Logo
Courses/Operating Systems 2

Lab 1: Introduction to Dart Programming

6 min read
Lesson slides
1 / 13

Lab 1: Introduction to Dart Programming

Variables, control flow, functions, and OOP in Dart — the language behind Flutter

Welcome to the first lab session for OS2. This lab introduces Dart, the programming language that powers Flutter. You will learn fundamental programming concepts including variables, control flow, functions, and object-oriented programming.

Table of Contents

  1. Prerequisites & Setup
  2. Introduction to Dart
  3. Variables and Data Types
  4. Decision Making and Loops
  5. Functions
  6. Object-Oriented Programming
  7. Lab Exercises
  8. Additional Resources

Prerequisites & Setup

Before starting with Dart programming, you need to set up your development environment.

Option 1: Using DartPad (Online - No Installation Required)

The easiest way to get started is using DartPad, an online Dart editor.

  1. Open your browser and navigate to https://dartpad.dev
  2. You can immediately start writing and running Dart code
  3. Perfect for quick experiments and learning

Advantages:

  • No installation required
  • Works on any device with a browser
  • Instant code execution

Limitations:

  • Limited features compared to full IDE
  • No project management capabilities

Option 2: Local Installation (Recommended)

For a complete development experience, install Dart and a code editor locally.

Step 1: Install Dart SDK

Windows:

  1. Download the Dart SDK from https://dart.dev/get-dart
  2. Alternatively, use Chocolatey package manager: 
    choco install dart-sdk
  3. Verify installation: 
    dart --version

macOS:

  1. Use Homebrew: 
    brew tap dart-lang/dart
brew install dart
  2. Verify installation: 
    dart --version

Linux (Debian/Ubuntu):

  1. Install via apt-get: 
    sudo apt-get update
sudo apt-get install apt-transport-https
wget -qO- https://dl-ssl.google.com/linux/linux_signing_key.pub | sudo gpg --dearmor -o /usr/share/keyrings/dart.gpg
echo 'deb [signed-by=/usr/share/keyrings/dart.gpg arch=amd64] https://storage.googleapis.com/download.dartlang.org/linux/debian stable main' | sudo tee /etc/apt/sources.list.d/dart_stable.list
sudo apt-get update
sudo apt-get install dart
  2. Verify installation: 
    dart --version

Step 2: Install a Code Editor

Visual Studio Code (Recommended):

  1. Download from https://code.visualstudio.com/download
  2. Install the Dart extension:
    • Open VS Code
    • Go to Extensions (Ctrl+Shift+X or Cmd+Shift+X)
    • Search for "Dart" and install the official extension by Dart Code

Android Studio (Alternative):

  1. Download from https://developer.android.com/studio
  2. Install the Dart plugin:
    • Go to File > Settings > Plugins
    • Search for "Dart" and install

Creating Your First Dart Project

Once you have Dart installed, you can create a project using the command line.

Step 1: Create a new project

dart create my_first_dart_project

Step 2: Navigate to the project directory

cd my_first_dart_project

Step 3: Run the default program

dart run

Understanding Project Structure

After creating a project, you will see the following directory structure:

graph TD
    A[my_first_dart_project/] --> B[bin/]
    A --> C[lib/]
    A --> D[test/]
    A --> E[pubspec.yaml]
    B --> F[my_first_dart_project.dart]
    C --> G[Library code]
    D --> H[Test files]
    E --> I[Dependencies & metadata]
    
    style A fill:#e1f5ff
    style B fill:#fff4e1
    style C fill:#fff4e1
    style D fill:#fff4e1
    style E fill:#e8f5e9

Directory Breakdown:

  • bin/: Contains the main executable file (entry point of your application)
  • lib/: Used for reusable library code
  • test/: Contains unit tests for your code
  • pubspec.yaml: Project configuration file (dependencies, metadata)

Running Dart Code

There are multiple ways to execute Dart programs:

Option 1: Run the entire project

dart run

Option 2: Run a specific file

dart run bin/my_first_dart_project.dart

Option 3: Execute a standalone Dart file

dart path/to/file.dart

Introduction to Dart

Dart is a general-purpose programming language with a C-style syntax. It supports modern programming concepts such as:

  • Classes and interfaces
  • Generics
  • Asynchronous programming
  • Strong typing with type inference

Key Feature: Dart does not support traditional arrays. Instead, it uses collections (Lists, Maps, Sets) to manage data structures.

Your First Dart Program

The entry point of every Dart application is the main() function:

void main() {
    print("Dart language is easy to learn");
}

Explanation:

  • void: The function does not return a value
  • main(): The entry point function
  • print(): Outputs text to the console

Variables and Data Types

In Dart, a variable is a named storage location, and data types define the size and type of data that can be stored.

Variable Declaration

var name = "Dart";        // Type inference
int age = 25;             // Explicit type
dynamic data = 100;       // Can change type at runtime

Constants

Use final or const to declare values that won't change.

