JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD MCA 2021 OPERATING SYSTEMS Previous Question Paper (July/August - 2021 - R20)

A Time-Shared Operating System allows multiple users to share the computer system simultaneously by switching the CPU rapidly between tasks. Each user is allocated a small time slice or quantum. Because the CPU switches between processes so quickly, each user perceives that they have the entire system to themselves, which improves interactivity and resource utilization.

A Real-Time Operating System (RTOS) is designed for environments where processors must respond to input within a strict, predefined time constraint. These systems are categorized into:

• Hard Real-Time Systems: Guarantee that critical tasks are completed on time; failure to meet a deadline results in total system failure (e.g., medical life support or flight control systems).
• Soft Real-Time Systems: Prioritize critical tasks over less important ones, but missing a deadline is undesirable rather than catastrophic (e.g., multimedia streaming or virtual reality).

An Operating System (OS) is a system software that acts as an intermediary between the computer hardware and the user, managing system resources and providing common services for computer programs.

The primary services provided by an OS include:

• Process Management: Creating, deleting, suspending, and resuming processes, and providing mechanisms for process synchronization and communication.
• Memory Management: Keeping track of which parts of memory are currently in use and by whom, and allocating/deallocating memory space as needed.
• File Management: Managing files and directories, including creation, deletion, reading, writing, and controlling access permissions.
• I/O System Management: Managing device drivers to hide the peculiarities of specific hardware devices from the user.
• Secondary Storage Management: Managing free space, storage allocation, and disk scheduling.
• Protection and Security: Ensuring that access to system resources is controlled and that the system is protected against unauthorized access.