Top 50 Programming Interview Questions You Must Know To Land A Job

Top 50 Programming Interview Questions You Must Know To Land A Job

Want to get a job at Google or Amazon? Here are some of the best programming interview questions. You'll find them in this article. Read more here.

Programming and software development talent are always in high demand at big companies like Amazon, Google, and Microsoft. Therefore, one must accumulate as much knowledge as possible to become a part of big names like those mentioned above. To acquire this knowledge, you can learn programming from the best programming tutorials for beginners in 2021.

To make the job interview process easier for you, I have compiled a list of the top programming interview questions you must know. Additionally, if you approach an interview with promptness and subtlety, you are more likely to be chosen for the job. So read on for cracking the programming interview questions.

Frequently Asked Programming Interview Questions & Answers

Let's begin with some questions for beginners and then move on to the more experienced ones.

1. Explain Computer Programming.

Answer: The process of designing and implementing a computer program to perform a specific task or achieve a particular result is known as computer programming, also called coding.

Each programming language contains instructions for the computer to execute a specific task. It is a complex process that includes designing an algorithm, coding the same in a programming language, debugging a program, maintaining, and updating the code.

2. Please explain an algorithm. Name some of its important features?

Answer: An algorithm is a set of definite steps that can help in accomplishing a particular task when followed. Some notable features of the algorithm are - clarity, efficiency, and finiteness.

3. Give a brief explanation of the variables.

Answer: Variables are used to store input and computational results during the execution of a program. These are referred to as memory locations. During program execution, a value stored in a variable can change.

4. Could you explain arrays?

Answer: An array is a programming structure that consists of multiple data values of the same type. Memory-wise, an array is a collection of contiguous memory locations that store data of the same type.

5. What do you understand by machine code?

Answer: Machine language refers to a low-level programming language. Contrary to high-level programming languages that use compilers to transform high-level code into machine code for execution, a microprocessor directly processes machine code without doing such a transformation.

6. What do you mean by “beta version” of a computer program?

Answer: Usually, a beta version of a computer program or piece of software is a version that is not yet ready for public release and will need to be modified based on feedback from beta testers.

7. Please explain program execution.

Answer: In computer programming, program execution refers to carrying out instructions innate to the program by the computer. Moreover, the computer program must be loaded into the memory (RAM) of the computer before execution.

8. Why adding comments to code is highly advisable?

Answer: Almost every computer program includes hundreds of thousands of LOC (lines of code). Commenting simplifies the process of examining or finding things within the code more efficiently for others.

9. What is a compiler?

Answer: Compilers translate written code from one programming language into another. They are typically computer programs that convert source code about high-level programming languages to lower-level programming languages to generate an executable program.

Answer: There are several issues discovered while testing a computer program. It is called an error or a bug. Debugging is the process of fixing them. Essentially, debugging involves fixing failures discovered within an implementation code.

11. Can you enumerate some coding best practices?

Answer: These best coding practices will make your programming more efficient:

  • Keep the code as concise as possible.
  • Use comments often
  • Use consistent indentation
  • Limit the length of a line of code.
  • Abide by the DRY principle
  • Keep the code as concise as possible.
  • Use easy-to-remember naming conventions.
  • Avoid Deep Nesting whenever and wherever possible.

12. Explain the DRY principle?

Answer: DRY is short for Don't Repeat Yourself. It is a principle of software development that reduces the repetition of software patterns. In order to achieve this, either repetitive software patterns must be replaced with abstractions or data must be normalized.

13. What are the violations of the DRY principle called? Can you tell me where they are found typically?

Answer: We call these violations WET solutions. Generally, WET stands for Write Everything Twice, but sometimes it can also mean We Enjoy Typing or Waste Everyone's Time. Multi-tiered architectures are common with WET solutions.