Difference:

  • final: Value is set at runtime (can be computed)
  • const: Value is set at compile-time (must be a constant expression)
void main() {
    final a = 12;
    const pi = 3.14;
    print(a);
    print(pi);
}

Supported Data Types

Dart supports various built-in data types:

graph TD
    A[Dart Data Types] --> B[Numbers]
    A --> C[Strings]
    A --> D[Booleans]
    A --> E[Collections]
    A --> F[Dynamic]
    
    B --> B1[int - Integer values]
    B --> B2[double - Decimal values]
    
    E --> E1[List - Ordered collection]
    E --> E2[Map - Key-value pairs]
    E --> E3[Set - Unique values]
    
    style A fill:#4A90E2,color:#fff
    style B fill:#7ED321
    style C fill:#F5A623
    style D fill:#BD10E0
    style E fill:#50E3C2
    style F fill:#B8E986

1. Numbers

Dart supports two types of numbers:

int count = 10;           // Integer
double price = 99.99;     // Double (floating-point)

2. Strings

A sequence of characters enclosed in single or double quotes:

String message = "Hello, Dart!";
String name = 'Student';

String Interpolation:

String name = "Ahmed";
print("Hello, $name!");              // Output: Hello, Ahmed!
print("Next year I'll be ${25 + 1}"); // Output: Next year I'll be 26

3. Booleans

Represents true or false:

bool isStudent = true;
bool hasPassed = false;

4. Lists

Ordered collection of items (similar to arrays):

void main() {
    var list = [1, 2, 3, 4, 5];
    print(list);              // Output: [1, 2, 3, 4, 5]
    print(list[0]);           // Output: 1
}

5. Maps

Collection of key-value pairs:

void main() {
    var mapping = {'id': 1, 'name': 'Dart'};
    print(mapping);           // Output: {id: 1, name: Dart}
    print(mapping['name']);   // Output: Dart
}

6. Dynamic Type

If you don't specify a type, Dart uses dynamic:

void main() {
    dynamic name = "Dart";
    print(name);
    
    name = 100;  // Type can change
    print(name);
}

Decision Making and Loops

Control flow statements allow you to execute code based on conditions or repeat code blocks.

Decision Making Statements

Dart supports the following conditional statements:

  • if
  • if-else
  • else-if
  • switch

Example:

void main() {
    int score = 85;
    
    if (score >= 90) {
        print("Excellent");
    } else if (score >= 75) {
        print("Good");
    } else {
        print("Needs Improvement");
    }
}

Loops

Loops allow you to repeat a block of code multiple times.

Loop Flow Diagram:

flowchart TD
    A[Start Loop] --> B{Condition True?}
    B -->|Yes| C[Execute Code Block]
    C --> D[Update Counter]
    D --> B
    B -->|No| E[Exit Loop]
    
    style A fill:#4A90E2,color:#fff
    style B fill:#F5A623,color:#fff
    style C fill:#7ED321
    style E fill:#D0021B,color:#fff

Loop Types

1. for loop:

for (var i = 1; i <= 5; i++) {
    print(i);
}

2. for-in loop:

var list = [1, 2, 3];
for (var item in list) {
    print(item);
}

3. while loop:

int i = 1;
while (i <= 5) {
    print(i);
    i++;
}

4. do-while loop:

int i = 1;
do {
    print(i);
    i++;
} while (i <= 5);

Example: Print Even Numbers

The following code prints even numbers from 1 to 10:

void main() {
    for(var i = 1; i <= 10; i++) {
        if (i % 2 == 0) {
            print(i);
        }
    }
}

Output:

2
4
6
8
10

Functions

A function is a group of statements that performs a specific task. Functions help organize code and promote reusability.

Function Syntax

returnType functionName(parameters) {
    // Function body
    return value;
}

Example: Addition Function

void main() {
    add(3, 4);
}
 
void add(int a, int b) {
    int c;
    c = a + b;
    print(c);
}

Output:

7

Function with Return Value

int multiply(int a, int b) {
    return a * b;
}
 
void main() {
    int result = multiply(5, 3);
    print("Result: $result");  // Output: Result: 15
}

Object-Oriented Programming

Dart is an object-oriented programming (OOP) language. It uses classes as blueprints to create objects.

Class Components

A class typically includes:

  1. Fields (variables)
  2. Getters and Setters (accessors)
  3. Constructors (initialization)
  4. Methods (functions)

Class Structure Diagram

classDiagram
    class Employee {
        -String name
        +String emp_name
        +void set emp_name(String)
        +String get emp_name()
        +void result()
    }
    
    class Main {
        +void main()
    }
    
    Main ..> Employee : creates

Example: Employee Class

class Employee {
    String name;
    
    // Getter method
    String get emp_name {
        return name;
    }
    
    // Setter method
    void set emp_name(String name) {
        this.name = name;
    }
    
    // Function definition
    void result() {
        print(name);
    }
}
 
void main() {
    // Object creation
    Employee emp = new Employee();
    emp.name = "employee1";
    emp.result();  // Output: employee1
}

Explanation:

  • Employee: Class name
  • name: Field (instance variable)
  • emp_name: Getter and setter for the name field
  • result(): Method to print the employee name
  • new Employee(): Creates an instance of the Employee class

Lab Exercises

Exercise 1: Calculator

Write a Dart program that:

  1. Takes two numbers and an operator (+, -, *, /) as input
  2. Uses a switch statement to perform the operation
  3. Prints the result

Expected Output Example:

Enter first number: 10
Enter second number: 5
Enter operator (+, -, *, /): *
Result: 50

Exercise 2: FizzBuzz

Write a program that prints numbers from 1 to 20:

  • If the number is divisible by 3, print "Fizz"
  • If the number is divisible by 5, print "Buzz"
  • If divisible by both 3 and 5, print "FizzBuzz"
  • Otherwise, print the number

Expected Output:

1
2
Fizz
4
Buzz
Fizz
7
8
Fizz
Buzz
11
Fizz
13
14
FizzBuzz
...

Exercise 3: Student Management System

Create a Student class with the following:

  • Fields: name (String), id (int), gpa (double)
  • Method: isHonors() returns true if GPA >= 3.5
  • Method: displayInfo() prints student details

In the main() function:

  1. Create at least 3 student objects
  2. Display their information
  3. Print whether each student is an honors student

Exercise 4: Prime Number Checker

Write a function isPrime(int number) that:

  • Returns true if the number is prime
  • Returns false otherwise

Test your function with numbers: 2, 7, 15, 23, 30

Additional Resources

End of Lab 1