Porting VBDOS/QBasic Questions

[Chris Bradford]

Hi --

I'm exploring the capabilities of PB/DOS, as it may offer a solution
to a problem.

I'm currently maintaining a very large program, written in BASIC
that has a number of quirks that are making it difficult to port.

The appliocation is approx. 15 years old, and now consists of 500+
executibles. We compile it with the VBDOS compiler, although we
don't take advantage of any of the "visual" stuff... so basically,
its nothing more than a glorified QB45 program. It would probably
compile under QB45.

I have a few questions and I hope I get good answers!

1. Max code segment size with PB/DOS? One problem we have with
a program right now is that the code segment (compiled) hits
the 64k segment limit of the VBDOS compiler, and hence, won't compile.

2. CHAIN compatibility with VBDOS compiled programs? Can one program
compiled under VBDOS CHAIN to a program compiled with PB/DOS?

3. Libraries: support for QB and VBDOS style .LIBs?

4. Variable naming "challenges"... This is probably the worst aspect
of the code I"m maintaining! Some variables have the same name, but
different types. Under the VBDOS compiler, n#, n%, and n$ are recognized
as 3 different vars. Some compilers don't deal with this, and it's
a poor programming practice... how does PB/DOS deal with this?

I don't think PB/CC is an option for this program because there are too
many low level DOS dependencies.

Regards

--Chris Bradford

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[Tom Hanlin]

In DOS, a segment can only cover a range of 64k. PB/DOS can't change that.
However, you can use the $SEGMENT metastatement to divide your code into
multiple segments.

CHAIN is compiler-dependent. You can't mix and match VB/DOS and PB/DOS
chained units. If you don't have any values to transfer between programs,
or can store them in a file rather than using COMMON blocks, you can use
RUN instead of CHAIN. RUN is not compiler-dependent.

PowerBASIC uses .PBL libraries. These are not compatible with .LIB or .QLB
libraries.

PB/DOS has no problem with variables of the same name but different type.

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Tom Hanlin
PowerBASIC Staff