• +91-9142290450

  • Hajipur, Bihar, 844101

☰
❮
❯

C++ Errors

← Previous Next →

Errors are an unavoidable part of programming. Every programmer encounters them while writing or running code. In C++, errors can appear when the compiler finds something wrong in the code, or when the program behaves unexpectedly while running. Understanding different types of errors helps you write cleaner, bug-free programs and fix issues quickly.

In this tutorial, we’ll go through what errors are, their types, examples of each, and some tips to handle them effectively.

What Is an Error in C++?

An error is a problem that prevents your program from compiling or running correctly. Some errors occur before the program runs (compile-time errors), while others happen during execution (runtime errors).

C++ provides several tools and features to detect, prevent, and handle these errors to make programs more reliable.

Types of Errors in C++

Errors in C++ are generally divided into four major categories:

  1. Syntax Errors

  2. Logical Errors

  3. Runtime Errors

  4. Semantic Errors

Let’s understand each of these with examples.

Syntax Errors

Syntax errors occur when the code violates the grammatical rules of the C++ language. The compiler detects these errors before the program is executed.

Example:

#include <iostream>
using namespace std;

int main() {
    cout << "Hello World"   // Missing semicolon
    return 0;
}

The compiler will show an error because of the missing semicolon after the cout statement.

Common Causes of Syntax Errors:

  • Missing semicolons or brackets

  • Incorrect variable declarations

  • Misspelled keywords or functions

  • Wrong usage of operators

These are usually easy to fix since the compiler highlights the exact line of the problem.

Logical Errors

Logical errors occur when the program runs successfully but gives the wrong output. The syntax is correct, but the logic behind the code is flawed.

Example:

#include <iostream>
using namespace std;

int main() {
    int a = 5, b = 10;
    cout << "Average: " << (a + b / 2);
    return 0;
}

Here, the result will not be the correct average because the expression is evaluated as a + (b / 2) instead of (a + b) / 2.

How to Fix Logical Errors:

  • Use debugging tools to check variable values.

  • Add print statements to trace the program’s behavior.

  • Test your logic with different inputs.

Runtime Errors

Runtime errors occur when the program compiles successfully but fails during execution. These errors usually happen due to invalid user input, memory issues, or mathematical mistakes like dividing by zero.

Example:

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 0;
    cout << "Result: " << a / b;
    return 0;
}

This program will compile, but when executed, it will cause a division by zero error.

Common Causes of Runtime Errors:

  • Dividing by zero

  • Accessing invalid array indexes

  • Insufficient memory allocation

  • File handling issues

  • Null pointer dereferencing

Semantic Errors

Semantic errors occur when the meaning of the code is incorrect even though it is syntactically valid. These errors happen when the program does something different from what you intended.

Example:

#include <iostream>
using namespace std;

int main() {
    int x = 10;
    cout << "The square is: " << x * 3; // Intended to square, but multiplied by 3
    return 0;
}

The code runs fine, but it gives the wrong output because the logic does not match the intended meaning.

Linker Errors

Linker errors occur when the compiler finds all source code files but cannot correctly link them together into a single executable program.

Example:

#include <iostream>
using namespace std;

void display(); // Function declared but not defined

int main() {
    display();
    return 0;
}

If the function display() is never defined, the linker will show an error because it cannot find the function implementation.

Common Causes of Linker Errors:

  • Missing function definitions

  • Incorrect library linking

  • Multiple definitions of the same function

Logical vs Runtime Errors

Type Detected By Occurs When Example
Logical Programmer Wrong logic used Wrong output but no crash
Runtime System Program executes invalid operation Division by zero

Understanding the difference helps you decide whether the problem lies in your logic or in program execution.

Common Compiler Error Messages

Some common error messages you might see include:

  • Syntax error: missing ';' before 'return'

  • Undefined reference to function

  • Segmentation fault

  • Expected '}' at end of input

  • Cannot convert 'int*' to 'char*'

Reading and understanding these messages is key to debugging effectively.

Tips to Avoid and Fix Errors

  1. Write and test code in small sections – Avoid writing long blocks of code without testing.

  2. Use meaningful variable names – It helps track logic errors easily.

  3. Use comments – Explain complex logic for future debugging.

  4. Enable compiler warnings – They can catch potential problems early.

  5. Always check input and memory usage – Prevent runtime errors like invalid inputs or buffer overflows.

Summary of C++ Errors

Errors are part of every programming journey. In C++, they can occur at different stages such as compilation, linking, or execution. The main types include syntax, logical, runtime, and semantic errors. By understanding how these errors arise and how to fix them, you can write cleaner, more reliable code. Debugging tools, meaningful testing, and careful code structure make it easier to detect and resolve errors efficiently.

Practice Questions

  1. Write a program with a missing semicolon and observe the compiler error message.

  2. Create a C++ program that divides two integers. Try entering 0 as the denominator and note what happens.

  3. Write a program that uses a variable before declaring it. Identify the error message shown by the compiler.

  4. Make a program that calculates the area of a circle but forgets to include <cmath> while using the pow() function. See what linker error occurs.

  5. Write a simple addition program but intentionally use subtraction instead. Identify it as a logical error.

  6. Create a function declaration without defining it. Compile and check for linker errors.

  7. Write a program that tries to access an array element outside its valid index range. Observe the runtime error.

  8. Remove a closing bracket } from a small C++ program and see how the compiler responds.

  9. Write a program where a pointer is not initialized but still dereferenced. Identify the runtime error caused.

  10. Create a program that prints the result of dividing two integers but uses integer division instead of float division. Recognize it as a logic-based mistake.

← Previous Next →

Try a Short Quiz.

coding learning websites codepractice

No quizzes available.

CPP Programming

online coding class codepractice

Introduction to C++

C++ Basics

Control Flow

Collections & Memory

Functions

Object-Oriented Programming

File Handling & Date

Error Handling & Validation

STL & Data Structures

Namespaces

codepractice logo
Login
Go Back Top