JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II OPERATING SYSTEMS Previous Question Paper (March - 2022 - R16)

Operating System services provide an environment for the execution of programs and the services to the programs and users. Key services include:

• Program Execution: The system must be able to load a program into memory and run it, including handling program termination.
• I/O Operations: Since user programs cannot execute I/O operations directly, the OS provides a means to perform these operations on behalf of the user.
• File-System Manipulation: The OS manages the creation, deletion, reading, writing, and directory management of files.
• Communications: Processes may need to exchange information, either on the same computer or via a network, using shared memory or message passing.
• Error Detection: The OS constantly monitors for errors in the CPU, memory, I/O devices, or user programs to ensure consistent computing.
• Resource Allocation: The OS manages resources like CPU cycles, main memory, and file storage for multiple users or jobs.
• Accounting: The system tracks which users use how many and what kinds of resources for billing or usage statistics.

Protection and security are essential for multi-user and networked systems to ensure integrity and confidentiality.

Protection refers to a mechanism for controlling the access of programs, processes, or users to the resources defined by the computer system. It provides a means for the system to distinguish between authorized and unauthorized usage, ensuring that processes operate within their assigned memory spaces and access only the files they are permitted to use. This is enforced through mechanisms like access control lists and user authentication.

Security refers to measures taken to defend the system against internal and external attacks. These include threats such as viruses, worms, denial-of-service attacks, and unauthorized data breaches. Security involves authentication (verifying the identity of a user via passwords or biometrics), encryption (protecting data during transmission or storage), and firewalls to monitor and control network traffic. While protection is internal to the system's resource management, security is a broader defense against malicious intent.