Jawaharlal Nehru Technological University Hyderabad B.Tech III OPERATING SYSTEMS Previous Question Paper (October - 2020 - R16)

Computing environments have evolved significantly to meet diverse processing needs. The primary types include:

• Personal Computing: Systems designed for individual use, such as PCs and laptops, focusing on user convenience and responsiveness.
• Time-Sharing Systems: Environments where multiple users share a single CPU through rapid context switching, allowing interactive use of the system.
• Distributed Systems: A collection of physically separate, heterogeneous computer systems networked together to provide users with access to various resources, improving reliability and scalability.
• Client-Server Systems: A model where servers provide resources or services (like file storage or databases) to clients that request them over a network.
• Cloud Computing: A delivery model that provides computing services (servers, storage, databases, software) over the internet, allowing on-demand access and resource pooling.
• Embedded Systems: Specialized computing environments designed for specific tasks within larger mechanical or electrical systems, often operating under real-time constraints.

Memory management is the functionality of an operating system that handles or manages primary memory and moves processes back and forth between main memory and disk during execution. Its primary objectives are to ensure efficient CPU utilization and provide processes with sufficient memory to execute.

Key aspects of memory management include:

• Logical vs. Physical Address Space: The OS maps logical addresses generated by the CPU to physical addresses in RAM. This abstraction allows programs to run without knowing their exact location in hardware.
• Swapping: A process can be swapped temporarily out of main memory to a backing store and then brought back into memory for continued execution, allowing the system to handle more processes than physical memory can hold.
• Contiguous Memory Allocation: Memory is divided into partitions. Each partition contains exactly one process. Techniques like first-fit, best-fit, and worst-fit are used to allocate memory blocks.
• Paging: A memory management scheme that eliminates the need for contiguous allocation of physical memory. The physical memory is broken into fixed-sized blocks called frames, and logical memory is broken into blocks of the same size called pages.
• Segmentation: A memory management scheme that supports the user view of memory, where a program is viewed as a collection of segments (e.g., main program, functions, stack) rather than a linear array of bytes.
• Virtual Memory: An extension of physical memory that allows the execution of processes that are not completely in memory. It enables large programs to run on systems with limited physical RAM by loading only the required parts into memory.