The idea of “exception handling” is used in algorithms to deal with errors that might happen during runtime and stop a program from working normally. Some of the errors which can be handled using this concept are:
The good thing about this implementation is that it keeps the program from crashing if there is an error while it is running. The program will throw an error if it runs into an exception without exception handling, and the rest of the program will not be run. Implementing this idea, on the other hand, will provide a way around the problem so that the remaining parts of the program can be run as long as they are not affected by the exception. To learn more, check out our data science courses.
To understand why interview questions about Java exception handling come up so often, you need to know how important the subject is.
Minute errors from the developer’s side can significantly hamper the flow of data. For instance, if there are eight statements in a row and the fourth one is wrong, the rest of the statements will not be run. Exception handling, on the other hand, will make sure that all statements are run except the one that fails. This is why knowing and using exception handling is so important.
Exceptions can happen for a number of reasons, such as bad user input, losing the network connection, coding mistakes, the disk running out of memory, any kind of device failure, and so on. so there is a good chance that errors or exceptions will happen. This is why Java exception handling interview questions are pretty common in all developer jobs. So, make sure to prepare for these Java exception handling interview questions by clarifying concepts.
It’s common for interviewers to ask about getting exception handling in Java, which makes it even more important to prepare. Questionnaires about exception handling in Java help the recruiter figure out how much the candidate knows and whether they can handle any bad situations that might happen, like a program crashing or requests failing.
Here is a list of good interview questions about how to handle exceptions in Java that will help you get that dream job.
As a programmer, few things induce panic like seeing a sea of red squiggly lines light up your IDE Compiler errors – the inevitable speed bumps on the coding highway. While frustrating, wrestling with these cryptic messages is a rite of passage for developers Mastering the skill of debugging compiler errors also provides valuable insights into the inner workings of programming languages.
In technical interviews, expect questions that test your understanding of common compile-time issues. Whether you’re an aspiring new grad or a seasoned professional, knowing how to analyze, troubleshoot and resolve compiler errors is a must-have skill.
This comprehensive guide presents the top 25 compiler error interview questions that you should prepare for Let’s dive in!
1. What is a compiler error and what are the main types?
A compiler error occurs when source code violates the syntax or semantic rules of a programming language, preventing successful translation into machine code. The three main categories are:
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Syntax errors – related to grammar mistakes like unclosed brackets or missing semicolons
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Semantic errors – logically incorrect code that is syntactically valid, like type mismatches or undeclared variables.
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Linker errors – issues combining separate compiled code, e.g undefined symbols.
Identifying the error type helps narrow down causes during debugging.
2. How are compiler errors different from runtime errors?
While both indicate problems in code, compiler errors prevent generation of an executable program while runtime errors allow compilation but cause unexpected behavior during execution.
For example, a syntax error like a missing bracket will generate a compiler error. But attempting to access an out-of-bounds array element would compile just fine and only throw a runtime error when that code executes.
3. Walk me through how you would debug a compiler error.
When faced with a compiler error, I follow these steps:
- Examine the error message for clues on the issue type and location.
- Isolate the problematic code section.
- Trace through code logic to identify probable causes.
- Consult documentation for related errors.
- Try fixes like adding declarations or tweaking syntax.
- Recompile after each change to check if issue resolves.
- Use debugging tools to step through code execution if needed.
- Ask colleagues for inputs if stuck.
The key is methodically narrowing down the cause through analysis, research and trial-and-error.
4. What’s the difference between a linker error and compiler error?
Compiler errors arise during compilation of individual source code files due to issues like syntax mistakes, type violations etc.
Linker errors occur during the linking phase when the compiler tries to combine compiled object files into an executable. Common causes include missing function declarations or duplicate symbol definitions across source files.
While compiler errors prevent generating an object file itself, linker errors prevent generating the final executable even if individual files compiled properly.
5. You get a type mismatch error. What are some ways to investigate and fix this?
When encountering a type mismatch error, I would:
- Examine the line causing the error and analyze the data types of variables involved
- Check where the variables are declared to confirm their intended types
- Assess if an unacceptable implicit conversion is occurring like int to string
- Consider adding explicit casting like parseInt() for string to int conversion
- Change variable types if necessary to maintain compatibility
- Recompile after each change to see if the error persists
The goal is to trace the flow and rectify any discrepancies between data types used.
