Review VB6.0

Review VB6.0 Second Revised Edition

1 MY®

MillenniumYear®

Your Success, Our Strength ™

Second Revised E-Edition

Second Edition

Standard: MY07/11

Serial Key: 2007RVB6P1070705000107

Rohit Birla


2 MY®

PREFACE:

VB is modified version of basic language. We have discuss here the basic visual basic version 6.0.

Questions and answers given here onemust try them on omputers. Try to beat microsoft simple projects

likenotepad, wordpad, word, excel and calculator etc… . reader must go with a basic VB book liike

mastering vb6 or peter norton to teach yourself VB or teach yourself VB in 21 days or black book and be

contineue with both book and these notes.

08 Oct,2009

Best of luck

CONTACT DETAILS:

[email protected]

[email protected]

Your suggestions are always invited.

Our projects in VB

Visual paint 1.0,2.0,3.0

Snake chess

Point gain

Cross road

Bow and arrow

Address book

Phone book

Ntepad

Code modeule

Editor

Applet editor

CBPO

Questionarries

SIS2007

SIS2008 (LOC 45k)

And many more…..

# we assume, you are comfortable with ‘C’ and have gone through Review ‘C’atleast once.

mailto:[email protected]

mailto:[email protected]


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Intro:

Many programmers tends to dive in and start coding right off bat, but you get into habit of planning like

sit down with blank sheet of paper and sketch out what user interface you want.

- Plan program tasks

- Design user interface

- Write program’s code

- Test and debug with beta version

- Document and distribute program

VB window:

- Menu bar

- Tool bar

- Tool box

- Form window

- Code window

- Project window

- Properties window

- Form window

Contents of tool box:

1. Pointer: used for selecting object placed on form. It is always selected.

2. Label: control display text on form that user can’t edit.

3. Textbox: that user can edit.

4. Picture Box: to display image.

5. Frames: acts as container for controls like option button or check box mainly.

6. Command button: represent an action that is carried out when user click on these acess key

be attach by using ‘&’ before character which you want to be shortcut key.

7. Checkbox

8. Option button

9. Combo box : list control + text box.

10. List box: display a list of item. User can select one or more options.

11. Scrollbars: vertical & horizontal.

12. Timer: 1000 = 1 sec.

13. Drive list, Dir list, file list => used together.

14. Shape: to draw box, circle, oval, rounded box.

15. Line: to draw line.

16. Image control: as picture box. Image control not have alignment property.

17. Data: used to access records from a database.

18. OLE: used to make a two way link with an object in other windows application.

(OBJECT LINKING AND EMBEDDING)


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VB window:

Variables:

Varibables are used for storing data. A varible has a name and a datatype.

The variable name is used to refer to value in variable and datatype determine the type of data the

variable cans store. A varibale is capable of storing

User supplied input

Intermediate results

Value returned by a function

Rules for variable name:

Must begin with a letter

Must not excceed 255 character

Cant be a reserver word

Must be unique in its scope

Declaring variables:

Vb provide us a facility to declare or not variable before complier use them., it’s a good practise

to declare varibales in advance for compiler (explicit declaration) so that compiler produce

efficient code.

Explicit declaration:


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o Dim var_name as integer

Implicit declaration:

o When vb meets undeclare variable then it will declare it on the spot.

o To declare a variable without declaring but of specific datatype, we use suppix like $ for

string, % for integers, & for long, ! for single and # for double.

o Use defxxx statement like defint a-c. now any variable starting with a,b,c, will be of

integer type.

To make explicit declaration, we write option explicit in first line of code window.

Scope of the variables:

Private: declare using dim statement and use only for single procedure and scope is local to that

procedure only.

Module: declare using private or dim, delcare at top of code window, use by all procedure in

that code window

Public: declare using public keyword, can be use by all forms and all procedures in all modules of

project or application.

Datatypes in VB:


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Converting variable types:

cbool boolean

cbyte byte

ccur curency

cdate date

cdbl double

val/cint integer

clng long

csng single

cstr string

cstr string

cvar variant

cverr Error First vb program:

1. Drag and drop three text box on your form and then four command button as shown in figure

2. Select command1 and change its caption property ot ‘+’, same with command2 ‘-‘, command3

‘*’ and command 4 ‘/’.

