Fundamentals interview questions

What are variables and data types? Explain common primitive types.

Easy · Fresher, Fundamentals, Programming Fundamentals

Explain conditional statements (if/else, switch) and loops (for, while, do-while).

Easy · Fresher, Fundamentals, Programming Fundamentals

What is a function? Explain parameters, return types, and function calls.

Easy · Fresher, Fundamentals, Programming Fundamentals

What is an array? How do you traverse, search, and perform basic operations?

Easy · Fresher, Fundamentals, Programming Fundamentals

What are common string operations in interviews (length, reverse, compare, concatenate)?

Easy · Fresher, Fundamentals, Programming Fundamentals

What is the difference between compile-time and runtime errors?

Easy · Fresher, Fundamentals, Programming Fundamentals

What is variable scope? Explain local, global, and block scope.

Medium · Fresher, Fundamentals, Programming Fundamentals

What is pass by value vs pass by reference? How does it differ across languages?

Medium · Fresher, Fundamentals, Programming Fundamentals

What is recursion? Explain base case, recursive case, and common examples.

Medium · Fresher, Fundamentals, Programming Fundamentals

What is Big O notation? Explain O(1), O(n), O(log n), and O(n²) with examples.

Medium · Fresher, Fundamentals, Programming Fundamentals

What are multi-dimensional arrays? How are they stored and accessed?

Medium · Fresher, Fundamentals, Programming Fundamentals

What are pointers/references? Why do they matter in languages like C/C++ and Java?

Medium · Fresher, Fundamentals, Programming Fundamentals

How do you dry-run a program and debug logic errors in an interview?

Medium · Fresher, Fundamentals, Programming Fundamentals

What is the difference between stack and heap memory?

Hard · Fresher, Fundamentals, Programming Fundamentals

Explain basic bit manipulation: AND, OR, XOR, left/right shift with use cases.

Hard · Fresher, Fundamentals, Programming Fundamentals

What is an Operating System and what are its main functions?

Easy · Fresher, Fundamentals, Operating Systems

What is the difference between a process and a thread?

Easy · Fresher, Fundamentals, Operating Systems

Explain the different states of a process in its lifecycle.

Easy · Fresher, Fundamentals, Operating Systems

What is the difference between user mode and kernel mode?

Easy · Fresher, Fundamentals, Operating Systems

What is a system call? Give a few common examples.

Easy · Fresher, Fundamentals, Operating Systems

What are common CPU scheduling algorithms? Explain FCFS, SJF, and Round Robin.

Medium · Fresher, Fundamentals, Operating Systems

What is a context switch and why is it considered expensive?

Medium · Fresher, Fundamentals, Operating Systems

What is a deadlock? What are the four necessary conditions for it to occur?

Medium · Fresher, Fundamentals, Operating Systems

What is the difference between a mutex and a semaphore?

Medium · Fresher, Fundamentals, Operating Systems

What is virtual memory? How does paging work?

Medium · Fresher, Fundamentals, Operating Systems

What is the difference between paging and segmentation?

Medium · Fresher, Fundamentals, Operating Systems

What is a page fault? What is thrashing and how do you avoid it?

Hard · Fresher, Fundamentals, Operating Systems

What is Inter-Process Communication (IPC)? List common mechanisms.

Medium · Fresher, Fundamentals, Operating Systems

What do fork(), exec(), and wait() do in Unix-like systems?

Medium · Fresher, Fundamentals, Operating Systems

What is a race condition and a critical section? How do you prevent them?

Medium · Fresher, Fundamentals, Operating Systems

What is the difference between preemptive and non-preemptive CPU scheduling?

Medium · Fresher, Fundamentals, Operating Systems

Explain the Producer–Consumer problem and how semaphores solve it.

Hard · Fresher, Fundamentals, Operating Systems

Compare deadlock prevention, avoidance, detection, and recovery.

Hard · Fresher, Fundamentals, Operating Systems

What is the Banker's algorithm and what problem does it solve?

Hard · Fresher, Fundamentals, Operating Systems

Explain the 7 layers of the OSI model with the role of each layer.

Easy · Fresher, Fundamentals, Computer Networks

What is the difference between the OSI model and the TCP/IP model?

Easy · Fresher, Fundamentals, Computer Networks

What is the difference between TCP and UDP? When would you use each?

Easy · Fresher, Fundamentals, Computer Networks

What is the difference between an IP address and a MAC address?

Easy · Fresher, Fundamentals, Computer Networks

What are the main differences between IPv4 and IPv6?

Easy · Fresher, Fundamentals, Computer Networks

What is the difference between a public IP and a private IP? What is NAT?

Easy · Fresher, Fundamentals, Computer Networks

What is the difference between a router, switch, and hub?

Easy · Fresher, Fundamentals, Computer Networks

What is the difference between latency, bandwidth, and throughput?

Easy · Fresher, Fundamentals, Computer Networks

What is a firewall and how does it protect a network?

Easy · Fresher, Fundamentals, Computer Networks

What is a port number? List some well-known ports and their services.

Easy · Fresher, Fundamentals, Computer Networks

What is client–server architecture? How does it differ from peer-to-peer?

