Almost every kind of organization in our modern society is
concerned in some way with information. Corporations keep track
of their business dealings, political groups keep lists of potential
voters, and families remember whose turn it is to do the dishes.
When an organization needs to deal with large amounts of information
in an efficient, dependable manner, a computer can be an indispensable
aid. This manual describes the MPE/iX file system that is responsible
for handling information in the 900 Series of the HP 3000 Family.
Figure 1-1 "File System Interface" shows the
relationships among your
program, the MPE/iX file system, the MPE/iX I/O System, and the
actual hardware of the system. Notice that the MPE/iX file system
serves as the interface between you and the rest of the system.
Figure 1-1 File System Interface
The file system is the part of the MPE/iX operating system
that manages information being transferred or stored with peripheral
devices. It handles various input/output operations, such as the
passing of information to and from user processes, compilers, and data
management subsystems. Conceptually, these data transfers are very
simple: information is arranged into data elements within a record;
this record is then input, processed, and output as a single unit.
Logically related records are grouped into sets known to the file system as
files, which may be kept in any storage medium or sent to any input/output
peripheral (as illustrated in Figure 1-2
"Records/Files Relationship" below).
Figure 1-2 Records/Files Relationship
Since all input/output operations are done through the mechanism
of files, you may access very different devices in a standard, consistent
way. It does not make much difference to you whether you read your
file from a disk or from a magnetic tape, because the file system permits
you to treat all files in the same way. This property of the file
system gives your program device independence; the name and characteristics
assigned to a file when it is defined in a program do not restrict
that file to residing on the same device every time the program
is run. You, the user, need only reference the file by the file
name assigned to it when it was created, and the file system determines
the device or disk address where the file is stored and access the
file for you. (Of course, you should be aware of the properties
of the device you're using. For example, the MPE/iX file system
permits you to read a file from a line printer.)