3. Double click on command1 and in code window write,

Text3.text=cint(text1.text) + cint(Text2.text)

Follow same for command2, write – in between, for command3, write * and command4 for /

4. Press F5, then write a number in text1, second number in text2, press +, -, *, / , to see result


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If-else:

Msgbox:

Print statement:

Use for printing on form:

o print “hello”

o print a

printing on printer

o printer.print text1.text

printing in a file:

o print #nfile, “hello how are you”


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Structure of VB program:

Varible declaration

Subroutines or functions

Procedures

Built in datatype:

Like integer, string, object, boolean etc…

User defined types:

Try yourself

Find largest in three numbers

Accept a name from user and display it in message box

Display grade and percentage of a student


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Arrays:

Occupy continuous memory. Each element in array is referenced by same name and index value.

Dim <array name> (size) as type

Ex: dim a(20)as integer

Note: these array elements are referenced as a(1),a(2) etc… and a(20) means it will save 0 to 20

elements.

1. Array with base1:

Write ‘option base 1’ between array declaration, and all arrays will start from 1 not with

zero.

2. Declaring lower and upper bound:

Dim marks (10 to 20) as integer. Now lowerbound=10 and upperbound=20

3. Checking lower and upper bound:

a. Msgbox a.lbound

b. Msgbox a.ubound

4. Declaring dynamic array:

1. Dim a() as integer

2. Redim a(20) (it will lost all data)

3. Redim preserve a(16) (to save data)

Multi dimension array:

a) Dim r(2,2) as integer

b) Dim mat(1 to 3, 1 to 4) as integer

c) Dim add(3,4,5,6) as integer

There is no limit on number of dimensions in VB

Control arrays:

1. Copy textbox (which is on form) and paste on form. It will give a message, do you want to

create control array, say yes. Now both textbox have same name ‘text1’ but differ by their

index value 0 and 1 respectively.

2. Similarly try to create control array of label, command button etc…

3. Load statement are used to create run time control arrays

a. Load text1(k)

b. Unload text1(k)


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Static and dim variables:

static preserves their last values while dim not

Arithmetic operators:

^ exponential

+ add - minus * multiply / division \ integer division

mod reminder

Boolean operators:

< less than > greater than <= less than equal to >= greater than equal to

= equal to <> non equal to

Logical operators: AND OR NOT

Concatenation operator:

Dim s as string S=”hello” S=s & “!” & “how are you” Print s S = s & “a=” & a & “b=” & b Print s ‘ VB is case – insensitive language


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Looping:

Try to solve:

1. Implement control arrays for run time

2. Perform arithmetic operations

3. Implement static and dim in your program and find

difference

4. Give an example for and, or and not operator


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Properties of control arrays:

a control array have at least one control element and can grow up to 32767 elements

each control must be of same type

each control have same property (name)

each control is identified by unique index value

we can remove only those controls which are added at run time

we usually make control arrays differ by top and left properties

Subroutine and function:

function can return a value while subroutine not

function define with keyword function and subroutine by sub

both makes program understandable

both can be private or public

both can be called by each other


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Events:

An event is user action directed at application like clicking with mouse. VB has given subroutines

or events handlers for handling events. The combination of control name and events name is unique.

There are many types of events like of mouse - click, dbclick, mouse down, mouse up etc…

Form events: initialize, load,activate, gotfocus, drag,drop,resize,deactivate and unload

Form methods: hide,show,unload and end

Q: try to use show and hide functioning

Properties of form: backcolor, borderstyle,caption, forecolor, control box, name, window state

Scale modes: have you noticed that scalex, scaley, scale width, scale height. Change these properties

and check difference.

With statements:

To change multiple properties of a control, we use with statement like:

With text1

.name=”text”

.caption=”hello”

.forecolor=vbred

End with

1. Try to pass array in a function

2. Find factorial of a number

3. Write Fibonacci sequence

4. Check built in inputbox function

5. Procedures can be private or public, describe with example

6. How to check return values of msgbox function

7. Make a function that swap two values


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Printer object:

printer.print “hello”

printer.print str

printer.print text1.text

printer.fontname=”Tahoma”

printer.fontsize=16

printer.font bold=true

printer.new page

printer.enddoc

printer.line(x1,y1)-(x2,y2),color

printer.circle(x,y),r,color

check other properties like fill color, fill mode, draw mode, draw width, draw style, scale mode

etc.

printer1.paint picture picture1.picture,x1,y1,width,height,x2,y2

printer.copies

printer.orientation=vbporlandscapre

a=printer.page

printer.port

printer.zoom

Q: find difference between picture box and image box

Colors:

vb has some built in color like vb red,vb blue, vbblack,vbwhite

Q: tryout common dialog boxes.