6. How might memory leaks occur in compiled languages?
Memory leaks happen when allocated memory isn’t released after use, gradually reducing available memory. Common causes in compiled languages:
- Forgetting to deallocate dynamic memory via delete or free()
- Losing reference to heap objects before garbage collection can release it
- Errors preventing deallocation code from executing like exceptions
- Bugs in data structure implementation causing duplicate references
Languages like C/C++ require manual memory management and are prone to such issues if allocations/deallocations are unbalanced.
7. You get a variable scope error in C++. How do you respond?
I would:
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Identify where the variable is declared to determine its scope – local, global etc.
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Check where it is being accessed and if scope rules are being violated.
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Consider expanding scope by declaring variable globally or passing as a function parameter.
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For function local variables, ensure no use outside the function body.
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Recompile after modifying scope to confirm issue resolution.
The key is aligning declaration and access to variables within permitted scope, or modifying scope as needed.
8. What causes array index out of bound errors and how can you prevent them?
Attempting to access elements at invalid indices outside the array size leads to these errors. Common causes are loop termination conditions exceeding array bounds or hard-coded indices blindly assuming array size.
Ways to prevent:
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Use array length properties to determine valid indices
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Validate indices before array access e.g. if (index < arr.length)
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Avoid hard-coded indices and Loop within array size
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Use foreach constructs instead of manual index incrementing
Proper validation and avoidance of assumptions about array size can eliminate such errors.
9. When might you get a null reference error in compilation?
Attempting to access members or methods on a variable referencing null rather than an initialized object will lead to null reference compiler errors in languages like Java and C#.
Common cases include:
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Forgetting to instantiate an object before use
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Explicitly assigning null but still using the variable
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Function intended to return an object but returns null instead
Careful initialization of objects and null checking before dereferences can prevent this.
10. You are getting template instantiation errors in C++. What do you do?
For errors instantiating class or function templates in C++:
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Check template parameter types used match declared parameters
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Ensure correct number of parameters passed to template
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Declare specializations for troublesome types
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Include template definitions in header files if linker error
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Use ‘export’ with explicit template instantiations
Verifying template usage as per specifications and providing specializations can resolve such errors.
11. Have you debugged ambiguous method call errors before? How?
Yes, these occur when compiler cannot disambiguate between methods with similar signatures. To resolve:
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Identify conflicting methods with similar parameters
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Make call explicit by specifying argument types
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Rename methods to improve distinction
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Refactor code to avoid method signature overlap
The key is isolating ambiguity and improving distinction through specificity and design.
12. What causes type casting errors during compilation? How can you avoid them?
Attempting to convert between incompatible types like string to integer can lead to casting errors. Ways to avoid:
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Use language-provided casting functions like parseInt()
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Add error handling code e.g. try-catch blocks
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Avoid assumptions about data types
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Declare variables and parameters with precise types
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Use temporary variables as intermediate step for multi-stage casts
Understanding language casting rules and having robust input validation can prevent such errors.
13. You are getting infinite recursion errors. How do you debug this?
I use the following techniques:
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Add logging statements to trace function entry
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Use debugger or IDE stack trace to analyze call sequence
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Identify conditions causing recursive instead of iterative behavior
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Check for missing or faulty base case leading to endless recursion
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Refactor code to optimize tail recursion if supported
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Modify design to use iterative logic over recursion where possible
Methodically following the recursion trail and introducing base cases is key to resolving these errors.
14. What might cause classpath issues during Java compilation?
The Java compiler needs to locate user-defined classes referenced in code. Classpath issues arise if:
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Classpath environment variable is incorrectly set
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Relative paths are used improperly for the file system
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Class file moved from location compiler is expecting
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Class name does not match file location and package hierarchy
Correctly configuring the classpath variable to indicate location of class files can prevent such errors.
15. You are facing thread synchronization issues in compilation. How do you tackle this?
I use the following strategies:
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Introduce locks/mutexes to ensure only one thread accesses shared resources
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Use semaphores for controlling concurrent access
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Leverage condition variables for signaling between threads
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Avoid race conditions through careful analysis and design
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Detect deadlock risks and introduce mitigation logic
Applying concurrency mechanisms methodically and testing rigorously are key to avoiding synchronization errors.
