OS Assignment PDF
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This document is an operating systems assignment. It includes questions on topics like the goals and functions of operating systems, multiprogramming, multitasking, and memory management.
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What is Operating System? List the goals of Operating System? An Operating System (OS) is the software that manages hardware and software resources on a computer. It provides essential services that allow other programs to run and users to interact with the computer. Essentially, it\'s the middlema...
What is Operating System? List the goals of Operating System? An Operating System (OS) is the software that manages hardware and software resources on a computer. It provides essential services that allow other programs to run and users to interact with the computer. Essentially, it\'s the middleman between users and the computer\'s hardware. **Goals of an Operating System:** 1. **Resource Management**: Efficiently manage the computer\'s resources such as CPU, memory, storage, and I/O devices. 2. **User Interface**: Provide a convenient and user-friendly interface for users to interact with the system. 3. **File Management**: Organize and manage data storage, allowing for the creation, deletion, and manipulation of files and directories. 4. **Security and Access Control**: Protect system resources and data from unauthorized access and ensure data integrity. 5. **Process Management**: Handle the creation, scheduling, and termination of processes, ensuring efficient execution and multitasking. 6. **Error Detection and Handling**: Detect and handle errors in both hardware and software to ensure reliable and stable system operation. 2\) Compare Multiprogramming and Multiprocessing. Ans: **Multiprogramming** - **Definition**: Multiprogramming is a method where multiple programs are kept in the main memory at the same time, and the CPU executes them by switching between them. - **Objective**: The primary aim is to maximize CPU utilization by ensuring that the CPU always has a task to execute. - **Execution**: Only one program is executed by the CPU at a time, but it switches rapidly between programs to give the illusion of concurrent execution. - **System Complexity**: Simpler compared to multiprocessing systems. - **Usage**: Common in batch processing systems where multiple jobs are managed but only one is executed at any given time. - **Resource Management**: Mainly focuses on managing the CPU time among various jobs to keep it as busy as possible. **Multiprocessing** - **Definition**: Multiprocessing involves the use of two or more CPUs within a single computer system to execute multiple processes simultaneously. - **Objective**: To enhance system performance and reliability by allowing multiple processes to be executed in parallel. - **Execution**: Multiple processes are executed concurrently, with each CPU handling different processes. - **System Complexity**: More complex due to the need for coordination and synchronization between CPUs. - **Usage**: Found in systems requiring high performance, such as servers, mainframes, and scientific computing environments. - **Resource Management**: Manages multiple processors, ensuring efficient allocation and utilization of resources across them. **3) Explain in detail about the following functions of Operating System. i) Process management ii) Memory management** **Ans:** **Process management:** **Process management is a core function of the operating system (OS) that involves handling the processes in a system. Here are some key aspects of process management:** 1. **Process Scheduling: The OS decides which process should run at any given time. This is crucial in a multi-tasking environment to ensure that all processes get fair access to the CPU. Common scheduling algorithms include First-Come-First-Serve (FCFS), Shortest Job Next (SJN), and Round Robin (RR).** 2. **Process Creation and Termination: The OS handles the creation and termination of processes. This involves allocating resources (like memory, I/O devices) to new processes and releasing them once the process terminates.** 3. **Process Synchronization: In environments where processes need to work together or share resources, synchronization ensures that processes do not interfere with each other, which can lead to data corruption or inconsistency. Mechanisms like semaphores and mutexes are used for synchronization.** 4. **Inter-Process Communication (IPC): Processes often need to communicate with each other. IPC mechanisms like message passing, shared memory, and pipes are used by the OS to facilitate this communication.** 5. **Deadlock Handling: The OS must detect and resolve deadlocks, which occur when a set of processes are stuck waiting for resources held by each other, creating a cycle of dependency that prevents any process from proceeding.** **Memory Management** **Memory management involves managing the computer\'s primary memory. This function ensures that each process gets enough memory to execute efficiently and safely. Here are the key tasks involved in memory management:** 1. **Memory Allocation: The OS allocates memory to processes based on their needs. This can be done dynamically (during execution) or statically (at the start of execution). Allocation strategies include fixed-sized partitioning, variable-sized partitioning, and paging.** 2. **Virtual Memory: Virtual memory allows the OS to use disk space as an extension of RAM, providing the illusion of a larger main memory. This technique includes paging and segmentation, enabling processes to run even if they require more memory than physically available.** 3. **Paging: In paging, the OS divides the memory into fixed-sized pages and manages the process\'s memory in units of pages. It helps in efficient and flexible allocation and eliminates external fragmentation.** 4. **Segmentation: Unlike paging, segmentation divides memory into variable-sized segments based on the logical divisions of a program (e.g., code, data, stack). This allows for more natural handling of a program\'s components and can enhance protection and sharing.** 5. **Memory Protection and Isolation: The OS ensures that each process runs in its own memory space, protecting the memory allocated to one process from being accessed or modified by another process. This prevents accidental or malicious interference.