Easy · Fresher, Fundamentals, Computer Networks

What is an API? Explain REST APIs at a high level.

Easy · Fresher, Fundamentals, Computer Networks

What is the difference between GET and POST HTTP methods?

Easy · Fresher, Fundamentals, Computer Networks

Explain the TCP 3-way handshake.

Medium · Fresher, Fundamentals, Computer Networks

What is a subnet mask and what does CIDR notation mean?

Medium · Fresher, Fundamentals, Computer Networks

What happens when you type a URL in the browser and press Enter?

Medium · Fresher, Fundamentals, Computer Networks

Explain the TCP 4-way connection termination.

Medium · Fresher, Fundamentals, Computer Networks

What is the difference between HTTP and HTTPS?

Easy · Fresher, Fundamentals, Computer Networks

List the common HTTP methods and explain when each is used.

Easy · Fresher, Fundamentals, Computer Networks

What are HTTP status code classes (1xx–5xx)? Give a common example of each.

Easy · Fresher, Fundamentals, Computer Networks

What is DNS and how does DNS resolution work?

Medium · Fresher, Fundamentals, Computer Networks

What is DHCP and how does it assign IP addresses (DORA)?

Medium · Fresher, Fundamentals, Computer Networks

What is ARP (Address Resolution Protocol) and why is it needed?

Medium · Fresher, Fundamentals, Computer Networks

What is ICMP? How do ping and traceroute use it?

Easy · Fresher, Fundamentals, Computer Networks

What is the difference between SSH and Telnet? Why prefer SSH?

Easy · Fresher, Fundamentals, Computer Networks

What is the difference between FTP, SFTP, and FTPS?

Easy · Fresher, Fundamentals, Computer Networks

What are the core principles of a REST API?

Medium · Fresher, Fundamentals, Computer Networks

What is the difference between cookies and sessions?

Medium · Fresher, Fundamentals, Computer Networks

What is CORS and why does it exist?

Medium · Fresher, Fundamentals, Computer Networks

How does the SSL/TLS handshake work at a high level?

Hard · Fresher, Fundamentals, Computer Networks

What are the key differences between HTTP/1.1 and HTTP/2?

Hard · Fresher, Fundamentals, Computer Networks

What is a WebSocket and how is it different from HTTP?

Hard · Fresher, Fundamentals, Computer Networks

What is load balancing? Explain common strategies.

Hard · Fresher, Fundamentals, Computer Networks

What is a CDN and how does it improve performance?

Hard · Fresher, Fundamentals, Computer Networks

What is a reverse proxy? How does it differ from a forward proxy?

Hard · Fresher, Fundamentals, Computer Networks

Explain HTML document structure and essential tags used in web pages.

Easy · Fresher, Fundamentals, Web & Full-Stack

What is the CSS box model? Explain margin, border, padding, and content.

Easy · Fresher, Fundamentals, Web & Full-Stack

What are JavaScript fundamentals every fresher should know?

Easy · Fresher, Fundamentals, Web & Full-Stack

What is the DOM? How do events like click and submit work?

Easy · Fresher, Fundamentals, Web & Full-Stack

What is the difference between frontend and backend development?

Easy · Fresher, Fundamentals, Web & Full-Stack

What are essential Git commands and the basic workflow?

Easy · Fresher, Fundamentals, Web & Full-Stack

How do CSS Flexbox and media queries enable responsive layouts?

Medium · Fresher, Fundamentals, Web & Full-Stack

Explain map, filter, and reduce with simple JavaScript examples.

Medium · Fresher, Fundamentals, Web & Full-Stack

What is the JavaScript event loop? Explain call stack and callback queue.

Medium · Fresher, Fundamentals, Web & Full-Stack

What are Promises, async, and await? How do they handle asynchronous code?

Medium · Fresher, Fundamentals, Web & Full-Stack

How do you make HTTP requests from the browser using the Fetch API?

Medium · Fresher, Fundamentals, Web & Full-Stack

What are React components, props, and state? Explain with a simple example.

Medium · Fresher, Fundamentals, Web & Full-Stack

How do Git branches, merge, and pull requests work in team projects?

Medium · Fresher, Fundamentals, Web & Full-Stack

What is the difference between localStorage and sessionStorage?

Medium · Fresher, Fundamentals, Web & Full-Stack

What is the same-origin policy in browsers?

Medium · Fresher, Fundamentals, Web & Full-Stack

How does JWT authentication work? Explain access tokens at a high level.

Hard · Fresher, Fundamentals, Web & Full-Stack

Compare session-based vs token-based authentication. When would you use each?

Hard · Fresher, Fundamentals, Web & Full-Stack

What is the difference between Server-Side Rendering (SSR) and Client-Side Rendering (CSR)?

Hard · Fresher, Fundamentals, Web & Full-Stack

How does CORS affect a full-stack app (e.g., React on :3000, API on :8080)?

Hard · Fresher, Fundamentals, Web & Full-Stack

What are common web performance optimizations for fresher-level apps?

Hard · Fresher, Fundamentals, Web & Full-Stack

Walk through a complete login flow: form → API → DB → token/session → protected route.

Hard · Fresher, Fundamentals, Web & Full-Stack