AEGIS OPERATING SYSTEM                                                       



Apollo Computer's AEGIS operating system provides an integrated computing
environment designed to enhance technical professionals' individual and
teamwork productivities.  AEGIS combines virtual memory management with
efficient access to the DOMAIN system's high-resolution graphic displays
and high-performance local-area network.  It offers a powerful, highly
available, multiuser system environment for applications that include 
computer-aided software engineering, aritifical intelligence research,
electronic publishing, and financial modeling.

AEGIS operates across the DOMAIN network so that the user community has
easy access to information located anywhere, at a rate comparable to that
of locally attached disk access.  AEGIS gives each DOMAIN user the perform-
ance of a dedicated supermini-class processor while retaining the resource
sharing and teamwork advantages of centralized system administration.

- Shell command line interpreter for application control: an interactive
  programming language whose "verbs" are user and utility programs
- Support for a variety of programming languages and data management
  techniques

The AEGIS virtual memory operating system allows DOMAIN users to dispense
with small address spaces or clumsy overlay procedures.  Virtual memory
allows user programs to execute even though they may exceed in size the 
amount of physical memory available within the computer.  This improves
software development and maintenance by freeing users from unnecessary
complexity.  Virtual memory capability also means that significant 
applications software systems are easily transported from conventional
mainframe computers to the DOMAIN system.

AEGIS is based on "demand paging" of programs and data.  Demand paging is
a technique for transferring small units of data (pages) back and forth
between disks and processor main memory only as needed, and without user
intervention.  Paging on a demand basis offers better system performance
and responsiveness than other memory management schemes.

Demand paging's advantages operate network-wide under AEGIS. Conventional
mainframe computer systems confine demand paging's scope to a single central
processor and attached disks.  In contrast, AEGIS extends demand paging
across the entire DOMAIN local-area network.  This provides users easy
access to information located anywhere in the network, at a rate comparable
to that of locally attached disk access.  Such responsiveness also makes it
practical to support diskless DOMAIN Computational Nodes by sharing disk
resources located elsewhere in the network.


The DOMAIN system achieves network-level compatibility by supporting all
Computational and Server Nodes with same operating system.  Network-level
compatibility ensures that programs written and stored anywhere in a network
may be directly executed on any Node connected to that network - without
recompiliation, rebinding, or file copying.  An extension beyond the
processor-level compatibility offered by conventional timesharing systems,
network-level compatibility means that new Nodes become part of an existing
DOMAIN system by simply plugging them into the network.


AEGIS provides a rich complement of system services to the DOMAIN user:

- Streams I/O that is independent of file, device, or process type.
- Map/unmap calls let user programs directly access files that are not
  record-structured.
- Mailbox facility for network-wide interprocess communication, particularly
  with remote server processes.
- Eventcount management for multiprocess synchronization.
- Display Manager services to manipulate graphic "pads" and "frames".