Writing Console-Mode Applications in Visual Basic

By Scott Lloyd

To set everything straight, here is the example program. This program will print a prompt asking a user to enter a name. After a user enters his name the program prints a greeting and waits until the user is ready to quit.

'+================================================
' File: Console.bas
'
' Summary: Demonstrates how it is possible to
' create and manipulate a console box in Visual
' Basic.
'
' Classes: None
'
' Functions: Main, ConsolePrint, ConsoleRead
'
' Origin: Visual Basic 6.0 For Windows
'
'------------------------------------------------------
' (C) Copyright 1999 by Scott Lloyd. All Rights
' Reserved.
' Scott Lloyd 
'=====================================================+

Option Explicit
'''''D E C L A R A T I O N S'''''''''''''''''''''''''''

Private Declare Function AllocConsole Lib "kernel32" _
    () As Long

Private Declare Function FreeConsole Lib "kernel32" _
    () As Long

Private Declare Function GetStdHandle Lib "kernel32" _
(ByVal nStdHandle As Long) As Long

Private Declare Function ReadConsole Lib "kernel32" _
    Alias "ReadConsoleA" (ByVal hConsoleInput As Long, _
    ByVal lpBuffer As String, ByVal nNumberOfCharsToRead _
    As Long, _
lpNumberOfCharsRead As Long, lpReserved As Any) As Long

Private Declare Function SetConsoleMode Lib "kernel32" (ByVal _
hConsoleOutput As Long, dwMode As Long) As Long

Private Declare Function SetConsoleTextAttribute Lib _
"kernel32" (ByVal hConsoleOutput As Long, ByVal _
wAttributes As Long) As Long

Private Declare Function SetConsoleTitle Lib "kernel32" Alias _
"SetConsoleTitleA" (ByVal lpConsoleTitle As String) As Long

Private Declare Function WriteConsole Lib "kernel32" Alias _
"WriteConsoleA" (ByVal hConsoleOutput As Long, _
ByVal lpBuffer As Any, ByVal nNumberOfCharsToWrite As Long, _
lpNumberOfCharsWritten As Long, lpReserved As Any) As Long

''''C O N S T A N T S'''''''''''''''''''''''''''''''''''''
'I/O handlers for the console window. These are much like
'the hWnd handlers to form windows.

Private Const STD_INPUT_HANDLE = -10&
Private Const STD_OUTPUT_HANDLE = -11&
Private Const STD_ERROR_HANDLE = -12&

'Color values for SetConsoleTextAttribute.
Private Const FOREGROUND_BLUE = &H1
Private Const FOREGROUND_GREEN = &H2
Private Const FOREGROUND_RED = &H4
Private Const FOREGROUND_INTENSITY = &H8
Private Const BACKGROUND_BLUE = &H10
Private Const BACKGROUND_GREEN = &H20
Private Const BACKGROUND_RED = &H40
Private Const BACKGROUND_INTENSITY = &H80

'For SetConsoleMode (input)
Private Const ENABLE_LINE_INPUT = &H2
Private Const ENABLE_ECHO_INPUT = &H4
Private Const ENABLE_MOUSE_INPUT = &H10
Private Const ENABLE_PROCESSED_INPUT = &H1
Private Const ENABLE_WINDOW_INPUT = &H8
'For SetConsoleMode (output)
Private Const ENABLE_PROCESSED_OUTPUT = &H1
Private Const ENABLE_WRAP_AT_EOL_OUTPUT = &H2

'''''G L O B A L S'''''''''''''''''''''''''''''''''''
Private hConsoleIn As Long ' The console's input handle
Private hConsoleOut As Long ' The console's output handle
Private hConsoleErr As Long ' The console's error handle

'''''M A I N'''''''''''''''''''''''''''''''''''''''''
Private Sub Main()
Dim szUserInput As String

AllocConsole ' Create a console instance

SetConsoleTitle "VB Console Example" 'Set the title on
                                     'the console window

'Get the console's handle
hConsoleIn = GetStdHandle(STD_INPUT_HANDLE)
hConsoleOut = GetStdHandle(STD_OUTPUT_HANDLE)
hConsoleErr = GetStdHandle(STD_ERROR_HANDLE)

'Print the prompt to the user. Use the vbCrLf to get
'to a new line.
SetConsoleTextAttribute hConsoleOut, _
FOREGROUND_RED Or FOREGROUND_GREEN _
Or FOREGROUND_BLUE Or FOREGROUND_INTENSITY _
Or BACKGROUND_BLUE

ConsolePrint "VB Console Example" & vbCrLf
SetConsoleTextAttribute hConsoleOut, _
FOREGROUND_RED Or FOREGROUND_GREEN _
Or FOREGROUND_BLUE
ConsolePrint "Enter your name--> "

'Get the user's name
szUserInput = ConsoleRead()
If Not szUserInput = vbNullString Then
ConsolePrint "Hello, " & szUserInput & "!" & vbCrLf
Else
ConsolePrint "Hello, whoever you are!" & vbCrLf
End If

'End the program
ConsolePrint "Press enter to exit"
Call ConsoleRead

FreeConsole ' Destroy the console
End Sub

'''''F U N C T I O N S''''''''''''''''''''''''''''''''''

'F+F+++++++++++++++++++++++++++++++++++++++++++++++++++
' Function: ConsolePrint
'
' Summary: Prints the output of a string
'
' Args: String ConsolePrint
' The string to be printed to the console's ouput buffer.
'
' Returns: None
'
'-----------------------------------------------------

Private Sub ConsolePrint(szOut As String)
WriteConsole hConsoleOut, szOut, Len(szOut), vbNull, vbNull
End Sub

'F+F++++++++++++++++++++++++++++++++++++++++++++++++++++
' Function: ConsoleRead
'
' Summary: Gets a line of input from the user.
'
' Args: None
'
' Returns: String ConsoleRead
' The line of input from the user.
'---------------------------------------------------F-F

Private Function ConsoleRead() As String
Dim sUserInput As String * 256
Call ReadConsole(hConsoleIn, sUserInput, _
    Len(sUserInput), vbNull, vbNull)
'Trim off the NULL charactors and the CRLF.
ConsoleRead = Left$(sUserInput, InStr(sUserInput, _
    Chr$(0)) - 3)
End Function

That about does it. The code is well documented so there isn't much to be explained. If you have any questions or comments, you can contact me at scott@talker.com.

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