Types of Errors in Programming

Last Updated on April 20, 2023 by Prepbytes

Errors in programming refer to issues or defects that arise within the program, resulting in abnormal behavior. Even experienced developers can make these mistakes, which are also referred to as bugs or faults. The process of eliminating these errors is called debugging. These errors in Programming can be identified during the program’s compilation or execution, and it’s crucial to remove them to ensure the program runs smoothly. Here we will discuss the various types of errors in programming and some of the common causes behind them. So, let’s dive straight into the topic of Types of Errors in Programming.

What are the Different Types of Errors in Programming?

As mentioned above errors refers to issues that occur in a program that results in unwanted behavior of the program. Some common Types of Errors in Programming are listed below.

• Syntax Error
• Run-Time Error
• Linker Error
• Logical Error
• Semantic Error

Let us discuss each of these types of errors in programming in detail.

Syntax Error

A syntax error is the most common type of error in programming. It occurs when the programmer writes code that is not in accordance with the syntax of the programming language. Syntax errors are detected by the compiler, and the compiler reports an error message to the programmer.

Common examples of syntax errors include,

• Forgetting to add a semicolon,
• Spelling a keyword incorrectly
• Missing a closing brace.

Example of Syntax Error
Here is an example code having a syntax error.

#include <iostream>
using namespace std;

int main() 
{
  cout << "Hello, world!"
  return 0;
}

Output:

prog.cpp: In function ‘int main()’:
prog.cpp:6:26: error: expected ‘;’ before ‘return’
   cout << "Hello, world!"
                          ^
                          ;
   return 0;
   ~~~~~~                 

Explanation:
In the above example, the programmer forgot to add a semicolon after the cout statement, resulting in a syntax error as shown in the output.

Run-time Error

A run-time error occurs during the execution of a program. These errors occur when a program tries to perform an illegal operation, such as dividing by zero or attempting to access an invalid memory address. The program compiles without errors, but when it runs, it encounters an error that causes it to terminate abnormally. Run-time errors are often difficult to detect because they do not show up until the program is executed.

Example of Run-Time Error
Let us see a C++ code that throws a runtime error.

#include <iostream>
using namespace std;

int main() 
{
  int a = 5, b = 0;
  int c = a / b;
  cout << "The result is " << c;
  return 0;
}

Output:

Runtime error #stdin #stdout

Explanation:
In the above example, the program tries to divide a by b, which is zero. Since division by zero is undefined, the program will stop abruptly and we don’t get any output on the screen as this results in the runtime error.

Linker Error

A linker error occurs when a program references a function or variable that is not defined in the program or the libraries it is linked against. Linker errors typically occur when a program is compiled and linked. The linker will report an error if it cannot find the necessary files or libraries to link the program.

Example of Linker Error
Here is the code that will show the linker error.

#include <iostream>
using namespace std;

int main() 
{
  cout << "Hello, world!" << endl;
  myFunction();
  return 0;
}

Output:

prog.cpp: In function ‘int main()’:
prog.cpp:7:3: error: ‘myFunction’ was not declared in this scope
   myFunction();
   ^~~~~~~~~~

Explanation:
In the above code, we call the function named as myFunction(), but the function is not defined in the program or any of its libraries. As soon as we compile the program, the linker reports the error “myFunction() is undefined” on the output screen.

Logical Error
A logical error occurs when the program compiles and runs without any syntax, run-time, or linker errors, but the output is incorrect. These errors occur when the program's logic or algorithms are incorrect. Logical errors are challenging to detect because the program does not generate any error messages.

Example of Logical Error
Let us understand this error with the help of an example.

#include <iostream>
using namespace std;

int main() {
  int a = 5, b = 7;
  
  if (a > b) {
    cout << "a is less than b";
  } else {
    cout << "b is less than a";
  }
  return 0;
}

Output:

b is less than a

Explanation:
In the above example, the program intends to check if a is less than b. However, the program checks if a is greater than b, resulting in incorrect output. The logic for checking the smaller number is wrong because of the usage of the ‘>’ sign instead of ‘<’.

Semantic Error

Semantic errors are errors that occur when the code written by the programmer makes no sense to the compiler, even though it is syntactically correct. They are different from syntax errors, which indicate errors in the structure of the program, as semantic errors are related to the meaning and implementation of the program.

For example,

• Using a string instead of an integer or accessing an array index that is out of bounds can cause semantic errors.
• Uninitialized variables and type incompatibility are other common types of semantic errors.

Example of Semantic Error
Here is the code for a better understanding of Semantic Errors in Programming.

#include <iostream>

int main() {
    int a, b, c;
    
    a * b = c;
    // This will generate a semantic error
    
    return 0;
}

Output:

prog.cpp: In function ‘int main()’:
prog.cpp:6:13: error: lvalue required as left operand of assignment
     a * b = c;
             ^

Explanation:
Here in this example, we get a semantic error because when an expression is placed on the left side of an assignment operator (=), it can cause a semantic error even if the code is written correctly according to syntax rules. This is because the compiler cannot interpret the code correctly, leading to errors in program execution.

Conclusion
In conclusion, programming is a complex task that requires a high level of attention to detail. Errors can occur at various stages of the programming process. There are different types of errors in programming including syntax errors, run-time errors, linker errors, logical errors, and semantic errors. Syntax errors are the most common type of error, while run-time errors are often the most challenging to detect. Linker errors occur during the compilation and linking process, while logical errors and semantic errors occur when the program's algorithms or requirements are misunderstood.

Frequently Asked Questions(FAQs)

Here are some Frequently Asked Questions on Types of Errors in Programming.

Ques 1. How do you fix a syntax error in Programming?
Ans. Syntax errors can be fixed by identifying the incorrect syntax and correcting it. Most of the time these are identified by the IDEs.

Ques 2. How do you fix a runtime error?
Ans. Runtime errors can be fixed by identifying the cause of the error and modifying the code to handle it correctly.

Ques 3. What is a divide-by-zero error?
Ans. A divide-by-zero error occurs when a program tries to divide a number by zero, which is not a valid mathematical operation.

Ques 4. What is an index out-of-bounds error?
Ans. An index out-of-bounds error occurs when a program tries to access an array element with an index that is outside the bounds of the array.