CS Notes
Free notes for placement interviews on operating systems, computer networks, DBMS and OOP — worked examples, comparison tables and interview questions.
Where can I read OS, CN, DBMS and OOP notes for placements?
CodeKairo's CS notes cover the four subjects asked after the coding round — Operating Systems, Computer Networks, DBMS and Object-Oriented Programming — one page per topic, in reading order. Each note gives the definition you can say in an interview, how the thing works, a worked example you can reproduce on paper (Gantt charts, subnetting, normalization, page replacement), comparison tables, common mistakes and the questions interviewers ask, with answers. OOP notes carry programs in C++, Java and Python that are run before they are published. All of it is free to read without an account.
Operating Systems
Processes, threads, CPU scheduling, synchronization, deadlocks, memory, virtual memory, file systems and disk scheduling. All OS notes.
- Introduction to Operating Systems 11 min
- Processes and Threads 12 min
- CPU Scheduling Algorithms 15 min
- Process Synchronization 14 min
- Classic Synchronization Problems 10 min
- Deadlocks in Operating Systems 15 min
- Memory Management 13 min
- Virtual Memory and Demand Paging 13 min
- Page Replacement Algorithms 14 min
- File Systems 13 min
- Disk Scheduling Algorithms 11 min
- Inter-Process Communication 11 min
Test yourself: Operating Systems · Basic · Operating Systems · Intermediate
Computer Networks
The OSI and TCP/IP models, IP addressing and subnetting, TCP and UDP, DNS, HTTP, routing and what happens when you type a URL. All CN notes.
- Introduction to Computer Networks 12 min
- The OSI Model 10 min
- The TCP/IP Model 9 min
- IP Addressing and Subnetting 13 min
- TCP and UDP 14 min
- Domain Name System (DNS) 10 min
- HTTP and HTTPS 13 min
- Routing and Routing Protocols 14 min
- Data Link Layer: Framing, Error Control and MAC 15 min
- NAT, DHCP and Ports 11 min
- What Happens When You Type a URL 12 min
- Network Security Basics 14 min
Test yourself: Computer Networks · Basic · Computer Networks · Intermediate
Database Management Systems
ER models, keys, normalization, SQL joins and aggregation, transactions and ACID, concurrency control and indexing. All DBMS notes.
- Introduction to DBMS 11 min
- ER Model in DBMS 13 min
- Keys in DBMS 11 min
- Functional Dependencies in DBMS 13 min
- Normalization in DBMS: 1NF to BCNF 15 min
- SQL Basics: DDL, DML, DCL and TCL 11 min
- SQL Joins 12 min
- SQL GROUP BY, HAVING and Subqueries 12 min
- Transactions and ACID Properties in DBMS 12 min
- Concurrency Control in DBMS 16 min
- Indexing and B+ Trees in DBMS 15 min
- SQL vs NoSQL Databases 13 min
Test yourself: SQL · Basic · SQL · Intermediate
Object-Oriented Programming
Classes and objects, encapsulation, inheritance, polymorphism, abstraction, SOLID and the design patterns interviews ask for. All OOP notes.
- Introduction to Object-Oriented Programming 12 min
- Classes and Objects 14 min
- Encapsulation 13 min
- Inheritance 15 min
- Polymorphism 15 min
- Abstraction: Abstract Classes and Interfaces 15 min
- Association, Aggregation and Composition 14 min
- SOLID Principles 16 min
- Design Patterns for Interviews 18 min
- Object Equality, Hashing and Copying 16 min
- Exception Handling in OOP 16 min
Test yourself: OOP · Basic · OOP · Intermediate
How it works
- Pick a subject. Operating Systems, Computer Networks, DBMS or OOP — each lists its notes from the basics to the deepest topics.
- Read in order. Every note answers its question in the first lines, then teaches it with examples and tables, and links to the next note.
- Test yourself. Each subject links to its proctored skill test; a pass earns a verifiable credential for your profile and LinkedIn.
Who it is for
Final-year students before placement drives and anyone preparing for a technical interview's fundamentals round.