One of Excel's strengths is its ability to let the user define calculations, or algorithms, for data analysis and manipulation. These algorithms may be extremely simple, such as adding two numbers, or they can be very complex with multiple inputs and outputs. With TurboExcel installed, a single button-click converts an Excel algorithm into a compiled C++ function in a DLL. This is what TurboExcel does, nothing more and nothing less. So what's the big deal?

Well, let's think about it. First off, the compiled DLL is available as an Excel add-in. The next time you need the same algorithm, you do not have to recreate it with Excel formulas and functions. This also lets you distribute worksheets that use the algorithm while keeping its implementation details secret — something that can be very useful at times. An added benefit is that a compiled add-in executes a lot faster than native Excel formulas, and no one likes to wait for a complex workbook to recalculate.

Second, the DLL is callable from any programming language that can use standard Windows DLLs, and that's pretty much every language in existence. Your algorithm is not limited to use in Excel worksheets but can be incorporated into other programs. In fact, some developers use TurboExcel primarily as a C++ prototyping and code generation tool.

The TurboExcel installation adds two new toolbar buttons to Excel. One of them brings up the configuration dialog box, in which you specify the input cells for the function as well as the data types of the inputs. You also specify the output cell and data type. The output of the TurboExcel function can be a single value or an array, as long as the array corresponds to a contiguous range of cells. After entering all the required configuration information, clicking the second button generates and compiles the C++ code. The output is a DLL and an XLL file that is required to use the function as an Excel add-in.