Difference Between Syntax Error and Logical Error

Key Difference – Syntax Error vs Logical Error
 

When programming, there can be errors. An error is an unexpected output of the program. These errors can affect the proper execution of the program. Therefore, it is necessary to remove all errors. An error is also called as a bug. The process of identifying errors and fixing them is called debugging. Each programming language has a specific syntax. The programmer should follow the correct syntax to write programs. When there is syntax mistake, it is known as a syntax error. A syntax error occurs at compile time. The error that occurs at runtime is called a runtime error. Array out of bound, diving by zero, accessing memory that is not available are some examples of runtime errors. When writing a program, there is a sequence of steps to follow to solve the problem. This methodology is called an algorithm. If the logic of the program is wrong, it will give incorrect output.  That kind of an error is known as a logical error. This article discusses the difference between a syntax error and a logical error. The key difference between syntax error and logical error is that, the syntax error occurs due to an error in the syntax of a sequence of characters or tokens that is intended to be written in a particular programming language while logical error is an error that occurs due to the fault in the program algorithm or the logic.

CONTENTS

1. Overview and Key Difference
2. What is Syntax Error
3. What is Logical Error
4. Similarities Between Syntax Error and Logical Error
5. Side by Side Comparison – Syntax Error vs Logical Error in Tabular Form
6. Summary

What is Syntax Error?

Generally, the programs are written using high-level programming languages. C, Python, Java are some examples of high-level programming languages. The source code is easy to read and understandable by humans. These programs are not understandable by the computer. The computer only understands machine code. Therefore, the high-level program is converted into machine code using a compiler. Each programming language has own set of syntax to write the program. The programmer should write the program according to the correct syntax. If not, it will cause an error. This error type is known as a syntax error. This error occurrs at the time of compilation.

It is easy to identify and remove syntax errors because the compiler displays the location and type of error. When there are syntax errors, the source code will not have translated into the machine code. Therefore, for successful execution, the programmer should fix the syntax error specified by the compiler. Some common examples of syntax errors are missing semicolons, missing curly braces, undeclared variables or misspelled keywords or identifiers. If the programmer only writer int x without the semicolon, it is a syntax error. Misspelling the ‘int’ is a syntax error. Therefore, it is necessary to follow the syntax relevant to the programming language when writing the program. The program will not compile until the syntax error is fixed. In an interpreted language, a syntax error is detected during program execution, so it might be harder to differentiate syntax errors from other errors.

What is Logical Error?

A program is written to solve a problem. Therefore, it flows an algorithm to solve it. An algorithm is a step by step procedure to solve a given problem. The errors occur due to an algorithm fault is known as a logical error. A program with logical error will not cause the program to terminate the execution but the generated output is wrong. When a syntax error occurred, it is easy to detect the error because the compile specifies about error type and the line that the error occurs. But identifying a logical error is hard because there is no compiler message. The output is wrong, even the program executed. Therefore, the programmer should read each statement and identify the error on his own. One example of logical error is the wrong use of operators. If the programmer used division (/) operator instead of multiplication (*), then it is a logical error.

What is the Similarity Between Syntax Error and Logical Error?

• Both Syntax Error and Logical Error are categories of errors in programming.

What is the Difference Between Syntax Error and Logical Error?

Summary – Syntax Error vs Logical Error

Errors might occur while programming. There are different types of errors. Runtime error occurs at runtime. Some examples of runtime errors are diving by zero, accessing memory that is not available. Syntax errors occur due to syntax mistakes. The logical errors occur due to a fault in the logic of the program. The difference between a syntax error and logical error is that the syntax error occurs due to an error in the syntax of a sequence of characters or tokens that is intended to be written in a particular programming language while a logical error is an error that occurs due to the fault in the program.

Reference:

1.PGC Lectures: Programming Errors & Types, Syntax Error, Runtime Error, Logical Error, Online Learners, 8 Jan. 2017. Available here  
2.“Syntax error.” Wikipedia, Wikimedia Foundation, 17 Feb. 2018. Available here
3.“Logic error.” Wikipedia, Wikimedia Foundation, 27 Feb. 2018. Available here