file names) contain from one to eight alphanumeric characters, beginning with a letter; the
actual designators include a user or system file name, optionally followed by a group name,
account name, and/or security lockword, all separated by appropriate delimiters. This
technique facilitates maximum flexibility with respect to file references.