What are errors?

Errors are flaws in a program that causes the program's behavior to be aberrant, and even experienced developers can make these mistakes. Programming errors are often known as bugs or faults, and debugging is the act of eradicating them.

Types of errors

• Syntax errors.
• Runtime errors.
• Logical errors.
• Compilation errors.
• Arithmetic errors.

Syntax errors

Computer languages, like any other language, have grammar rules. However, people can communicate even with bad grammar, but computers are unable to ignore faults, such as syntax errors. Errors that occur in the program due to violation of the rules of the language are known as syntax errors. These errors are detected by the compiler which stops the execution of the program. Some examples include the use of erroneous punctuation and utilizing a variable(e.g. x,y, etc) that hasn't been initialized/declared.

The process of identifying and correcting syntax errors is quite simple. The compiler generates an error message to describe the cause and location of the error. The error usually happens on the compiler-specified line or the preceding line; however, if the problem involves incorrectly placed braces, an actual error may occur at the start of the built-in module. 

Runtime-errors

You might discover a Java bug while your application is running if there are syntax errors. You'll get an error notice that includes the type of issue as well as a stack trace that shows where and how the error occurred. If a runtime error occurs while running a program the code may run successfully on the computer, but it will not produce the expected results.

Runtime issues are particularly dangerous since they can have an immediate impact on the end-user. These issues arise while the technology is in use and may prohibit someone from achieving their objectives. Even when there are no logical mistakes and the program is successfully compiled, the program does not always yield the desired results. Inappropriate math operations and incorrect input data can cause these problems. 

Logical errors

A logical mistake occurs when the program compiles and executes yet does something incorrectly. It is the most difficult error to trace down. Although the software is technically valid, the results will not be what you intended. A logic error is an error in the source code of a program that causes unexpected and erroneous behavior. A logic mistake is a type of runtime fault that can cause a program to produce inaccurate information (output). It may also cause the program to crash while it is being used.

Logical problems aren't usually easy to spot right away. This is because, unlike syntax faults, such errors are correct when examined in the context of the language, but do not result in the desired behavior. Both interpreted and compiled languages can have these issues. A logical error is another name for a logic error. Because the Java system has no understanding of what your software is supposed to perform, it provides no extra information to assist you in locating the problem.

The following are some methods for locating a logical error:

• Consider what the program had to accomplish to achieve the results it did. This will bring you to the location where the error occurred.
• Put print statements in the program to figure out what it's doing.
• Step through your program with a debugger and observe what it accomplishes.

Arithmetic Errors

Arithmetic errors are similar to logic errors, except they involve mathematics. For example, dividing any number by 0 generates an error, such as writing 5 / 0. 

Compilation Errors

The compilation is necessary for several programming languages. The high-level language is converted into a lower-level language that the computer can understand better during compilation. When the compiler doesn't know how to convert the code to lower-level code, it produces a compile-time error. 

Handling the error

Error is a programming flaw, and there is nothing that can be done about it other than stepping in, modifying, and fixing it. However, your software must be designed so that it can handle this issue without causing any other fatal faults in the meanwhile. Error management is easy in small software, but it might be a waste of effort in huge software. At this point, error handling is transformed into exception handling.

Exception handling is similar to error handling, except that your code does not jump to an error state when a problem occurs. Rather, it interprets the problem as an exception and returns a preset response.

Fixing of errors

• Make a list of any exceptions. Depending on your program, these exceptions may cause difficulties with your data if they are not expressed appropriately.
• If possible, create your error hierarchy. Many languages provide exceptions and error handling classes. However, for readability and consistency, it is best to write your code.
• Avoid dealing with all exceptions. We don't want the program to fail, but attempting to run everything at once can waste time and make your code more difficult to manage. An exception can be handled at any point in the call stack.
• Check that the parentheses are appropriately aligned if a syntactic mistake occurs.
• Examine the code to see if all the variables are defined. Add a line of code to declare the variable if it hasn't been declared before using it.
• Check to see if there are any missing quotes. Check the quotes in the same way as you would the parentheses. Fix the problem and double-check that the code works.
• Look for any missing punctuation or spelling errors in the return statement.
• At the end of the statement, look for a missing semicolon. When writing code, get into the habit of using a semi-colon instead of a period after each sentence.

Importance of handling the error

The code will not be compiled if there is even a slight error. As a result, the developer will not be able to tell if their program is working, hence addressing the errors as soon as possible is essential. Error handling is critical because it makes it easier for your code's end users to use it properly. Another key benefit is that it makes it easy to maintain the code.

Context and Applications

This topic is important for postgraduate and undergraduate courses, particularly for, 

• Bachelors in Computer Science Engineering.
• Associate of Science in Computer Science.

Practice Problems

Question 1: Compiler can check _____ error.

1. Logical
2. Syntax
3. Content
4. Both A and B

Answer: Option 2 is correct.

Explanation: Syntax errors are mistakes in the source code, such as spelling and punctuation errors, incorrect labels, and so on, which cause an error message to be generated by the compiler.  However, syntax errors are the easiest to find and correct and the compiler will tell you where it got into trouble.

Question 2: When does a runtime error occur?

1. During compilation
2. After compilation
3. Before compilation
4. None of the above

Answer: Option 2 is correct.

Explanation: A runtime error in a program is an error that occurs while the program is running after being successfully compiled. Runtime errors are commonly called referred to as bugs and are often found during the debugging process before the software is released.

Question 3:  Logical errors can produce ___ output.

1. correct
2. incorrect
3. mathematical
4. None of these

Answer: Option 2 is correct.

Explanation: The logical error is an error that leads to an undesired output. These errors produce incorrect output, but they are error-free, and also known as logical errors. 

Question 4: Error is ________.

1. Null pointer
2. result
3. programming flaw
4. None of these

Answer: Option 3 is correct.

Explanation:  Error is a programming flaw, and there is nothing that can be done about it other than stepping in, modifying, and fixing it. Error management is easy in small software, but it might be a waste of effort in huge software. At this point, error handling is transformed into exception handling.

Question 5: _____ is called an error in a program.

1. Degbug
2. Bug
3. Virus
4. None of these

Answer: Option 2 is correct.

Explanation: If an error is found in the set of instructions given to the computer, it is called a bug.