21 Days to Prepare CS Core Subjects For Placements - OS, DBMS, CN & Software Engineering

In any computer science curriculum, some core theory subjects remain common alongside coding and data structures, such as DBMS (Database Management System), OS (Operating Systems), CN (Computer Networks), COA (Computer Organization and Architecture), Software Engineering, and System Design.

These subjects play a crucial role for freshers, especially in cracking interviews. In the upcoming article, we will discuss the importance of these CS core subjects in the interview process to become an SDE.

So, let us check how to prepare CS core subjects for the Interview in 21 days.

Importance of CS Core Subjects in Interviews

Many students tend to skip these subjects, but their significance should not be underestimated. Along with mastering DSA (Data Structures and Algorithms), a strong grasp of these concepts is essential.

Here’s why they matter:

• They form the foundation of computer science concepts.
• They help you excel in technical interviews.
• They give you a competitive edge over candidates with similar coding skills.

Day Wise topics Distribution

A. DBMS (Database Management System) [1^st -5^th Day]

Database Management System (DBMS) is considered the second most important subject after Data Structures and Algorithms. It is a software application that helps manage, organize, and manipulate databases, providing an interface to perform various operations while ensuring efficient data storage and retrieval.

• Basics of DBMS
  • Introduction of DBMS (Database Management System) | Set 1
  • Introduction of 3-Tier Architecture in DBMS | Set 2
  • DBMS Architecture 1-level, 2-Level, 3-Level
  • Advantages of DBMS over the File system
  • Introduction of ER Model
• Relational Algebra 
  • Introduction of Relational Algebra and Basic Operators
  • Types of Keys in the Relational Model (Candidate, Super, Primary, Alternate, and Foreign)
  • Inner Join vs Outer Join
  • Join operation Vs nested query 
• Normalization
  • Introduction
  • Normal Forms
  • Lossless Join Decomposition
  • Introduction of 4th and 5th Normal form
  • Denormalization in Databases
• Transactions and Concurrency Control 
  • Introduction
  • ACID Properties
  • Concurrency Control -Introduction
  • Implementation of Locking in DBMS
  • Types of Schedules
  • Conflict Serializability
  • View Serializability
  • Starvation in DBMS
  • Deadlock in DBMS
• SQL Tutorial
  • Introduction to SQL
  • SQL DataTypes
  • SQL Operators
  • SQL Clauses
  • SQL Functions
  • Aggregate Functions and Scaler Functions
  • SQL Queries
  • Quiz on SQL

Useful links:

• DBMS Tutorial – Database Management System
• SQL | Tutorials

B. Operating Systems: [6^th -12^th Day]

The second subject in this series is Operating Systems (OS), one of the broadest and most crucial subjects. Understanding OS is essential for developers to know the internal working of the machine they work on. In many interviews and national qualifiers, a lack of OS knowledge can even lead to rejection or elimination. Hence, it’s vital to prepare thoroughly.

• Introduction of Operating System
  • Types of Operating Systems
    • Multiprogramming in Operating System
      • Time-Sharing Operating System
      • What is a Network Operating System?
      • Real-Time Operating System (RTOS)
    • Functions of the Operating System
• Process Management
  • Introduction of Process Management
  • Process Table and Process Control Block (PCB)
  • Operations on Processes
  • Context Switch in Operating System
  • Preemptive and Non-Preemptive Scheduling
• CPU Scheduling in OS
  • CPU Scheduling in Operating Systems
  • CPU Scheduling Criteria
  • Multiple-Processor Scheduling in Operating System
  • Thread Scheduling
• Process Synchronization
  • Introduction of Process Synchronization
  • Race Condition Vulnerability
  • Critical Section in Synchronization
  • Mutual Exclusion in Synchronization
• Critical Section Problem Solution
  • Semaphores in Process Synchronization
  • Semaphores and their types
  • Readers-Writers Problem
  • Producer Consumer Problem using Semaphores
• Deadlocks & Deadlock Handling Methods
  • Introduction of Deadlock in Operating System
  • Conditions for Deadlock in Operating System
  • Banker’s Algorithm in Operating System
  • Handling Deadlocks
• Memory management
  • Memory Management in Operating System
  • Paging in Operating System
  • Segmentation in Operating System
  • Virtual Memory in Operating System
• Page Replacement Algorithms
  • Page Replacement Algorithms in Operating Systems
  • Belady’s Anomaly in Page Replacement Algorithms
  • Optimal Page Replacement Algorithm

