See:
          Description

System and Options

This section contains classes describe the handling of POSIX signals, or related to the system as a whole. These classes:

• Provide a common idiom for binding POSIX signals to instances of AsyncEventHandler when POSIX signals are available on the underlying platform.
• Provide a class that contains operations and semantics that affect the entire system.
• Provide the security semantics required by the additional features in the entirety of this specification, which are additional to those required by implementations of the Java Language Specification.

The RealtimeSecurity class provides security primarily for physical memory access.

Semantics and Requirements

This list establishes the semantics and requirements that are applicable across the classes of this section.  Semantics that apply to particular classes, constructors, methods, and fields will be found in the class description and the constructor, method, and field detail sections.

1. The POSIX signal handler class is required to be available when implementations of this specification execute on an underlying platform that provides POSIX signals or any subset of signals named with the POSIX names.
2. The RealtimeSecurity class is required.
3. If applications execute the method call, System.getProperty("javax.realtime.version"), the return value will be a string of the form, "x.y.z". Where 'x' is the major version number and 'y' and 'z' are minor version numbers. These version numbers state to which version of the RTSJ the underlying implementation claims conformance. The first release of the RTSJ, dated 11/2001, is numbered as, 1.0.0. Since this property is required in only subsequent releases of the RTSJ implementations of the RTSJ which intend to conform to 1.0.0 may return the String "1.0.0" or null.

Rationale

This specification accommodates the variation in underlying system variation in a number of ways. One of the most important is the concept of optionally required classes (e.g., the POSIX signal handler class). This class provides a commonality that can be relied upon by program logic that intends to execute on implementations that themselves execute on POSIX compliant systems.

The RealtimeSystem class functions in similar capacity to java.lang.System.  Similarly, the RealtimeSecurity class functions similarly to java.lang.SecurityManager.