16. Can you share an example where you had to rethink your code structure due to a compiler error?
Recently when writing C++ code involving inheritance, I encountered issues due to multiple inheritance leading to diamond problem.
To resolve, instead of reliance on complex multi-parent hierarchies, I refactored my code using:
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Composition over inheritance principle
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Interfaces for abstraction without inheritance
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Virtual inheritance
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3. Is it possible to keep other statements in between ‘try’, ‘catch’, and ‘finally’ blocks?
Putting any statements in between the ‘try’, ‘catch’, and ‘finally’ blocks is not a good idea because they work together as a single unit to handle errors.
//Code which is monitored for exceptions.
//You can’t keep statements here
//Catch the exceptions thrown by try block, if any.
//You can’t keep statements here
//This block is always executed irrespective of exceptions.
4. Will it be possible to only include a ‘try’ block without the ‘catch’ and ‘finally’ blocks?
This would give a compilation error. It is necessary for either a “catch” block or a “finally” block to come after the “try” block, but not both. Either one of ‘catch’ or ‘finally’ blocks is needed so that the flow of exception handling is undisrupted.
The reason catch and finally sections are needed goes along with the whole point of exceptions: to deal with and respond to strange situations by taking control flow away from the usual “happy path.” So just watching for exceptions via try without defining mitigation steps makes little sense in isolation.
Either a catch block needs to be set up to handle the exception in some way, like logging it, showing an error message, or something else. Or, a final block should be specified for any cleanup routines that must execute regardless of specific exceptions. Without one of these recovery blocks present, any raised exception would go entirely unaddressed.
Exception handling tricky questions:
Aside from simple Java exception handling interview questions, you may also have to answer some tricky exception handling questions. Below are examples of such.
14. Does the ‘finally’ block get executed if either of ‘try’ or ‘catch’ blocks return the control?
No matter whether the try or catch blocks return control or not, the “finally” block is always run.
The last steps still happen whether the try block runs all the way through or has an early return statement in the middle. And whether exceptions are raised and control goes straight to different catch blocks, or whether no exceptions are raised at all, the final logic starts right away. Any manner of early control transfer or return calls cannot override or bypass invoking the final tasks.
This promise makes sure that things like unlocking external resources that were locked during the try block and saving data always get done.
15. Is it possible to throw an exception manually? If yes, explain how.
It is possible to throw an exception manually. It is done using the ‘throw’ keyword. The syntax for throwing an exception manually is.
Here is an example of using the ‘throw’ keyword to throw an exception manually.
NumberFormatException ex = new NumberFormatException(); //Here we create an object for NumberFormatException explicitly
throw ex; //throwing NumberFormatException object explicitly using throw keyword
System.out.println(“In this block, the explicitly thrown NumberFormatException object can be caught.”);
16. What do you mean by rethrowing an exception in Java?
The exceptions which are raised in the ‘try’ block are handled in the ‘catch’ block. This block can try to handle the exception again if the “catch” block fails. It can do this by using the “throw” keyword. This mechanism is called rethrowing an exception. The implementation is as follows:
String s = null;
System.out.println(s.length()); //This statement throws a NullPointerException
System.out.println(“Here the NullPointerException is caught”);
throw ex; //Rethrowing the NullPointerException
17. Why do you use the ‘throws’ keyword in Java?
If a method can throw an exception if it can’t be handled, it should add the “throws” keyword to describe that exception. It will be helpful to the caller functions of that method in handling that exception. The syntax for using the ‘throws’ keyword is,.
return_type method_name(parameter_list) throws exception_list
Here, exception_list is the list of exceptions which may be thrown by the method. These exceptions should be separated by commas. An example of the code :
public static void main(String[] args)
System.out.println(“NullPointerException thrown by methodWithThrows() method will be caught here”);
static void methodWithThrows() throws NullPointerException
String s = null;
System.out.println(s.length()); //This statement throws NullPointerException
18. It is often recommended to keep clean up operations like closing the DB resources inside the ‘finally’ block. Why is it necessary? .
No matter if exceptions are raised in the “try” block or caught in the “catch” block, the “finally” block is always run. These operations will always work as planned if you keep them in the “finally” block. Exceptions, which may or may not happen, will not affect them.
19. How would you differentiate between final, finally and finalize in Java?
In the first place, the keyword “final” can be used to make a variable, method, or class that can’t be changed. In other words, if you declare a variable as final, you can’t change its value after it has been set. If a method is declared as final, it cannot be overridden or modified in the sub class. If a class is declared as final, it cannot be extended into further classes.