14. What are some of the areas that leverage data structures?

Answer: Everywhere data is involved, data structures are required. Nevertheless, some notable examples include:

  • Artificial intelligence
  • Database Management
  • Compiler Design
  • Operating System
  • Statistical Analysis
  • Graphics
  • Numerical Analysis

Answer: The process of arranging the elements of an array in either ascending or descending order is called Sorting. Among the most popular sorting techniques are:

  • Merge sort
  • Bubble sort
  • QuickSort
  • HeapSort
  • Selection sort
  • Insertion sort

16. How will you reference all elements in a one-dimensional array?

Answer: Referencing all elements in a one-dimension array requires an indexed loop. The counter runs from 0 to a number equal to 1 fewer than the array size. Thus, all elements are referenced in sequence by using the loop counter as the array subscript.

17. Please explain a graph.

Answer: A graph is a type of data structure that consists of ordered pairs. Additionally, these ordered pairs are called arcs or edges. Moreover, they are used to connect nodes, which store and retrieve data.

18. Can you explain the multi-dimensional array?

Answer: Conventional arrays have only one index, while multi-dimensional arrays have multiple indexes. When single-dimensional indexing is not sufficient, it is used.

19. Please explain an AVL tree.

Answer: AVL trees are binary search trees that are always partially balanced. It is the first data structure of its kind. In this case, it is the height difference between the sub-trees from the root.

20. What is a recursive function?

Answer: Recursive functions refer to functions that call themselves. It uses a stack and a terminating condition. This process is known as recursion.

21. How does the recursive algorithm works?

Answer: In a recursive algorithm, problems are reduced into smaller, manageable chunks. Therefore, once a recursion is completed, the output gained after treating one sub-problem kicks off the next recursion process.

Answer: Fibonacci search is a type of search algorithm applied to sorted arrays. This method uses the divide-and-conquer technique to drastically cut down the time it takes to reach the target.

23. Why do we use Huffman’s algorithm?

Answer: Using Huffman's algorithm, we can extend binary trees with minimum weighted path lengths. Moreover, it uses a table that contains the total number of times for each data element.

24. What is the difference between NULL and VOID?

Answer: In general, NULL denotes a value, and VOID represents a data type identifier. When a variable has a NULL value, it represents an empty value. Moreover, VOID identifies pointers with no initial size.

25. Please explain how does dynamic memory allocation help in managing data?

Answer: The dynamic allocation of memory allows for storing simple structured data types. Moreover, it helps combine separate structure blocks to form composite structures that can be expanded and contracted as needed.

26. Please explain data abstraction.

Answer: Data abstraction simplifies complex data problems into more manageable sub-problems. As a result of data abstraction, the first data objects and operations to be carried out on them are specified. It becomes a secondary task to determine how the data objects will be stored in memory.

27. Please explain how variable declaration affects memory allocation.

Answer: A variable declaration defines a particular data type. Depending on the data type a variable belongs to, the amount of memory it needs to store will differ.

28. Can you enumerate and explain the various types of errors that can occur during the execution of a computer program?

Answer: Errors may occur in three different ways during the execution of a computer program:

  • Logical Errors: In this case, a computer program implements the wrong logic. There is no report generated for these specific programming errors, so they are the most difficult to deal with.

  • Runtime Errors: Programs that contain illegal operations cause this error. For example, dividing a number by 0. During program execution, these are the only errors that are displayed instantly. If a runtime error occurs, the program is stopped, and a diagnostic message is displayed.

  • Syntax Errors: A programming error occurs when one or more grammar rules of the language are violated. Errors of this type are detected during compilation.

29. What do you understand by maintaining and updating a computer program?

Answer: After a computer program has been successfully installed, it begins to undergo maintenance and updates. Program maintenance involves monitoring the computer program for bugs and errors over time. However, updating the computer program means making it better with minor and substantial changes over time.

30. Every programming language has reserved words. What are they? Give some examples.

Answer: Reserved words, or keywords, typically have predetermined meanings in a particular programming language. Reserved words cannot be used or redefined for any other purpose. Here are some examples of reserved words:

  • Java: abstract, boolean, catch, class, const, double, enum, finally, implements, instanceof, throws, transient, and volatile.
  • C: break, case, char, default, else, float, if, and int.
  • Python: and, assert, continue, def, del, global, not, lambda, raise, and yield.

