Visual Basic (VB) is a general object-based programming language developed by Microsoft Corporation. It is a structured, modular, and object-oriented visual programming language that includes an event-driven mechanism to assist the development environment. VB is commonly used for developing applications within the Microsoft ecosystem.
The term "Visual" refers to the ability to develop a graphical user interface (GUI) without writing extensive code to describe the appearance and location of interface elements. Instead, developers can simply add pre-built objects to the screen. The term "Basic" refers to the BASIC (Beginners All-Purpose Symbolic Instruction Code) language, which was one of the most widely used programming languages in computing history.
Visual Basic evolved from the BASIC programming language. It features a graphical user interface (GUI) and a rapid application development (RAD) system. This allows developers to easily connect to databases using technologies like DAO, RDO, ADO, or create ActiveX controls for efficient generation of type-safe and object-oriented applications. Programmers can quickly build applications using the components provided by VB.
[Image: Summary of VB language knowledge points]
**Summary of VB Language Knowledge Points**
**1 Chapter 1 Knowledge Points**
**(1) Language Features of VB**
- Visual Development Environment: What you see in the interface design.
- Object-Oriented Programming: Programs and data are encapsulated as objects. For example, the CommandButton class in the toolbox becomes an object named Command1 when dragged out.
- Event-Driven Programming: VB programs do not have a clear entry or exit point. They wait for events triggered by users, systems, or code, and then perform the corresponding tasks.
**(2) Working Mode of VB**
- Design Mode: Used for designing the application interface.
- Run Mode: Used for running the application. No code or interface modifications can be made during this mode.
- Interrupt Mode: Allows for debugging and testing.
**(3) VB File Types**
- Form file (.frm): Stores the form design.
- Program module file (.bas): Contains standard code modules.
- Class module file (.cls): Defines custom classes.
- Project file (.vbp): Represents the entire project.
- Project group file (.vbg): Manages multiple projects.
- Resource file (.res): Contains resources such as icons and images.
**(4) VB Windows**
- Any closed window can be found under the View menu.
- Toolbox Window: Contains all available controls.
- Code Window: Where the code is written.
- Form Layout Window: Displays the layout of forms.
- Immediate Window: Used to query object values during debugging (Ctrl+G opens it).
**2 Chapter 2 Knowledge Points**
**(1) The Basic Concept of Object-Oriented Programming**
- Classes: Abstractions of objects with similar properties and methods.
- Objects: Instances of classes. Each object has its own properties and methods.
- Attributes: Static features of an object, such as name.
- Events: Effects on an object, such as Load, Unload, Click.
- Methods: Behaviors of an object, such as Move, Show, Hide.
**(2) VB Development Process**
1. Analyze and draw flowcharts.
2. Design the interface.
3. Write the code.
4. Test and run the application.
**3 Chapter 3 Knowledge Points**
**(1) Format of VB Writing Code**
- Case-insensitive: VB code is case-insensitive.
- Multiple statements on one line: Separated by a colon (:).
- Line continuation: Use an underscore (_).
- Comments: Start with Rem or use single quotes (').
- Block comments: Available in VB6 via the Edit menu.
**(2) Basic Data Types of VB**
- Value types include Integer, Double, String, Date, etc.
- String Type:
- Declared with double quotes ("").
- Example: `Dim s As String` or `Dim s As String * 8`.
- Date Type:
- Delimited with #.
- Example: `Dim a As Date`, `a = #4/20/1999#`.
- Object Type:
- Variables reference various objects.
- Example: `Dim a As CommandButton`, `Set a = Command1`.
- Variant Type:
- Can hold any data type.
- Example: `Dim a`, `a = "88"`, `a = a + 10`.
**(3) Declaration of VB Constants**
- Symbolic constants: Declared with `Const`, must be initialized.
- Examples:
- `Const a As String = "123"` (explicit)
- `Const a = True` (implicit)
**(4) Declaration of VB Variables**
- Variables declared with `Dim`, must be defined before use.
- Examples:
- `Dim a As Double`
- `Dim a%, b#`
**(5) VB Operators**
- Arithmetic Operators: `() ^ * / \ Mod + -`
- Relational Operators: `> >= < <= = <>`
- Logical Operators: `Not And Or Xor Eqv Imp`
- Operator Priority:
- Highest: Arithmetic operators
- Lowest: Logical operators
**(6) VB Functions**
- Mathematical Functions:
- `Abs`: Returns absolute value.
- `Int`: Rounds down.
- `Fix`: Rounds towards zero.
- `Exp`: Returns e raised to a power.
- `Log`: Returns natural logarithm.
- String Processing Functions:
- `Len`: Returns string length.
- `Trim`: Removes leading/trailing spaces.
- `String`: Repeats a character.
- `Lcase`: Converts to lowercase.
- `Ucase`: Converts to uppercase.
- `Left`: Returns left portion of a string.
- `Right`: Returns right portion of a string.
- `Mid`: Returns substring from a position.
- `Instr`: Returns position of a substring.
- Date Functions:
- `Date`: Returns current date.
- `Time`: Returns current time.
- Type Conversion Functions:
- `CStr`: Converts to string.
- `Val`: Converts to number.
- `Rnd`: Generates random numbers.
**4 Chapter 4 Knowledge Points**
**(1) InputBox Function**
- Used to receive input from the user.
- Syntax: `InputBox("Prompt", "Title", "Default")`.
- Returns a string, often converted to a number using `Val`.
**(2) MsgBox Function**
- Used to display messages and get user feedback.
- Syntax: `MsgBox("Message", Buttons + Icons + DefaultButton, "Title")`.
- Returns an integer representing the button clicked.
**(3) MsgBox Statement**
- Similar to `MsgBox` function but does not return a value.
**(4) Print Method**
- Used to output data to a form or printer.
- `Print` alone prints a blank line.
- `Print ;` outputs in a row.
- `Print` adds a space after each item.
- `Tab(n)` sets absolute distance.
- `Spc(n)` sets relative distance.
**6 Chapter 6 Knowledge Points**
- **Label**: Displays text, supports transparency.
- **Text Box**: Allows input and displays text, supports password characters.
- **Command Button**: Triggers actions when clicked.
- **Timer**: Executes code at intervals.
- **PictureBox**: Displays images.
- **Option Button**: Selects one option from a group.
- **Check Box**: Allows multiple selections.
- **Scroll Bar**: Adjusts values through sliding.
- **List Box**: Displays a list of items.
- **Combo Box**: Combines a text box and list box.
**7 Chapter VII Knowledge Points**
- Focuses on writing programs and applying them flexibly.
- Program structures: Sequential, Conditional, Loop.
- Conditional Structures:
- `If...Then`
- `If...Then...Else`
- `Select Case`
- Loop Structures:
- `For...Next`
- `While...Wend`
- `Do...Loop`
- `GoTo` statement for jumping to labels.
**8 Chapter 8 Knowledge Points**
- **Array Declaration**:
- `Dim arrayName(start To end) As DataType`
- Example: `Dim a(1 To 10) As Integer`
- **Array Operations**:
- Assignment, reference, input, output, copy.
- **Bubble Sort Example**:
- Enter 10 numbers, find max, min, average, and sort using bubble sort.
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