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FAQ: (6/94) comp.lang.basic.visual.* VB/DOS Frequently Asked Questions


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Last-Modified: June 10, 1994

                   VISUAL BASIC FOR DOS (VBDOS)
                Commonly asked Questions & Answers
                         Section IX - B
               -----------------------------------

PREFACE:
This document is a compilation of frequently asked questions and their
answers about Visual Basic for DOS which have been gathered from the
comp.lang.basic.visual newsgroup.   Although some efforts have been
made to find obvious errors, there is no guarantee that the information in
this document is error-free.  The FAQ maintainer, or anyone else
associated with this document, assume NO liability for the content or use
of this document.  If you find any errors, please report them to the address
given below.

Most FAQs (including this one) are available at the anonymous ftp archive
site "rtfm.mit.edu".  All four parts of the VB FAQ may be found in the
directory "pub/usenet/news.answers/visual-basic-faq".

You can also have the VB FAQs e-mailed to you by sending a message
to "mail-server@rtfm.mit.edu" with ONLY the text "send
usenet/news.answers/visual-basic-faq/*" in the body of the message.

As the FAQ maintainer, I don't have time to explore all of the aspects of
Visual Basic.  I rely on your submissions to improve the quality and
inclusiveness of this document.  If you have found a VB hint, tip, trick,
work-around, etc., please write it up and send it to me!
  Peter Millardac150@freenet.buffalo.edu   - VBDOS FAQ maintainer

Table of Contents:
1.   How do I use (create) global variables in VBDOS?
2.   Does VBDOS make standalone .exe files?
3.   What is the current version of the VBDOS compiler?
4.   How do I not make a text box beep when I hit the enter key?
5.   How does Visual Basic handle shelled tasks? How do I find out
     when they are finished.
6.   How do I break lines of long text into multiple lines of text in
     the msgbox?
7.   What's the difference between MODAL and MODELESS
     forms?
8.   When/Why should I use Option Explicit?
9.   Why doesn't PRINT or CLS from a frm module work?
10.  How do I invoke FKey traps which won't be triggered by other
     keys which share the same KeyCode?
11.  How do I boost memory available to VBDOS.EXE (the IDE)?
12.  My program runs in the IDE, but won't run when compiled??
13.  MISC. Programming TIPS:

-----------------------------------------------------------------------------

1.   How do I use (create) global variables in VBDOS?
     1.1. VBDOS provides the user with two types of global variables.
          These are both used in declarations of variables.

          To share variables between all subs and functions in a specific
          module, use the SHARED keyword. This makes that specific
          variable global _in that module_. For example:

                  DIM SHARED CancelFlag AS INTEGER

          would make the variable CancelFlag a global variable in that
          module.

          To share global variables between separate modules, use the
          COMMON keyword. For example:

                 COMMON SHARED CancelFlag AS INTEGER

          would make the variable global between all modules that this
          common statement appears in, and since we are using the
          SHARED keyword also, this will also be shared in all the subs
          and functions in the modules which this declare statement
          appears. All COMMON statements must be matched between
          modules which the variables should be global in. For example,
          if you have one set of 10 COMMON statements in one module,
          and a different set of 10 COMMON statements in another
          module in the same project, you will get a 'Type Mismatch
          Error'. Make all COMMON blocks identical in all the modules
          in a specific project. (See Misc. Programming Tips Below).

2.   Does VBDOS make standalone .exe files?
     2.1. VBDOS can compile programs in two different ways (user
          option). It can compile programs to use a RUNTIME file (like
          a DLL) or can be compiled as a standalone .exe file. 

3.   What is the current version of the VBDOS compiler?
     3.1. VBDOS is currently at version 1.0

4.   How do I not make a text box beep when I hit the enter key?
     4.1. Put "something else" in your _KeyPress event, depending on
          what you really want. This code example makes *nothing*
          happen, for an extended period of time:

          Sub Text1_KeyPress (KeyAscii As Integer)
              If KeyAscii = 13 Then   '13 is Key_Return
                   KeyAscii = 0  '0 (zero) is nothing
              End If
          End Sub

          This might not be a very nice thing to do, since your users
          usually have some intention when they press Enter. Usually
          they will want to jump to the next control, like the Tab key
          does. You will then change the line KeyAscii=0 to KeyAscii=9
          (Key_Tab) in the example above. 

          BTW, you'll also find this in the Microsoft VB
          KnowledgeBase. They add that you should set the MultiLine
          property to False. Of course.

5.   How does Visual Basic handle shelled tasks? How do I find out
     when they are finished.
     5.1. In VBDOS, all shelled tasks are completed before control
          returns to the program. No tasks are done while the DOS
          command is being executed.

