Appendix C: Glossary Of Terms

This glossary defines technical terms used in this manual. Common programming terms are not listed. These terms are defined for completeness, and knowledge of their definitions is not necessary to develop CauseWay applications.

3P

386 Protected mode file format, the file format used by CauseWay when building DOS extended executable files.

Aliasing

Allocating a selector that has the same base and limit as another selector but not usually the same type. Aliasing usually refers to creating a data selector that addresses the same memory as a code selector. Aliasing allows write access to variables within a code segment as long as the cs: instruction override is not used. While aliasing isn't a particularly good term for this operation because the new selector doesn't track changes to the original selector, it is the term most commonly used by developers.

API

Application Program Interface is the means by which an application communicates with the underlying operating system or environment. With CauseWay, the API is handled through INT 31h calls with the appropriate register setup.

Call-back

A mechanism which allows real mode code to switch the CPU to protected mode operation and continue execution. Call-backs are used by CauseWay to re-signal real mode hardware interrupts in protected mode.

CauseWay Application

Any program linked with the CauseWay linker when the /ex option is not used.

Descriptor

An eight-byte block of memory that describes the base address, limit, and type of a segment. In protected mode operation, each segment always has one associated descriptor.

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