Installation guide

• Increased file system sizes
The following sections describe these DIGITAL UNIX features in more
detail.
1.1.1 OSF/1 Kernel
The OSF/1 kernel is based on the Mach kernel developed at
Carnegie-Mellon University. This kernel consists of a compact, extensible
system kernel designed to support distributed and parallel computing
services for single and multiprocessor systems. The OSF/1 kernel provides
the basic operating system services, including virtual memory management
and interprocess communications.
Additional code implements UNIX services as extensions to the kernel.
These extensions to the kernel are designed as kernel subsystems. File
systems, network protocol families and pseudodevice drivers, and
STREAMS drivers are some of the supported subsystems. Each subsystem
is configured into the kernel by an existing kernel-supported framework,
which provides the mechanism for registering the driver entry routines.
For example, the operating system supports the virtual file system
framework, the network framework, the device switch framework, the
interrupt dispatch framework, and the STREAMS framework.
1.1.2 Real-Time Kernel
The DIGITAL UNIX real-time kernel and environment provides you with
the capability of developing and running portable applications in a POSIX
environment. POSIX 1003.4 Draft 11 is a set of functions and calls that can
be used in the design and creation of real-time applications.
The DIGITAL UNIX real-time environment offers the following POSIX
features:
• Process synchronization. Processes can be synchronized by using the
following methods:
– Real-time clocks and timers
– Priority scheduling
– Semaphores
• Shared memory
• Process memory locking
• Asynchronous I/O
For more information on real-time programming, see the Guide to Realtime
Programming.
1–2 Introduction to Migrating from ULTRIX to DIGITAL UNIX Systems