6.   How do I break lines of long text into multiple lines of text in the
     msgbox?
     6.1. Use the append a chr$(13) to the end of the string to break
          lines into multiple lines. EG:

               msg$ = "This is line 1" + chr$(13)
               msg$ = msg$ + "This is line 2"
               MSGBOX msg$

7.   What's the difference between MODAL and MODELESS forms?
     7.1. Modal forms are forms which require user input before any
          other actions can be taken place. In other words, a modal form
          has exclusive focus until it is dismissed. When showing a
          modal form, the program pauses at the SHOW command until
          the modal form is either hidden or unloaded. The internal
          MSGBOX and INPUTBOX$ forms are examples of modal
          forms. To show a form modally, use the syntax:
          MyForm.SHOW 1

     7.2. Modeless forms are those which are shown but do not require
          immediate user input. Most child forms (in a MDI application)
          are typically modeless. To show a form modeless, use the
          syntax: MyForm.SHOW

8.   When/Why should I use Option Explicit?
     8.1. Opinions vary greatly on this subject. The main reason to use
          the OPTION EXPLICIT statement at the top of all modules is
          to minimize the amount of bugs introduced into your code by
          misspelling a variable name. Most variants of BASIC
          (including VB) have the capability to create variables 'on the
          fly' (without any declarations). This capability can be a double
          edged sword.

          At the minimum, it is suggested to use the DEFINT A-Z
          statement in leu of OPTION EXPLICIT. This statement will
          cause any variables which are created on the fly to be created
          as integers as opposed to single precisions. (Integers take up
          less memory). 

          The OPTION EXPLICIT statement causes VB to 'disable' it's
          ability to create variables on the fly. Thus, all variables must be
          declared using a DIM or REDIM statement. All variables not
          declared will cause an error when the OPTION EXPLICIT
          statement is used. This will eliminate any bugs when a variable
          is misspelled.

9.   Why doesn't PRINT or CLS from a frm module work?
     9.1. To print information to the screen bypassing the desktop, the
          commands must be issued from a .BAS module. All
          PRINT/CLS output from a form module is directed to the nul:
          device.

10.  How do I invoke FKey traps which won't be triggered by other keys
     which share the same KeyCode?
     10.1.     To trap the only FKeys in events you need to use a
               combination of the KeyDown, KeyPress, and KeyUp
               events. 

          The basic concept for this is that _all_ keys trap the UP &
          DOWN events, while only 'printable' characters trigger the
          KeyPress event. Thus, when a character key is pressed, it will
          trigger the KeyDown, the KeyPress, then the KeyUp events (in
          that order). While a FKey (or arrow, or tab, etc...) will trigger
          the KeyDown, then the KeyUp events (in that order). 

          The following code uses a textbox tag property to decide
          whether a printable character is pressed or not.

               SUB Text1_KeyDown()
                    Text1.tag = "key"
               END SUB

               SUB Text1_KeyPress()
                    Text1.tag = ""
               END SUB

               SUB Text1_KeyUp()
                  IF Text1.tag = "key" then
                    '--PUT F-KEY HANDLER HERE----
                  ELSE
                    '--PUT OTHER KEY HANDLERS HERE----
                  END IF
               END SUB

11.  How do I boost memory available to VBDOS.EXE (the IDE)?
     11.1.     Try to have as much EMM available as possible.
               VBDOS.EXE allocates subroutines & functions which are
               < 16K into EMM.
     11.2.     To make more conventional mem availble, use the /S:n
               switch. This will make VBDOS.EXE use a specific
               amount of conventional memory. A good compromise
               between speed & memory is /S:340. The lower the n
               value, the slower the environment runs.
     11.3.     Running out of DGROUP usually causes most 'out of
               memory' errors. Possible causes are:
          11.3.1.Too many subs & functions exist. Each one takes up
               46 bytes of DGROUP.
          11.3.2.   Large static arrays. All static arrays are stored in
                    DGROUP. If a DIM statement is for a COMMON
                    SHARED statement, the array becomes static. Make
                    the COMMON SHARED statement appear before
                    the DIM statement to make the array Dynamic &
                    therefore will not be stored in DGROUP.
          11.3.3.   Variable Overhead. Each var has a 4 byte overhead
                    for _each_ module. For multiple modules projects
                    which use lots of Global (COMMON) statements,
                    this overhead is repeated for _each_ module.
     11.4.     Possible causes for running out conventional memory:
          11.4.1.   Not enough EMM.
          11.4.2.   Subs or functions which exceed 16K.
          11.4.3.   Large arrays. Non-variable length string arrays can
                    be stored in EMM using the /ea switch.

12.  My program runs in the IDE, but won't run when compiled??
     12.1.     Arrays are dynamic by default in the IDE, but when they
               are compiled, they are static by default. Therefore, they
               are stored in DGROUP instead of the far heap. Use
               '$DYNAMIC to make all arrays dynamic or use REDIM
               instead of DIM.
     12.2.     Program generates a "program memory overflow" during
               compile. You need to break a single module into multiple
               ones.

     
13.  MISC. Programming TIPS:
     13.1.     When useing the form designed, to continuously draw
               controls of a specific type, hold down the control key
               when clicking on the appropriate control from the tool-
               box.
     13.2.     Use the INCLUDE statement to manage large numbers of
               COMMON SHARED statements, user defined data types,
               or external function DECLARES. To use an include file,
               simply put all the VBDOS statements that will be shared
               into a single file. Save the file as something appropriate.
               (Typical naming convention is to use an extension of .BI
               for basic include files). Then simply insert the line:
                        'INCLUDE: 'foobar.bi'
               into either your .BAS module, or the module level code
               in a form. 

-- 
Kris Nosack      knosack@park.uvsc.edu

>>>--->  Be strange, but not a stranger!  <---<<<

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