** 6. **Garbage Collection: In systems with automatic memory management, the OS periodically reclaims memory allocated to objects that are no longer in use, freeing it for future allocations.** **4) Write a note on different types of Operating Systems.** **Ans:** **1. Batch Operating Systems** - **Description: In a batch operating system, similar jobs are batched together and processed at once. The OS executes these jobs without any user interaction.** - **Example: Early mainframe systems, like IBM\'s Job Control Language (JCL).** **2. Time-Sharing Operating Systems** - **Description: These systems allow multiple users to share system resources simultaneously. The CPU time is divided among the users, giving the illusion that each user has their own dedicated system.** - **Example: UNIX, Multics.** **3. Distributed Operating Systems** - **Description: Distributed OS manages a group of distinct computers and makes them appear as a single computer. Resources are shared and coordinated over a network.** - **Example: Amoeba, Plan 9.** **4. Network Operating Systems** - **Description: Network OS manages data, users, groups, security, applications, and other networking functions over a network. It allows shared access to files and resources.** - **Example: Novell NetWare, Microsoft Windows Server.** **5. Real-Time Operating Systems (RTOS)** - **Description: RTOS is designed for real-time applications that need to process data without buffer delays. They are used in environments where timing is crucial.** - **Example: VxWorks, RTLinux.** **6. Mobile Operating Systems** - **Description: Mobile OS is designed specifically for mobile devices such as smartphones and tablets. They manage hardware and applications to optimize performance and user experience.** - **Example: Android, iOS.** **7. Embedded Operating Systems** - **Description: These OS are designed for embedded systems, which are part of larger machines and dedicated to specific tasks. They are usually compact and efficient.** - **Example: FreeRTOS, Embedded Linux.** **8. Multiprogramming and Multiprocessing Operating Systems** - **Description:** - **Multiprogramming: Supports running multiple programs on a single CPU by rapidly switching between them.** - **Multiprocessing: Utilizes multiple CPUs to execute multiple processes simultaneously.** - **Example:** - **Multiprogramming: IBM OS/360.** - **Multiprocessing: Linux, Windows.** **9. Single-User vs. Multi-User Operating Systems** - **Single-User OS: Designed for one user at a time.** - **Example: MS-DOS.** - **Multi-User OS: Allows multiple users to access a computer system concurrently.** - **Example: UNIX, Linux.** 5\) With a neat sketch, explain Process State Diagram. ans: **Process States** 1. **New**: The process is being created. 2. **Ready**: The process is waiting to be assigned to a processor. 3. **Running**: The process is currently being executed by the CPU. 4. **Waiting (or Blocked)**: The process is waiting for some event to occur (e.g., I/O completion). 5. **Terminated**: The process has finished execution. **State Transitions** - **New to Ready**: The process has been created and is ready to run. - **Ready to Running**: The CPU scheduler has selected the process to be executed. - **Running to Terminated**: The process has completed its execution. - **Running to Ready**: The process has been preempted and put back in the ready queue by the scheduler. - **Running to Waiting**: The process is waiting for an I/O event to complete. - **Waiting to Ready**: The I/O event the process was waiting for has completed, and the process is ready to be executed. Here\'s a neat sketch of the Process State Diagram: 6\) Differentiate i) Scheduler and Dispatcher. ii) Pre-emptive and non-pre-emptive scheduling ans: **i) Scheduler and Dispatcher** **Scheduler** - **Function**: The scheduler is responsible for determining which processes will be given CPU time. It decides the order in which processes will be executed and for how long. - **Types of Schedulers**: - **Long-term scheduler** (Job Scheduler): Decides which jobs or processes are admitted to the system for processing. - **Short-term scheduler** (CPU Scheduler): Selects which of the ready processes will be executed next by the CPU. - **Medium-term scheduler**: Handles swapping processes in and out of memory to manage the degree of multiprogramming. - **Decision Basis**: Based on algorithms that consider priority, process type, and resource requirements. **Dispatcher** - **Function**: The dispatcher is responsible for the actual execution of the process that has been selected by the short-term scheduler. It handles the context switching, which involves saving the state of the currently running process and loading the state of the next process to run. - **Activities**: - Context switching - Switching to user mode - Jumping to the proper location in the user program to restart it - **Execution Time**: The time taken by the dispatcher is called the dispatch latency. This includes the time for context switching and the time to load and run the new process. **ii) Pre-emptive and Non-pre-emptive Scheduling** **Pre-emptive Scheduling** - **Definition**: Pre-emptive scheduling allows the OS to interrupt a running process and assign the CPU to another process. This is useful for ensuring that high-priority processes receive timely CPU access. - **Examples**: Round Robin, Priority Scheduling (if priorities change), and Shortest Remaining Time First (SRTF). - **Advantages**: Better responsiveness and fairness, prevents any single process from monopolizing the CPU. - **Disadvantages**: Requires more complex OS algorithms, potential for higher overhead due to frequent context switching. **Non-pre-emptive Scheduling** - **Definition**: In non-pre-emptive scheduling, once a process has been assigned the CPU, it runs to completion or until it voluntarily yields the CPU (e.g., by waiting for I/O). - **Examples**: First-Come, First-Serve (FCFS), Shortest Job Next (SJN), Priority Scheduling (if priorities are fixed). - **Advantages**: Simpler implementation, less overhead as context switching only occurs when a process terminates or waits for I/O. - **Disadvantages**: Can lead to poor responsiveness and inefficient CPU utilization if long processes block shorter ones. 7\) What are the three major activities of an operating system with regard to memory management? ans: - - - - - - 10)What will be output of following code? Explain your answer. int main( ) { int i=0; int pid; for(i=0;i\