Second, ‘finally’ is a block which is used in exception handling along with the ‘try’ and ‘catch’ blocks. This block is always executed irrespective of a raised exception or if the raised exception is handled. Most of the time, this block is used to close resources like database connections, I/O resources, and so on.
Third, the finalize() method is a protected method. It belongs to java. lang. Object class. Every class created in Java inherits this method. The garbage collector thread calls this method before an object is removed from the memory. This method is used to do some clean-up work on an object before it is deleted from memory.
protected void finalize() throws Throwable
20. What are customized exceptions in java?
Exception classes can be thrown in Java as per the requirements of the program flow. These exceptions are called user-defined exceptions. They are also called customized exceptions. These exceptions must extend any one of the classes in the exceptions’ hierarchy.
To give you an example of how to handle exceptions in Python or Java, an e-commerce system might create its own OrderValueException or ProductInventoryException classes that are specifically designed to work with its specific business needs. When compared to general exceptions like IllegalArgumentException, which could come from anywhere inside the application, the custom hierarchy makes domain issues easier to read.
Defining these domain-specific subclasses follows a similar process to building any class in Java. One only needs to extend an Exception or a child-like RuntimeException, give it the right class properties, and add constructors and methods for gathering information about the exception.
21. How would you explain a ClassCastException in Java?
When Java code tries to convert or cast an object of one class type to another class type that doesn’t work with it, a ClassCastException is thrown. In Java, objects have a defined class or type that tells you how they are structured and what methods they can use. This means that arbitrary casts between two different class types could fail because of the differences. This exception is thrown when the JVM can’t change an object from one type to another. It is a RunTimeException.
To avoid this error, knowing about assignable types and checking with instanceof statements are two ways to make sure that true object compatibility is checked instead of reference compatibility, which is not as strict. Additionally, minimising unnecessary casts by leveraging polymorphism or creating clean extension hierarchies prevents potential mismatches.
22. Differentiate between throw, throws and throwable in Java.
First, the keyword ‘throw’ is used to throw an exception manually in Java. Using this keyword, it is possible to throw an exception from any method or block. However, it is essential that the exception must be of type java. lang. Throwable class or it belongs to one of the sub classes of java. lang. Throwable class.
Second, the keyword ‘throws’ is used in the method signature in Java. If the method is capable of throwing exceptions, it is indicated by this method. The mentioned exceptions are handled by their respective caller functions. It is done either by using try and catch blocks or by using the throws keyword.
Third, the super class for all types of errors and exceptions in Java is called Throwable. It is a member of the java. lang package. The JVM or the throw statement raises only instances of this class or its subclasses. The catch block should contain only one argument and it should be of this type or its subclasses. In case customized exceptions are created, they should extend this class too.
23. Explain the StackOverflowError in Java.
This is an error that is thrown by the JVM when the stack overflows in runtime. The stack keeps track of method calls and local variables as the code goes deeper and deeper into nested method calls. As more methods run, more stack space gets consumed until it fills up completely.
This most commonly happens with recursive logic that perpetually invokes itself repeatedly without an adequate termination condition. With each stacked call added, the total footprint grows until hitting enviable capacity limits. Infinitely, recursing code is a prime offender. This error can also happen in very long-running processes that make a very long chain of method calls through many layers and into pipeline execution. Hundreds of activations pile up, draining stack reserves.
24. Is it possible for a subclass to add checked exceptions to a method in the superclass that throws an unchecked exception?
That’s not possible because if a method in the superclass throws an unchecked exception, the subclass will just copy it and throw the same or a different unchecked exception. But, it can not be overridden with checked exceptions. If a method is overridden, it must follow the same throws clause as its parent implementation when handling exceptions.
The reason lies in avoiding confusion for code that leverages polymorphism. If a superclass method could throw, say, an ArithmeticException but the subclass changed it to throw an IOException, any client code that was trying to catch the ArithmeticException would have problems because the child class had broken it. Stimulating unexpected errors violates overriden method principles.
However, the inverse scenario of narrowing down broader exemptions is completely permissible. A superclass method that normally throws an Exception could be safely changed to only throw an Illegal Argument Exception, which lowers the risk for callers.
