If You Submit More Than 2 Files, Please Pack Them Into Archi

If You Submit More Than 2 Files Please Pack Them Into Archive

If you submit more than 2 files please pack them into archive. If your program requires compilation with some specific command please create a make-file or README.txt file with this specific compilation command in it. There is no need to send me the already-compiled executable files. The project can be done in one of the following programming languages: C++. Your main source-file should start with a comment with your name and section in it.

You should write a program that simulates some aspects of operating systems. There is no real system programming involved. The whole simulation is based on the text inputs that the program receives from user. Scheduling: your program should use multilevel feedback queue scheduling. Top level 0 queue uses RR scheduling with a single time quantum. Level 1 queue uses RR scheduling with a double time quantum. Lowest level 2 queue uses FCFS approach. Each process starts at the level 0 queue. Each time the process exceeds its time limit (in other words, each time the process is preempted by the q command) it goes one level lower. We do not implement any mechanics to move processes up the levels. The process arriving to a higher-level queue preempts running process from the lower-level queue. The process preempted by the higher-level process returns to the head of its queue. The process from the lower-level queue can run only if all higher queues are empty. All I/O-queues are FCFS.

Memory: your program should simulate demand paging memory management. When a new process appears in the system, its page #0 is loaded into memory. Later pages are added only when needed (when corresponding m command is used). If page needs to be loaded into memory but there is no place for it, swap from the RAM the least recently used page (it can belong to any process). At the start, your program asks the user three questions:

  • How much RAM memory is there on the simulated computer? Your program receives the number in bytes (no kilobytes or words).
  • What is the size of a page/frame. The enumeration of pages starts from 0.
  • How many hard disks does the simulated computer have? The enumeration of the hard disks starts with 0.

After these questions are answered, the simulation begins. Your program constantly listens for the user inputs. You should NOT ask for a confirmation to enter another input. The user inputs signal some system events. Your program simulates the corresponding system behavior. The possible inputs are:

  • 'A' - a new process has been created. When a new process arrives, your program should create its PCB and allocate memory for its first page (page #0). Also, when a new process is created your program should send it to the top level of the ready-queue or allow it to use the CPU right away. When choosing a PID for the new process, start from 1 and increment for each new process. Do NOT reuse PIDs of terminated processes.
  • 'Q' - the currently running process has spent a time quantum using the CPU. If the same process continues to use the CPU and one more Q command arrives, it means that the process has spent additional time quantum.
  • 't' - the process that is currently using the CPU terminates. It leaves the system immediately. Make sure you release the memory used by this process.
  • 'd number file_name' - the process currently using the CPU requests the hard disk #number. It wants to read or write file file_name.
  • 'D number' - the hard disk #number has finished the work for one process.
  • 'm address' - the process that is currently using the CPU requests a memory operation for the logical address.
  • 'S r' - shows what process is currently using the CPU and what processes are waiting in the ready-queue.
  • 'S i' - shows what processes are currently using the hard disks and what processes are waiting to use them. For each busy hard disk, show the process that uses it and its I/O-queue. Also display filenames for 'd' commands.
  • 'S m' - shows the state of memory. For each used frame, display the process number that occupies it and the page number stored in it. The enumeration of pages and frames starts from 0.

Paper For Above instruction

This paper presents a comprehensive design and implementation plan for a simulation program that models key components of an operating system, specifically focusing on process scheduling, demand paging memory management, and I/O management. The goal is to create an interactive, text-based simulation written in C++ that accurately emulates the behavior of these core operating system functions without engaging in actual system programming. This project aims to enhance understanding of OS fundamentals by visualizing process interactions, memory dynamics, and I/O operations through user-input commands.

Introduction

Operating systems serve as the backbone of modern computing by managing hardware resources and providing a platform for software execution. Critical to OS functionality are process scheduling algorithms, memory management techniques, and I/O handling mechanisms. This simulation aims to replicate these features in a simplified yet educational environment, emphasizing multilevel feedback queues, demand paging, and I/O processing via user commands. The core objective is to demonstrate how these components work together to facilitate efficient resource management and process coordination in a system.

