Lesson 3: Basic Syntax and Data Types in C

Welcome to Lesson 3! In this lesson, we’ll explore the basic syntax of C# and introduce you to its data types. Understanding the syntax and data types is crucial for writing effective and error-free code.

1. Basic Syntax

C# syntax is designed to be clean and readable. Here are some fundamental syntax elements you’ll encounter:

1.1. Comments

• Single-line comments: Start with //. They extend to the end of the line.

  // This is a single-line comment

• Multi-line comments: Enclosed between /* and */.

  /*
    This is a multi-line comment
    It can span multiple lines
  */

1.2. Statements and Semicolons

• Each statement in C# ends with a semicolon (;).

  int number = 10; // This is a statement

1.3. Blocks of Code

• Code blocks are enclosed in curly braces {}.

  class Program
  {
      static void Main()
      {
          // Code inside Main method
      }
  }

1.4. Indentation and Formatting

• Indentation helps make the code more readable. It’s a good practice to use consistent indentation (typically 4 spaces or a tab) to structure your code properly.

2. Data Types

C# supports various data types, which can be broadly classified into value types and reference types. Here’s a closer look at the most commonly used data types:

2.1. Value Types

• Value types store data directly and are usually stack-allocated. They include: 2.1.1. Integers
• int: 32-bit signed integer
  csharp int age = 30;
• long: 64-bit signed integer long distance = 123456789L; 2.1.2. Floating-Point Numbers
• float: Single-precision floating-point number
  csharp float temperature = 98.6f;
• double: Double-precision floating-point number double pi = 3.14159; 2.1.3. Decimal
• decimal: 128-bit precise decimal value, useful for financial calculations decimal price = 19.95m; 2.1.4. Characters and Boolean
• char: Single 16-bit Unicode character
  csharp char initial = 'A';
• bool: Represents a Boolean value (true or false)
  csharp bool isCSharpFun = true;

2.2. Reference Types

• Reference types store references to objects and are typically heap-allocated. They include: 2.2.1. Strings
• string: Represents a sequence of characters string greeting = "Hello, World!"; 2.2.2. Objects
• object: The base type from which all other types derive; can hold any data type
  csharp object anything = "Can be anything"; anything = 12345; // Now holding an integer

3. Type Conversion

You often need to convert between different data types. C# supports both implicit and explicit type conversions:

3.1. Implicit Conversion

• Automatic conversion by the compiler from a smaller type to a larger type (e.g., from int to double).

  int a = 10;
  double b = a; // Implicit conversion

3.2. Explicit Conversion

• Requires a cast when converting from a larger type to a smaller type or between incompatible types.

  double x = 9.78;
  int y = (int)x; // Explicit conversion

3.3. Using Convert Class

• The Convert class provides methods for converting between base types.

  string numberString = "123";
  int number = Convert.ToInt32(numberString);

4. Variable Declaration and Initialization

In C#, you declare variables to store data, and you can initialize them at the time of declaration:

4.1. Declaring Variables

• To declare a variable, specify the data type followed by the variable name.

  int age;
  float height;

4.2. Initializing Variables

• You can initialize a variable when declaring it.

  int age = 25;
  float height = 5.9f;

5. Example: Combining Syntax and Data Types

Here’s a complete example that demonstrates basic syntax and data types in a C# program:

Code Example:

using System;

class Program
{
    static void Main()
    {
        // Variable declarations and initializations
        int numberOfStudents = 30;
        double averageScore = 85.5;
        string courseName = "Introduction to C#";
        bool isPassed = true;

        // Output to the console
        Console.WriteLine("Course: " + courseName);
        Console.WriteLine("Number of Students: " + numberOfStudents);
        Console.WriteLine("Average Score: " + averageScore);
        Console.WriteLine("Passed: " + isPassed);
    }
}

Explanation:

• We declare variables of various types, initialize them, and then use Console.WriteLine to print their values to the console.

Summary

In this lesson, you learned about the basic syntax of C# and its data types. Understanding these fundamentals is essential for writing effective C# code. We covered variable declarations, data types, type conversions, and how to use these in a simple program.

Happy coding!