31. What are constants? Explain their types.

Answer: Constants are programming entities whose values cannot be changed or modified during program execution. There are two main types of constants:

  1. Numeric Constants: It consists of integers, single-precision, and double-precision numbers. For instance, 22, 24, -898, 4.5, and 73.45.
  2. String Constants: It contains a series of alphanumeric characters enclosed in double quotation marks. String constants can have a maximum length of 255 characters. "Shimla," "I Love You," and "Orange Is the New Black" are a few examples.

32. Please explain program documentation. Why is it important?

Answer: It is the written description of the algorithm(s), coding method, design, testing, and appropriate usage of a particular computer program. The program documentation is useful for those who use the computer program regularly and for the programmer(s) who would need to correct, modify, and update the program.

A serious programmer must have reliable documentation. It is important to keep detailed documentation of computer applications in order not only to manage the various aspects of the application but also to improve its quality. Development, maintenance, and knowledge transfer are the main objectives of program documentation.

33. What do you understand by loops? Briefly explain the various types of loops.

Answer: Loops are structures in programming that repeat a defined set of statements for a set number of times or until a certain condition is met. Three types of loops are important:

  • For NEXT Loop: This loop is the most effective if you know in advance how many times it will be repeated
  • While WEND Loop" It repeats a particular action until the condition is no longer true. This loop is helpful when the total number of repetitions is unknown.
  • Nested Loop: Using a loop inside another loop is known as a nested loop.

34. Please explain the operators.

Answer: Computer programs use operators to perform certain operations on data. Symbols represent them. For example, / represent mathematical division while * represents multiplication. There are four main types of operators:

  • Arithmetic: It is used for performing mathematical operations
  • Assignment: It is used for storing values, strings, computational results, and data in variables.
  • Logical: In other words, logical operators allow combining simple conditions to form more complex conditions.
  • Relational: – Used for defining or testing some kind of relation between two entities. These operators evaluate to either true or false and produce a non-zero value.

35. What do you understand by a subroutine?

Answer: A subroutine is a set of statements that can be called from anywhere within a computer program. After the subroutine has completed its intended task, it returns control to the section of the program called the subroutine.

36. Do you know about modeling languages? Give some examples.

Answer: An artificial language that expresses information, knowledge, or systems according to a set of rules is described as a modeling language. Also, a set of rules is used to interpret the meaning of the components of a modeling language structure. Modeling languages include the following:

  • Business Process Modeling Notation
  • Extended Enterprise Modeling Language
  • Flowchart
  • Jackson Structured Programming
  • Systems Modeling Language
  • Unified Modeling Language

37. Please explain software testing. Why do we need it?

Answer: Software testing is an important part of every software development life cycle model, whether it is the traditional waterfall model or the modern Rapid Application Development (RAD) model. The software is tested under certain conditions to check its quality as part of the software testing process. It is also important to test a computer program to determine whether it delivers a good user experience. Other reasons include:

  • Meeting user requirements
  • Checking for improvements
  • Ensure proper/intended working

38. What do you understand by program implementation?

Answer: Once a computer program has successfully passed software testing, it must be installed and made operational on the targeted computer(s). This process of preparing an application for end-user use and installing the program is called program implementation.

39. Please explain bubble sorting?

Answer: Bubble sorting is a sorting algorithm that involves continuously comparing adjacent elements in a data structure, such as an array until we get the right sort order. If the compared elements are in the wrong order, they are swapped.

Bubble sort enables the lowest values to bubble to the top, hence the name. It is also called a sinking sort, as the larger values sink to the bottom.

40. Please explain data structures.

Answer: Data structures are ways of organizing and manipulating data. It facilitates the smooth exchange of data as well as its modification.

Data structures can also be defined as sets of data, functions that apply to them, and relationships between them. Data structures include arrays, linked lists, heaps, graphs, and stacks.

41. Name some modeling languages.

Answer: Below are some names of modeling languages:

  • Business Process Modeling Notation
  • Jackson Structured Programming
  • FlowChart
  • Fundamental Modeling Concepts
  • Unified Modeling Language
  • Alloy (specification language
  • Systems Modeling Language
  • Extended Enterprise Modeling Language

42. What is the difference between a linear and a non-linear data structure?

Answer: Linear data structures place data elements next to each other. This data structure includes arrays, linked lists, queues, and stacks.