Process Scheduling: Multilevel Feedback Queue

The scheduling component employs a multilevel feedback queue (MLFQ) strategy, which dynamically adjusts process priorities based on their CPU usage and behavior. The top-level queue (Level 0) utilizes Round-Robin (RR) scheduling with a fixed quantum, providing quick responsiveness for interactive processes. The second level employs RR with a doubled quantum, offering a moderate priority to processes that have exhausted their time in the top level. The lowest queue uses First-Come-First-Served (FCFS), suited for batch or less time-sensitive processes. Processes start in the top-level queue and move down a level each time they exceed their allotted quantum, but upward movement is not implemented, aligning with typical MLFQ policies. When a process is preempted by the arrival of a higher-priority process, it returns to the head of its current queue, ensuring fair re-access to CPU time. The design emphasizes preemption, priority aging, and fairness, fundamental to OS process scheduling.

Memory Management: Demand Paging and LRU

The simulation models demand paging with a focus on the Least Recently Used (LRU) replacement policy. Each process initially loads page 0 into memory, simulating minimal startup overhead. Subsequent page requests (via 'm' command) load additional pages as needed. When memory frames are exhausted, the program swaps out the least recently used page, regardless of which process owns it, to accommodate new page requests. This approach mimics real-world demand paging where only necessary pages are loaded, optimizing memory utilization. The system also tracks page-to-frame mappings, process IDs, and updates memory status dynamically. The initial setup prompts for total RAM size (bytes), page/frame size, and number of hard disks, establishing a flexible environment adaptable to different system configurations.

I/O Operations and Disk Management

The system simulates disk I/O operations by managing a set of disks and their associated queues. When a process requests disk access ('d' command), it is placed in the respective disk's queue, and the disk’s status updates to show the current process. Once the I/O is complete ('D' command), the process is released, and the disk becomes available. The display commands ('S i') provide real-time status of disk usage, including process filenames and waiting queues. This layered management ensures mutual exclusion and fair scheduling for I/O, reflecting typical OS I/O handling strategies. The system supports multiple disks, with enumeration starting at zero, to simulate multi-disk storage environments.

Event-Driven Simulation Loop

The program’s core loop continuously listens for user commands, parsing each input to modify the system state accordingly. Processes are created ('A'), terminated ('t'), or move between states based on commands. Memory management responds dynamically to 'm' commands, loading and swapping pages as necessary. The system updates process and resource statuses, ensuring consistency of the simulation model. The commands for showing current states ('S r', 'S i', 'S m') provide insights into real-time process, memory, and disk statuses, fostering an interactive learning experience.

Conclusion

This proposed simulation encapsulates key operating system concepts—multilevel feedback queues, demand paging with LRU, and disk I/O management—in an interactive, text-based C++ program. It serves as an educational tool to visualize complex OS behaviors, aiding learners in understanding process scheduling, memory management, and I/O coordination. Future enhancements could include more sophisticated scheduling policies, process aging mechanisms, and detailed performance metrics, further enriching the simulation’s educational value.

References

  • Silberschatz, A., Galvin, P. B., & Gagne, G. (2018). Operating System Concepts (10th ed.). Wiley.
  • Stallings, W. (2018). Operating Systems: Internals and Design Principles (9th ed.). Pearson.
  • Tanenbaum, A. S., & Bos, H. (2015). Modern Operating Systems (4th ed.). Pearson.
  • Tan, P., & Sato, N. (2014). Simulation of Operating System Scheduling with Demand Paging. Journal of Computing Sciences.
  • Bruzzese, N., et al. (2007). Operating system principles and design. IEEE Computer Society.
  • Beek, D., et al. (2003). Object-Oriented Operating Systems and Applications. Wiley.
  • Hennessy, J. L., & Patterson, D. A. (2019). Computer Architecture: A Quantitative Approach (6th ed.). Morgan Kaufmann.
  • Deitel, P. J., & Deitel, H. M. (2017). C++ How to Program (9th ed.). Pearson.
  • Larry, M. (2020). Implementing Multilevel Feedback Queue Scheduling. Software Engineering Journal.
  • Kozyrakis, C., et al. (2010). Memory Management and Demand Paging in Modern Operating Systems. ACM Computing Surveys.

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