Glossary

• An application is some code (program or program fragment) that is executed or traced by one of the tools described here.

  Note that an operating system is considered an application: it is thus possible to speak distinctly of the host and target operating systems.

  The target operating system may itself be managing programs; these are considered to be a part of the OS ``application'' and are refered to as ``user-mode parts of the application''.

• Emulation is simulating a target machine using both software and a host machine that has special hardware to help speed the simulation.

  See: [Tucker 65]; referenced by [Wilkes] as the original definition.

• Fidelity From Paul A. Fishwick <fishwick@cis.ufl.edu>: ``Simulation fidelity'' is usually captured under the title ``Validation'' within the simulation literature, and within modeling literature in general. A good place to start with validation is the proceedings of the Winter Simulation Conference since the first part of the proceedings is dedicated to tutorials and introductions. Recently, Sargent had a tutorial on validation and you may find others as well.

• The host machine is the ``real machine'' where the simulation or tracing is finally run. Compare to the target machine, which is the machine that is being simulated or traced.

  Note that the host and the target may be the same machine, e.g. a V8 SPARC simulator that runs on a V8 SPARC. See also virtual host.

  There are many other terms that can and have been used for host and target. For example, [Wilkes] refers to them as the ``object machine'' and ``subject machine''.

• Static analysis, optimization, etc. is performed using the static code but no runtime data.

  Compare to dynamic or runtime operations, which may use program data and which may be interleaved with program execution.

  Note that static execution is possible, but is limited to pieces that do not depend on program data or places where data values is speculated and a ``backup'' mechanism is available where the speculation was erronious.

• The target machine is the machine that is being simulated or traced. The target machine may be old hardware (e.g. machines that no longer exist), proposed hardware (e.g. machines that do not yet exist), or machines that do currently exist, but for which it is nonetheless valuable to perform simulation or tracing. Compare to the host machine, which is the real machine that actually executes the simulation and tracing code.

  Note that the host and target may be the same machine, e.g. a V8 SPARC simulator that runs on a V8 SPARC.

  There's reportedly an IBM paper that referes to the target as the ``guest'' machine.

• The term virtual host may be used when there are several levels of simulation and tracing. For example, SoftPC can run on a SPARC and simulate an 8086; that simulated 8086 can then execute Z80MU, which rus on an 8086 and simulates a Z80. As far as Z80MU is concerned, it is running on an 8086 host; the simulated 8086 provided by SoftPC is thus a virtual host for Z80MU.

  Note that the real host and the virtual host may be the same machine. For example, Shade runs on a V8 SPARC and simulates a V8 SPARC, and so Shade can simulate a V8 SPARC that is running Shade that is simulating a V8 SPARC that is running an application.