LECTURE 5 IN COMPUTER SCIENCE ENGINEERING

Lecture 5: Operating Systems

A computer system is incomplete without an Operating System (OS). The OS is the manager of all hardware and software resources. It acts as a bridge between the user and the computer hardware, ensuring smooth execution of programs and efficient resource utilization.

1. Definition of Operating System

An Operating System is system software that manages hardware resources, provides services to applications, and creates an environment for users to interact with a computer.

Example OS: Windows, Linux, macOS, Android, iOS.

2. Functions of an Operating System

• Process Management – Handles creation, execution, and termination of programs.
• Memory Management – Allocates and deallocates memory space to processes.
• File System Management – Organizes data storage and retrieval on disks.
• Device Management – Controls input/output devices (printers, disks, keyboards).
• Security & Access Control – Protects data and prevents unauthorized access.
• User Interface – Provides CLI (Command Line Interface) or GUI (Graphical User Interface).

3. Types of Operating Systems

• Batch OS – Executes jobs in batches without user interaction (early computers).
• Time-Sharing OS – Multiple users share system resources simultaneously.
• Distributed OS – Manages multiple interconnected systems as one.
• Real-Time OS (RTOS) – Executes tasks within strict deadlines (used in robotics, aviation).
• Mobile OS – Optimized for smartphones and tablets (Android, iOS).

4. Process Management

A process is a program in execution. The OS manages processes by:

1. Creating processes.
2. Scheduling CPU time for each process.
3. Handling process synchronization and communication.
4. Terminating processes when complete.

Process Scheduling Algorithms:

• FCFS (First Come First Serve) – Processes handled in arrival order.
• SJF (Shortest Job First) – Prioritizes shortest execution time.
• Round Robin – Each process gets equal time in rotation.
• Priority Scheduling – Based on process priority.

5. Memory Management

The OS manages memory allocation so processes do not interfere with each other. Techniques include:

• Contiguous Allocation – Memory assigned in continuous blocks.
• Paging – Divides memory into fixed-size pages.
• Segmentation – Divides memory into variable-sized segments.
• Virtual Memory – Uses disk storage to extend physical RAM.

6. File System Management

The OS organizes data into a file system so users can store and retrieve information easily.

• File creation, deletion, reading, and writing.
• Directory management (folders).
• Access permissions and security.
• Examples of file systems: FAT32, NTFS, EXT4.

7. Example: Simple OS Commands

# Linux Commands
ls       # List files
cd dir   # Change directory
rm file  # Remove file

# Windows Commands
dir      # List files
cd dir   # Change directory
del file # Delete file
  

These simple commands illustrate how an OS enables users to interact with the file system.

8. Importance of Studying Operating Systems

• Helps understand how software interacts with hardware.
• Forms the basis of system programming and application development.
• Knowledge of OS internals is essential for careers in cybersecurity, cloud computing, and network administration.
• Efficient OS design improves system performance and stability.

“The Operating System is the silent manager of your computer—coordinating, securing, and optimizing every task you perform.”

9. Summary of Key Points

• An Operating System is system software that manages resources and provides services.
• Functions: process, memory, file, device, and security management.
• Types: Batch, Time-Sharing, Distributed, Real-Time, Mobile OS.
• Process scheduling ensures fairness and efficiency.
• Memory management uses techniques like paging, segmentation, and virtual memory.
• File systems organize and secure data storage.

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✦ Lecture 5 prepared under the authority of English Master Institute (EMI) Worldwide ✦

LECTURE 6 ON COMPUTER SCIENCE ENGINEERING