Common Types Of Errors

Lesson 4.1: Common Types of Errors

Errors are an inevitable part of programming. Learning to identify and fix errors is a crucial skill for any C# developer. In this lesson, you'll learn about three main categories of errors: syntax errors, runtime errors, and logical errors.

1. Syntax Errors

What Are They? Syntax errors are violations of the C# language's grammatical rules. They occur when you write code that doesn't follow the correct structure or spelling.

Examples:

Missing semicolons (;) at the end of statements.

Misspelled keywords (e.g., whiel instead of while).

Unmatched parentheses or curly braces.

When They Happen: The compiler catches syntax errors while trying to translate your code.

How to Spot Them: Visual Studio (or your code editor) will usually underline the problematic code with a red squiggly line and provide error messages.

C#

// Example Syntax Error

int x = 5 

Console.WriteLine(x); // Missing semicolon

2. Runtime Errors (Exceptions)

What Are They? Runtime errors occur while your program is executing. They arise when your code attempts an operation that's impossible or invalid at that moment.

Examples:

Dividing by zero.

Trying to access an array element that doesn't exist.

Reading from a file that doesn't exist.

When They Happen: Runtime errors cause your program to crash or throw an exception (a special object indicating an error).

How to Spot Them: Visual Studio's debugger can help you pinpoint the exact line of code where the error occurs. You'll often see a detailed error message in the console.

C#

// Example Runtime Error

int[] numbers = { 1, 2, 3 };

int result = numbers[5]; // IndexOutOfRangeException: Index was outside the bounds of the array.

3. Logical Errors

What Are They? Logical errors are mistakes in your program's algorithm or the way you've structured your code. The code might compile and run without crashing, but it doesn't produce the correct results.

Examples:

Incorrect calculations.

Loops that don't terminate when they should.

Conditions that aren't evaluated correctly.

When They Happen: Logical errors are the trickiest to spot because they don't cause obvious crashes. They can only be found by carefully testing and analyzing your code's output.

How to Spot Them: Debugging tools like Visual Studio's debugger can help you trace the flow of your program and inspect variable values to find the root of the problem.

C#

// Example Logical Error

int x = 5;

int y = 10;

int sum = x - y; // The sum should be x + y

Tips for Dealing with Errors

Read Error Messages Carefully: They often provide valuable clues about what went wrong.

Use the Debugger: The debugger is your friend! Learn how to use breakpoints, step through code, and examine variables to find errors.

Test Thoroughly: Write test cases to ensure your code works as expected under various conditions.

Don't Panic! Errors are a normal part of programming. Learn from your mistakes and become a better programmer.

This is a basic overview of common errors in C#.  In the next lessons, you'll learn about more advanced error handling techniques, such as using try-catch blocks to gracefully handle exceptions.

Course Syllabus