25. Define chained exceptions in Java.
In a program, one exception can throw many exceptions by inducing a domino effect. This causes a chain of exceptions. It is beneficial to know the location of the actual cause of the exception. This is possible with the chained exceptions feature in Java. This has been introduced since JDK 1. 4. Two new constructors and two new methods have been added to the Throwable class so that chained exceptions can be handled in Java. These are,.
Constructors Of Throwable class:
- Throwable(Throwable cause): The cause is the exception that this one raises. Throwable(String msg, Throwable cause): The message is in the msg string. This is caused by the exception that throws the current exception.
Methods Of Throwable class:
- the getCause() method gives you the real reason why an exception was raised. throwable cause) method: This method sets the cause of the calling exception.
26. Which class is defined as a super class for all types of errors and exceptions in Java?
The super class for all types of errors and exceptions is java. lang. Throwable in Java. This superclass acts as a container for the main traits and behaviors that all the classes below it share. For example, it includes the ability to be tracked through stack traces and the tools for programmatic capture and propagation. Everything that can be “thrown” (using syntax like throw new Exception()) starts with Throwable at the top level.
It has two child classes, Error and Exception, which handle exceptions in Java. Errors are usually caused by hardware or system failures that can’t be fixed by code, while Exceptions are recoverable errors that happen in application logic or user input validation. This fork separates more uncontrollable low-level problems from flow defects that are tuneable within software design.
27. What can classify as a correct combination of try, catch and finally blocks?
A combination of try and catch block.
A combination of try and finally block.
A combination of all three: try, block, finally blocks.
28. Why do you use printStackTrace() method?
This method is used to print detailed information about the exceptions that occurred. Instead of just raising an exception and maybe showing a high-level exception type or message, printStackTrace() shows the whole stack trace that led to the exception being raised at runtime.
This ability to see the calling of methods one after the other on the call stack that caused the crash is very helpful for finding the last line of code that caused the exceptional state. Developers can look at all of the stack frames in the exception pipeline to find the class, method, line number, and exact executable statement that caused the error.
Without printStackTrace(), debugging information like this might have to be gathered by hand, with logging statements placed at different levels of the architecture to find where errors are coming from.
29. What are some examples of checked exceptions?
Some examples of checked exceptions include ClassNotFoundException, SQLException, and IOException. By including these exception types in method signatures, users must be ready for possible failures and make sure they can recover using catches. Omitting declaration handling risks abrupt terminations so annotation promotes resilience. That’s why checked exceptions instil defensive coding habits accounting for fallibilities in broader environmental integrations crossing runtime boundaries. They notify callers that vigilance is advised when leveraging volatile external services. Handling ensures graceful degredation when instability inevitably arises.
30. What are some examples of unchecked exceptions?
Some examples of unchecked exceptions include NullPointerException, ArrayIndexOutOfBoundsException and NumberFormatException. Overall unchecked exceptions tend to reflect oversights in code itself rather than environmental issues. Letting these exceptions pop up right away shows where extra null checking, data validation, or defensive input handling could help stop problems early in the development process. Damage control uses try/catch blocks only around call sites requiring continuity after raising exceptions.
Compile-Time and Runtime Errors – Intro to Java Programming
FAQ
What is a compiler question answer?
Can you give me an example of when you made a mistake at work?
Which type of error compiler check?
What are some common compiler interview questions?
Here are 20 commonly asked Compiler interview questions and answers to prepare you for your interview: 1. What is a compiler? A compiler is a computer program that translates computer code written in one programming language into another programming language. 2. Can you explain what the front-end and back-end of a compiler are?
How to perform well at a compiler design interview?
Here are some tips you can follow to perform well at your compiler design interview: Read the job description carefully. Reading the job description carefully can help you understand the duties for the role better. It can also help you identify keywords that you may use in your answers during the interview.
How do I get a job as a compiler designer?
You may typically require facing an interview to get a job as a compiler designer or a similar role. Preparing answers to some questions that interviewers may ask can help you answer them confidently and increase your chances of advancing to the next stage of the interview.
What is error handling in compiler construction?
Error handling in compiler construction is a crucial process that ensures the correctness of source code. It involves two main stages: detection and recovery. In the detection stage, errors are identified during various phases of compilation. Lexical phase errors include misspelled keywords or invalid characters.
