An operating system (OS) is a software that manages hardware resources and provides services for computer programs. It is the most fundamental system software that is responsible for managing the overall functionality of a computer system. An OS plays a crucial role in facilitating communication between the user, computer hardware, and applications. It provides an environment where users can interact with the computer and run applications.

User Services:

An operating system provides several services to users to help them interact with the computer. These services include:

Operating System Services Diagram by Learn Loner

User Interface:

The OS provides a user interface (UI) that allows users to interact with the computer through a graphical user interface (GUI) or a command-line interface (CLI). The UI provides various tools and applications that users can use to manage their files, applications, and settings.

File Management:

The OS provides a file management system that allows users to create, delete, copy, move, and organize files and directories on the computer’s storage devices.


The OS provides security features to protect user data and system resources from unauthorized access. It includes user authentication, access control, and data encryption.


The OS provides printing services that allow users to print documents on printers connected to the computer.

Multimedia Support:

The OS provides multimedia support for audio and video playback, as well as support for image viewing and editing.

Process Management:

An operating system manages processes, which are instances of programs that are currently running on the computer. The OS provides several services to manage processes efficiently. These services include:

Process Scheduling:

The OS schedules processes to run on the CPU in a way that optimizes system resources and ensures fairness.

Process Synchronization:

The OS provides mechanisms to allow processes to synchronize their activities and avoid conflicts.

Memory Management:

The OS manages memory allocation and deallocation for processes and ensures that each process has access to the memory it needs.

Input/Output Management:

The OS manages input/output (I/O) operations for processes and ensures that I/O requests are handled efficiently.

Error Handling:

The OS provides error handling services to detect and recover from errors that may occur during process execution.

System Services:

An operating system provides several services to other system components and applications. These services include:

Device Drivers:

The OS provides device drivers that allow applications to communicate with hardware devices such as printers, scanners, and network adapters.


The OS provides networking services that allow applications to communicate over the network and access remote resources.


The OS provides virtualization services that allow multiple operating systems to run on the same physical hardware.


The OS provides security services to protect the system from viruses, malware, and other security threats.

Resource allocation: The OS manages system resources such as CPU, memory, and I/O devices and allocates them to processes and applications as needed.



(a) Write are the functions of operating systems? write a note on multi programmed operating systems ?

(b) Distinguish between client server and peer to peer model of distributed systems .


(a) With a Neat Sketch, Describe the services that an Operating System provides to users, processes and other systems.

(b) What is meant by Storage Structure? Discuss Storage Hierarchy.

(c) Write the Advantages and Disadvantages of using the same system call interface for manipulating both Files and Devices.


(a) What are the criteria for evaluating the CPU scheduling algorithms? Why do we need it?

(b) Define process. Explain various steps involved in change of a process state with process state neat transition diagram.


(a) What is synchronization? Explain how semaphores can be used to deal with n-process critical problem.

(b) Define a thread. Give the benefits of multithreading. What resources are used when a thread is created?


(a) How dose deadlock avoidance differ from deadlock prevention? Write about deadlock avoidance algorithm in detail.

(b) Different between external fragmentation and internal fragmentation. How to solve the fragmentation using paging?


(a) What is the purpose of paging the page table? Consider the following page reference string 1,2,3,4,5,1,2,3,4,5 for a memory with three frames. How many page faults would LRU and FIFO replacement algorithm?

(b) What are the disadvantages of single contiguous memory allocation? Explain.


(a) Briefly explain about single-level, two-level and three Structured directories.

(b) What is disk scheduling? Explain the C-SCAN scheduling by giving an example.


(a) Interrupt and spooling.

(b) UNIX file system.

(c) Program and system threats.

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