The data elements of a nonlinear data structure can be interconnected with more than two other data elements. Graphs and trees are examples of non-linear data structures.

Answer: Binary search is best applied to lists in which all elements have already been sorted. The binary search begins by searching in the middle of the list.

When the middle element is not the targeted element, it searches either the lower half of the upper half of the list. Until the desired element is found, the process is repeated.

44. What do you understand by LIFO and FIFO?

Answer: LIFO and FIFO are two of the most popular methods for accessing, retrieving, and storing data. Last In First Out is the acronym for LIFO. Therefore, the most recent data stored is retrieved first in this approach. After that, the stack follows this approach.

In contrast to LIFO, FIFO stands for First In First Out. In this case, the oldest data is the first to be retrieved. In a queue, the FIFO approach is followed.

45. How to convert numeric String to int in Java?


public class StringToInteger { public static void main(String args[])
String integer = "237"; 
int number = new Integer(integer); 
System.out.println("Integer created from String in Java : " + number);  number = Integer.parseInt(integer); 
System.out.println("String to int using parseInt() : " + number);  number = Integer.valueOf(integer); 
System.out.println("String to int Conversion example using valueOf : " + number); 
String negative = "-237"; 
System.out.println("Converting negative String to int in Java");
System.out.println("String to Integer Constructor Example :" + new Integer(negative)); 
System.out.println("String to Integer parseInt Example : " + Integer.parseInt(negative)); 
System.out.println("String Integer valueOf Example : " + Integer.valueOf(negative));


Integer created from String in Java: 237 
String to int using parseInt() : 237
String to int Conversion example using valueOf : 237 
Converting negative String to int in Java 
String to Integer Constructor Example : -237 
String to Integer parseInt Example : -237
String Integer valueOf Example : -237

46. Write a method that will remove any given character from a String?


public class RemoveChar {  
    public static void main(String[] args) {  
              String str = "How are you"; 
              System.out.println(charRemoveAt(str, 7));  
           public static String charRemoveAt(String str, int p) {  
              return str.substring(0, p) + str.substring(p + 1);  


How are you

47. What is the code to check if a String is palindrome or not?


#include <string.h>
int main()
    char a[1000];  
    int i,n,b=0;
    printf("Enter  the string : ");
       printf("string is palindrome");
        printf("string is not palindrome");
    return 0;


Enter the string: madam
String is palindrome

48. How to check if two String are Anagram?


import java.util.Arrays;
import java.util.Collections;
class Anagram {
    static boolean areAnagram(char[] str1, char[] str2)
        // Get lenghts of both strings
        int n1 = str1.length;
        int n2 = str2.length;
        // If length of both strings is not same,
        // then they cannot be anagram
        if (n1 != n2)
        return false;
        // Sort both strings
        // Compare sorted strings
        for (int i = 0; i < n1; i++)
            if (str1[i] != str2[i])
                return false;  
                return true;
    public static void main(String args[])
        char str1[] = { 'w', 'e', 's', 't' };
        char str2[] = { 't', 't', 'e', 'w' };
        if (areAnagram(str1, str2))
            System.out.println("The two strings are"
                               + " anagram of each other");
            System.out.println("The two strings are not"
                               + " anagram of each other");


The two strings are not an anagram of each other.

49. Write a program to implement a blocking queue in Java?


import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
public class ProducerConsumer {
public static void main(String[] args) {      
     BlockingQueue<Message> queue = new ArrayBlockingQueue<>(10);
     Producer producer = new Producer(queue);    
     Consumer consumer = new Consumer(queue);
     new Thread(producer).start();
     new Thread(consumer).start();
     System.out.println("Producer and Consumer started");


Producer and Consumer started
Produced 0
Produced 1
Produced 2
Produced 3
Produced 4
Consumed 0
Produced 5
Consumed 1
Produced 6
Produced 7
Consumed 2
Produced 8

50. Why String is final in Java?

Answer: In Java, the string is final to ensure performance security for two main reasons. First, when strings are mutable, they can be easily attacked, as strings are used as database URLs and network connections. Second, if Strings are immutable, so there are no synchronization issues, as the string becomes thread-safe.

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