Useful links:

• Last Minute Notes – Operating Systems
• Commonly Asked Operating Systems Interview Questions

C. Computer Networks:[ 13^th - 16^th Day]

Computer Networks may not be asked frequently in SDE interviews, but there’s always a chance of facing a few basic networking questions. It’s an essential subject for roles like network administrator, system administrator, or network engineer, where managing or maintaining network infrastructure is key. Having a good grasp of networking can give you an edge over other candidates with similar knowledge, helping your candidature stand out.

• Basics of Computer Networks
  • Basics of Computer Networking
  • Network Topologies
  • Introduction to basic Networking terminology
  • Types of area networks – LAN, MAN, and WAN
  • TCP/IP Model
  • Layers of OSI Model
• Data Link Layer
  • Local Area Network (LAN) Technologies.
  • Introduction of MAC Address
  • Carrier sense multiple access (CSMA)
  • Basics of Wi-Fi
  • Virtual LAN (VLAN)
  • Stop and Wait for ARQ
  • Sliding Window Protocol 
• Network Layer
  • Introduction and IPv4 Datagram Header
  • IP Addressing 
  • Types of routing
  • Unicast Routing – Link State Routing
  • Wifi protected access (WPA)
  • Wifi-protected setup (WPS)
  • LiFi vs. WiFi
  • Differences between IPv4 and IPv6
• Transport Layer
  • TCP Connection Establishment
  • Transport Layer responsibilities
  • Multiplexing and Demultiplexing in Transport Layer
  • User Datagram Protocol (UDP)
  • P2P(Peer To Peer) File Sharing
  • Congestion Control
  • TCP Congestion Control
  • Congestion control techniques
• Application Layer
  • Protocols in the Application Layer
  • Simple Mail Transfer Protocol (SMTP)
  • DNS (Domain Name Server)
  • What’s the difference between http:// and https://?
  • File Transfer Protocol (FTP)
  • Asynchronous Transfer Mode (ATM)
  • Dynamic Host Configuration Protocol (DHCP)

Useful Links:

• Quiz on Data Link Layer
• Quiz on Network Layer
• Quiz on IP addressing
• Quiz on Transport Layer
• Quiz on Application Layer

D. Software Engineering: [17^th - 21^st Day]

The final subject in our series is Software Engineering, which involves the design, development, testing, and maintenance of software systems. It’s a multidisciplinary field combining technical skills, problem-solving, and collaboration. In interviews, candidates are expected to know the Software Development Life Cycle (SDLC), different lifecycle models, and basics of Software Project Management, as these are vital for handling real-world projects. A solid understanding of Software Engineering can greatly boost your chances in any interview process.

• Introduction
  • Introduction to Software Engineering
  • Classification of Software
• Software Development Life Cycle
  • Classical Waterfall Model
  • Iterative Waterfall Model
  • Spiral Model
  • Rapid application development model(RAD)
  • RAD Model vs Traditional SDLC
  • Agile Development Models
  • Comparison of different life cycle models
  • Coupling and Cohesion
• Software Project Management
  • Project Management Process
  • COCOMO Model
  • Integrating Risk Management in SDLC
  • Role and Responsibilities of a Software Project Manager
• Software Requirements
  • Classification of Software Requirements
  • How to Write a good SRS for Your Project
  • Quality Characteristics of a Good SRS
  • Requirements Elicitation
• Software Testing and Debugging
  • Seven Principles of software testing
  • Testing Guidelines
  • Black box testing
  • White box Testing
  • Debugging
  • Integration Testing,