CPU Scheduling Simulator

This project is a CPU scheduling simulator that supports multiple scheduling algorithms. It includes various queues for job management and maintains a Gantt chart to visualize the scheduling process.

Typedef

Process

typedef struct {
    int pid;                // Process ID (0 to n-1)
    int CPUburst;           // Total CPU burst time
    int IOburst;            // Total I/O burst time
    int IOstart;            // After 'IOstart' CPU burst time, I/O operation started
    int arrival;            // Arrival time of process
    int tmpArrival;         // Recent time when process goes to readyQ
    int priority;           // Priority of process
    int CPUburst_remain;    // Remaining CPU burst time
    int IOburst_remain;     // Remaining I/O burst time
    int timequantum;        // Remaining time quantum of process
    int waitingTime;        // Waiting time of process
    int turnaroundTime;     // Turnaround time of process
} Process, *pProcess;

Variables

• job[]: Stores processes after creation.
• jobQ[]: Job queue for each scheduling (initialized at the start of each scheduling).
• readyQ[]: Ready queue for each scheduling (initialized at the start of each scheduling).
• waitQ[]: Waiting queue for each scheduling (initialized at the start of each scheduling).
• terminateQ[]: Queue for terminated processes (initialized at the start of each scheduling).
• ganttChart[]: Gantt chart for each scheduling (initialized at the start of each scheduling).

Note: Every queue is a circular queue. The degree of multiprogramming is 100.

Functions

• init_queue: Resets the queue.
• init_jobQ: Resets jobQ and copies job to jobQ.
• init_ganttChart: Resets the Gantt chart.
• add_ganttChart: Adds an entry to the Gantt chart.
  • If the same process, does nothing.
  • If a different process, updates the end time, starts a new process, and time.
  • If all processes are terminated, updates the end time.
• auto_create_process: Automatically (randomly) creates processes.
• create_process: Creates processes manually as specified by the user.
• IOProcess: All processes in waitQ decrease their I/O burst time.
  • If I/O burst time reaches 0, the process moves to readyQ.
• FCFS_scheduling: Schedules processes using the FCFS algorithm.
• SJF_scheduling: Schedules processes using the SJF algorithm.
• SRJF_scheduling: Schedules processes using the SJF algorithm with preemption.
• priority_scheduling: Schedules processes using the priority algorithm.
• preemptive_priority_scheduling: Schedules processes using the priority algorithm with preemption.
• RR_scheduling: Schedules processes using the round-robin algorithm.
• preemptive_priority_RR_scheduling: Schedules processes using the priority algorithm with preemption.
  • If processes have the same priority in readyQ, schedules using the round-robin algorithm.

Scheduling Algorithms

• FCFS (First-Come, First-Served)
• SJF (Shortest Job First)
  • Non-preemptive
  • Preemptive
• Priority
  • Non-preemptive
  • Preemptive with FCFS
  • Preemptive with Round Robin
• Round Robin

How to Run

1. Open Oracle VM VirtualBox.

2. Log in to the OS-tutorial1.

3. Open SSH using VSCode.

4. Compile the simulator:

   gcc -o CPU_simulator CPU_simulator.c

5. Run the simulator:

   ./CPU_simulator

6. Follow the prompts:

   • Input the number of processes.
   • Input the time quantum.
   • Input the mode:
     • 0: Create processes manually.
     • 1: Create processes automatically (randomly).

Output

• Prints all created processes.
  • If I/O operation: After n CPU burst time, starts I/O operation.
    • Example: CPU burst time: 3 (after 2 I/O start), IO burst time: 5
      • Execution: CPU 2 -> I/O 5 -> CPU 1
• Displays the Gantt chart, average waiting time, turnaround time, and CPU utilization for each scheduling.