February 28, 2021
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VB6 Programmer's Introduction to COM

  • By James Limm
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To reinforce the point, let's take a look at a problem for which COM could provide a viable solution. Phil is the project leader of a new application for his company Frogs & Turtles, a retail chain that sells garden plants and accessories. Currently, they are using proprietary software that runs at each retail chain and on each order taker's system at the catalog telephone center. This application batches all orders into a text file and uses a modem to transfer the orders for the next day overnight, where they are then updated to the main database. If there are orders for something that's not in stock, a fax is sent to the representative that took the order the next morning. Unfortunately, there are some problems with the current system.

The first problem is that the software is proprietary, so Phil and his group of developers are unable to add any features to it or debug any of the problems they have found without having the code base. Second, customer satisfaction is low due to inventory control problems. Because they have grown so quickly, their technology has not kept up with their demand: they cannot tell what their inventory levels are until the nightly batches are through. In addition, when a customer puts in an order late in the day, they will not know until the representative calls the next morning that their order is on backorder. Third, when orders are filled out wrongly and entered into the system, it can mess up reporting, wreck the order, or even crash the system the order took place on.

Phil's bosses asked him to develop a system that would solve their growing problems. As always, they gave him two months to complete a project that needed six. (Bosses putting ambiguous, over-ambitious deadlines on a developer? Never heard of that!) In addition, his bosses asked if the Internet could be used as the means of communication between the retail stores and the telephone center. In response, Phil decided to research COM and see how it could be used with Visual Basic (since most of his developers were Visual Basic programmers). He concluded that he would implement COM-based techniques to solve their problems. Throughout the rest of the book, I will demonstrate some of the techniques Phil used to develop his solutions.

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This article was originally published on November 20, 2002

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