Top 10 Computer Programmer Interview Questions and Answers [Updated 2024]

Sample Answer
Object-Oriented Programming (OOP) is a programming paradigm that is based on the concept of ‘objects’, which can contain data and code. Data in the form of fields, also known as attributes, and code in the form of procedures, also known as methods. In OOP, the computer programs are designed using the concept of objects that interact with real-world entities. The four basic principles of OOP are Encapsulation, Inheritance, Polymorphism, and Abstraction. Encapsulation is the mechanism that binds code and data together and keeps them safe from outside interference or misuse. Inheritance is a way of creating a new class using properties of an existing class. Polymorphism allows one interface to be used for a general class of actions. And abstraction is a mechanism to represent the essential features without including background details.

Sample Answer
‘==’ in JavaScript is called the loose equality operator. It compares two values for equality, after converting both to a common type. On the other hand, ‘===’ is the strict equality operator that checks if the two values are equal in type and in value, without doing any type coercion. For instance, if we compare 2==’2′ it will return true because ‘==’ converts the string ‘2’ to a number before comparison. However, 2===’2′ will return false because ‘===’ doesn’t do any type conversion, and number 2 and string ‘2’ are not the same type.

Sample Answer
Merge sort is a type of sorting algorithm that follows a divide and conquer approach. It involves dividing the unsorted list into N sublists, where each sublist contains one element, which is considered sorted. The process of merging takes place, where the smaller sublists are merged into a new list, maintaining the sorted order. The process continues until we get a sorted list of N elements. For example, if we have an array of [38, 27, 43, 3, 9, 82, 10], it would first be divided into subarrays until each array only contains one element, then they would be merged back together in a sorted order.

Sample Answer
A stack is a data structure that follows the Last-In-First-Out (LIFO) principle. That means the last element added to the stack will be the first one to be removed. Stacks are often used in recursion implementation, parsing, and memory management. On the other hand, a queue is a data structure that follows the First-In-First-Out (FIFO) principle. So, the first element added to the queue will be the first one to be removed. Queues are commonly used in scenarios where we want to maintain the order of elements, like in CPU scheduling, Disk Scheduling, etc.

Sample Answer
Recursion in programming refers to a function that calls itself in order to solve a problem. This method is based on the principle of solving a complex problem by breaking it down into smaller, more manageable problems. A recursive function typically has two parts: a base case, which defines the solution to a simple instance of the problem, and a recursive case that expresses the solution in terms of a call to the same function on a smaller instance of the problem. For example, the calculation of a factorial is a common use case for recursion. The base case would be that the factorial of 0 is 1, and the recursive case would define the factorial of any other number n as n times the factorial of (n-1). While recursion can make the code cleaner and easier to understand, it can also lead to performance issues if not used carefully, as each recursive call adds a layer to the system’s call stack.

Sample Answer
Polymorphism is one of the four fundamental principles of Object-Oriented Programming (OOP). It allows routines to use variables of different types at different times. An operator or function can behave differently in different contexts. For instance, let’s take an example of a ‘draw’ method in a ‘Shape’ class. This method can be overridden by each derived class like ‘Circle’, ‘Rectangle’, ‘Triangle’ etc. Each ‘draw’ method will have a different implementation according to the specific shape. So, when we call the ‘draw’ method, it will execute the appropriate method related to the specific object. This is polymorphism. Polymorphism is essential in OOP as it enhances the flexibility and reusability of the code, allowing the same name to be used for methods that perform a similar but not identical task.

Sample Answer
Inheritance in Object-Oriented Programming is a feature that allows a class (child class) to acquire the properties and methods of another class (parent class). This is an essential feature in OOP as it promotes code reusability and a form of organization where properties and methods are defined once and used multiple times. For example, if we have a class ‘Vehicle’ with properties like ‘color’ and ‘speed’, and methods like ‘accelerate’ and ‘brake’, we can create another class ‘Car’ that inherits from ‘Vehicle’. This means the ‘Car’ class will automatically have ‘color’ and ‘speed’ properties, as well as ‘accelerate’ and ‘brake’ methods, without us having to define them again.

Sample Answer
Garbage collection in Java is a process that automatically reclaims memory that is no longer needed. This is done by removing objects that are not being used by the application anymore. There are different types of garbage collectors in Java, such as the Serial Collector, which is designed for single-threaded environments, the Parallel Collector, which is designed for multi-threaded environments, and the G1 Collector, which is designed for systems with large amounts of memory. If not managed correctly, garbage collection can have a negative impact on performance. For example, if the garbage collector runs too frequently, it can slow down the application as it uses CPU cycles. On the other hand, if the garbage collector does not run frequently enough, it can lead to memory problems as unused objects are not removed in a timely manner.

Sample Answer
Exception handling in Python is done using the try/except statement. When the code within a try block encounters an error during its execution, the flow of control is passed to a corresponding except block, which contains code to handle the error. There are also optional else and finally clauses. The else block is executed if the try block does not raise any exceptions, and it is typically used for code that must be executed if the try block is successful. The finally block is always executed, regardless of whether an exception was raised or not, and it is typically used for cleanup code. Exceptions can also be manually raised using the raise keyword, followed by the name of the exception to raise.

Sample Answer
Multithreading is an execution model that allows multiple threads to exist within the context of a single process, sharing the process resources but able to execute independently. The primary benefit of multithreading is that it increases the efficiency and performance of CPU by utilizing the idle time. It allows for simultaneous execution of two or more parts of a program for maximum utilization of CPU. Also, it’s commonly used for background tasks, UI updates, and tasks that could block the main thread. However, multithreading comes with its own challenges, such as dealing with synchronization and shared resource issues.