Ask the MultiValued Visual Basic Expert - #8

(as published in Spectrum magazine)

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Copyright 1996-97 Caduceus Consulting. All rights reserved.

Laptops and AP/DOS

I often read your articles in Spectrum magazine and have some questions regarding a development issue. I have created a order processing application for laptops, written on AP/DOS. Merchants take their laptops in the field, enter orders, and perform various analyses based on downloaded data. That's all great, however, I would like to interface some Visual Basic programs with this AP/DOS database and have merchants run the VB programs. The host is the laptop. My questions are as follows:

  1. There are many laptops – are VB run-time licenses required to execute a VB program?
  2. Can a VB program work with AP/DOS or do I need to upgrade AP/DOS? Is that a costly upgrade for each laptop?
  3. Is D3 the only way to upgrade a PICK application running from windows? Currently they are using Windows 3.1. Do I have to upgrade them to Windows 95 in order to use any VB interface?

I know that's a lot of questions, but if you can help me, I would surely appreciate it. Thanks. - M. Margulis, New York

Thanks for your questions – I'm always happy to help out developers like yourself in any way that I can, so let's see what I can tell you:

Are VB run-time licenses required to execute a VB program?

Nope. You just need one copy of the Visual Basic software to develop and compile the EXE file that you can give to anyone as many times as you like. VB executables DO require a one-time installation of some VB functionality files, but these are freely distributable as well, and VB comes with a setup wizard that can take care of all of that for you.

Can a VB program work with AP/DOS or do I need to upgrade AP/DOS? Is that a costly upgrade for each laptop?

To my knowledge, VB cannot access AP/DOS files directly without some extra 'middleware'. The only two middleware products that I know of that can connect VB to AP/DOS are CuebicX from Cuebic Systems (using objects), and WinLink from Via Systems (using direct access, objects, or ODBC). You say that the laptop is the host, but you imply that data is still downloaded from another central source. Let's look at two scenarios:

If each laptop has a copy of AP/DOS then it might get a bit expensive for each laptop to get a full-blown server copy of the required middleware. If the laptops can be upgraded to Windows 95, you might consider getting a copy of D3 for Windows 95 for each laptop. That might be even more expensive than the middleware, but it would be a more elegant solution under those circumstances. Visual Basic can access data from D3 directly. I don't favor this solution because each laptop would be running as a fully independent host with a separate copy of all of the required data.

If the laptops can dial in to a central AP (or other MultiValue flavor) system (either directly or through the internet), then I would recommend that scenario. That way, the data is always current, and no big data download or expensive software is required. Each laptop would simply require a copy of your VB program and a single workstation license for the required middleware (which would be vastly cheaper). The future is heading back to centralized databases, where we were 15 years ago. If you didn't want to connect up every time, you could use ODBC or some other similar transport to grab selected data from the central host and store it on the laptops for future use.

Is D3 the only way to upgrade a PICK application running from windows? Currently they are using Windows 3.1. Do I have to upgrade them to Windows 95 in order to use any VB interface?

Is D3 the only way? No, it's not (unless you ask Pick Systems, of course!). There are many terminal emulators that will allow you to make your existing screens look like they have a graphical Windows interface. As for a full MultiValue system, running under Windows, early players in this market were jBASE (from JAC), and uniVerse NT from VMark. D3 runs under Windows 95 or NT. I believe UniData also put out an NT version of their flavor, but I have never worked with it, and now that they are teamed up with VMark, I don't know what will be happening with that. General Automation created a new NT-based MultiValue environment called mvŸ BASE, and finally the UniVision flavor from EDP was also just recently announced as available under NT. Each NT-based MultiValue database takes a different (sometimes radically different) approach to their particular implementation methodology.

I presume that you do have a central host, although you don't say what MultiValue flavor it is. Fortunately, if you are connecting the laptop to a remote MultiValue host, then middleware like CuebicX and WinLink will talk to just about any flavor, from the old Sanyo Icons and PI/Open boxes right up to the latest D3 and uniVerse NT boxes.

Whether you have to upgrade the laptops to Windows 95 or not depends on the version of VB that you use. Applications written with VB4 (16-bit) can run under Windows 3.1, 3.11, 95, or NT. VB5 applications will ONLY run under Windows 95 or NT. My advice for you? If you can find a copy of VB4 (Professional edition), buy it. In my opinion, while the code editor in VB5 is a little more helpful, the improved functional capabilities are not that noticeable for a beginning VB developer, and with VB5 you lose the O/S choice that 16-bit VB4 continues to offer you. Furthermore, you can always go from 4 to 5, but you can't go back! (Of course, the value of this advise will diminish with time as 16-bit systems continue to fade from the market.)

To email your questions to "Ask the MultiValued VB Expert", click here.
Copyright 1998 Caduceus Consulting. All rights reserved.
Compiled: May 6, 1998.

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