Are there other important "Buzz-Words"?

· | GUID: This is a "Globally Unique Identifier", a very large number which is used to uniquely identify every interface, every class, and every COM application or library which exists anywhere in the world. GUID's identify the specific components, wherever and whenever they may be used. A GUID is a 16-byte (128-bit) value, which could be represented as an integral value or a string. This 128-bit item is large enough to represent all the possible values, anywhere in the world. The PowerBASIC GUID$() function (or a hot-key in the PowerBASIC IDE) can generate a random GUID which is statistically guaranteed to be unique from any other generated GUID. Each of these identifying GUID's may be assigned by the programmer, or they will be randomly assigned by the PowerBASIC compiler. When a GUID is written in text, it takes the form: {00CC0098-0000-0000-0000-0000000000FF}.

· | DIRECT INTERFACE: This is the most efficient form of interface. When you call a particular METHOD or PROPERTY, the compiler simply performs an indirect jump to the correct entry point listed in the virtual function table (VFT or VTBL). This is just as fast as calling a standard Sub or Function, and is the default access method used by PowerBASIC.

· | DISPATCH INTERFACE: This is a slow form of interface, originally introduced as a part of Microsoft Visual Basic. When you use DISPATCH, the compiler actually passes the name of the METHOD you wish to execute as a text string. The parameters can also be passed in the same way. The object must then look up the names, and decide which METHOD to execute, and which parameters to use, based upon the text strings provided. This is a very slow process. Many scripting languages still use DISPATCH as their sole method of operation, so continued support is necessary.

· | DUAL INTERFACE: This is a combination of a Direct Interface and a Dispatch Interface. This most flexible form allows either option to be used, depending upon how the calling application is implemented.

· | AUTOMATION: This is a special calling convention, defined by MS later in the evolution of COM and objects. An Automation object is simply one which adheres to the rules for Automation COM Objects. It may offer just a direct interface, just a Dispatch interface, or both of them (DUAL). It should be noted that some programmers use the word AUTOMATION to mean DISPATCH. Even though that's not correct, you should keep the possibility in mind whenever you encounter the term. Automation Methods must use parameters, return values, and assignment variables which are AUTOMATION compatible: BYTE, WORD, DWORD, INTEGER, LONG, QUAD, SINGLE, DOUBLE, CURRENCY, OBJECT, STRING, WSTRING, and VARIANT. A User Defined Type used as a return value or parameter will be converted to a BYVAL DWORD. All Automation Methods return a hidden result code which is called the hResult. This is not really a handle, as the name suggests, but a result code to report the success or failure of a call to a METHOD or PROPERTY.

· | IUNKNOWN: This is the name of a special interface which is the basis for every object. It has three methods, which are always defined as the first three methods in every interface. These 3 methods are used by compilers (PowerBASIC or others) to look up other interfaces on the object, and to keep track of usage of this object. While IUNKNOWN is mandatory for every object, you won't ever need to reference it directly. PowerBASIC handles all those messy details automatically.

· | OBJECT REFERENCE: This is a reference (a pointer) to an object, which is the only way objects are used. In PowerBASIC, an object variable initially contains NOTHING. When you create an object, or duplicate one, a reference to that object is placed in an object variable by the compiler. That is, a pointer to the object is automatically inserted in the object variable. It is now considered to contain an OBJECT REFERENCE until such time as the reference is deleted or set to NOTHING.

· | COMPONENT: An object that encapsulates code and data, providing a set of publicly available services.

· | MONIKER: An object that implements the IMoniker interface. A moniker acts as a name that uniquely identifies a COM object. In the same way that a path identifies a file in the file system, a moniker identifies a COM object in the directory namespace.

See Also

What is an object, anyway?

What are the parts of an object?

What does a Class look like?

What is a Base Class?