OLE Automation Sample


SUMMARY
=======

The DispCalc sample is a simple accumulator-based calculator. Its user 
interface consists of buttons for the numbers (0-9), the operators 
(+, -, *, /), and some other necessary buttons (C for Clear, = for 
evaluation). Its programmability interface consists of one object, which is 
described below.

The ProgID for DispCalc's only object is "DispCalc.Application". An instance
of this object can be created by executing the following lines of code in 
Visual Basic or DispTest:

    Sub Foo
        Dim MyCalculator as Object	
        Set MyCalculator = CreateObject("DispCalc.Application")
        . . .
    End Sub

MORE INFORMATION
================

Program Structure
-----------------

DispCalc uses INTERFACEDATA and CreateStdDispatch to implement the 
IDispatch interface.

Properties for the Object
-------------------------

Name     Type     Description

Value    VT_I4    Same as the value for the accumulator.
Accum    VT_I4    The value that is in the accumulator of the calculator.
Opnd     VT_I4    The operand. This is the number currently being entered.
Op       VT_I2    The operator that is currently being used. This is an 
                  enumeration:
                      const OP_NONE = 0
                      const OP_PLUS = 1 
                      const OP_MINUS = 2
                      const OP_MULT = 3

Methods Defined on the Object
-----------------------------

Name                               Description

Eval as Boolean                    If there is an operator, apply it to the
                                   accumulator and the operand, placing the
                                   result in the accumulator. The return 
                                   value indicates success or failure.
Clear                              Resets the calculator. This sets Op to
                                   OP_NONE, and both Accum and Opnd to 0.
Display                            Updates the display of the calculator.
                                   (Other operations do not do this.)
Quit                               Close the calculator.
Button (b as string) as Boolean    Press the indicated button and return
                                   success or failure. Valid string values 
                                   are:
                                       +, -, *, +
                                       0-9
                                       c, C
                                       =

                                   Note that you may also pass the numbers 
                                   0-9 and these will be converted to 
                                   strings automatically.

Shortcomings of this Sample
---------------------------

Property and method names should not be abbreviated. For example, the "Opnd" 
property should be the "Operand" property.

Because the object is the application object, it should have Name and 
Version properties, which are read-only.