[hint: goto project menu, click components, select Microsoft common dialog control, click ok.

cd1.showcolor

Cd1.showopen

cd1.filename

cd1.showprint

cd1.showsave

cd1.color etc… try these out]


15 MY®

Picture box vs image control:

picture box have alignment property

size of picture is fix in picture box while image control can change sckretch property

in picture box, we can draw graphics like line etc..but not in image control

both are use for showing picture

both use load picture method for loading picture

MAPI:

Mail application programming interface, you can send-receive email via your vb application, but

it is not quite easy as it seems this control is related to outlook express and it is not quite handy if you

didn’t configure your setting in outlook express or so… it is basically a universal provider for shelring bits

of functionality in email applications such as outlook and outlok express etc…MAPI has been drastically

deemphasized in windows due to the outbreak of self spreading worms (email viruses). A modern easy

to use MAPI is CO.

MAPI is a system built into Microsoft windows that enables different email applications to work

together to distribute mail. as long both applications are MAPI enables, they can share mail message

with each other.

Q: what is API, write a short note on built in APIs

Q: creating menus [hint: click on menu tool box from tool bar,

& for alt enabling

-> for submenues ]


16 MY®

Error handling:


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Object oriented programming:

1. click project > add class module and create functions in it

2. call these functions by creating their objects, and that’s oops!

API examples:


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File handling:


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Currency control and locking:

It is mechanism used by DBMS for sharing of data. Atomicity, consistency and isolation are

achieved through currency control and locking. The amount of data that can be locked with single

instance or group of instance defines granularity of lock.

Page locking: all data on specific page are locked

Cluster locking: data cluster together and locked simultaneously

Class or table locking: all instances of either a class or table are locked

Object or instance locking: lock a single relation tuple in RDBMS or a single object in ODBMS

SDI vs MDI:

SDI have single data window ex: wordpad, notepad. You can open one document at a time. Single

document interface. Multiple document interface. One parent form and that form contain other forms

and control them known as child form ex: word

Features of MDI:

1. an application can have only one MDI parent form

2. MDI contain only those controls that supports alignment property

3. We can’t display information on MDI form

4. MDI and all child of it represent single icon on taskbar

5. When a child is minimized, all its child form minimized and also parent

6. Parent visible in taskbar

7. When a child is maximized, it cover entire area of parent form

8. Two unique properties of MDI

a. Auto show child: if true, then when parent opened, child itself displayed

b. Scroll bar: if true, then if child exceed beyond boundary of parent, then scrollbar is

shown

1. Try to beat Microsoft standard calculator

2. Try to implement notepad and address book

3. Make a program that run in startup and add your daily used

features in it, so no more start menu, no window, now every

thing in a lick in front of you.

4. Try to implement code module for C/C++


20 MY®

Send keys:

Is a module for windows which can be used to send one or more keystrokes or their combination to

active window.

+ shift

^ ctrl

% alt

ctrl a given as ^a

shift abc is given as +{ABC}

{BACKSPACE}

{BREAK}

{CAP}

{DOWN}

{DEL}

{up}

{LEFT}

{RIGHT}

{HOME}

{END}

{HOME}

{LWIN}

{RWIN}

{ADD}

{MULTIPLY}

{DIVIDE}

{SCROLLLOCK}

{PRTSC}

{NUMLOCK}

{PAGEUP}

{PAGEDOWN}

{INSERT}

{ESC}

{F1}…{F24}

{TAB}


21 MY®

Q: open notepad, write hello to it and close it without saving

Ans: import sendkeys Sendkeys.sendkeys { “”” {LWIN} {PAUSE .25} R NOTEPAD.EXE {ENTER} {PAUSE 1} HELLO {PAUSE 2} %{F4} N “””}


22 MY®

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