CPU_Scheduler

Scheduler Simulator — A Time-Driven OS Lab in Code

A simple but insightful CPU Scheduler Simulator built in C that mimics how an Operating System manages CPU time among multiple processes. It supports multiple scheduling algorithms like FCFS (First-Come-First-Serve) and SJF (Shortest Job First) in a tick-by-tick simulation model.

This isn't a full OS kernel. It's a learning-driven simulation where each tick represents a CPU time unit, and every state transition is logged for clarity.

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Features

• Tick-by-tick simulation (1 tick = 1 CPU time unit)
• Multiple Scheduling Algorithms: FCFS, SJF (non-preemptive)
• Modular code structure (clean separation of scheduling logic)
• Command-line algorithm selection
• Handles CPU idle time and I/O-aware jobs (future-ready)
• Metrics tracking: Turnaround Time, Waiting Time, Response Time (WIP)
• Designed for easy extension to RR, SRTF, MLFQ, etc.

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Simulation Model

At each tick:

• Tracks which process is running
• Which are waiting in the ready queue
• Which are doing I/O (extension planned)
• How they move between states

It’s like a time-driven OS lab session – but in C code.

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Input Format

Each process has:

• pid: Process ID (string)
• arrival_time: When it arrives in the system
• CPU burst(s): A sequence of CPU time requirements (e.g., 4,5,6)
• I/O burst(s): (Optional) Time spent doing I/O in between CPU bursts (e.g., 2,3)

Note: Initial version only supports single burst (no I/O interleaving yet).

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Command:

./scheduler --algorithm SJF

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How to Run Build

gcc main.c fcfs.c sjf.c -o scheduler

Run

./scheduler --algorithm FCFS

or

./scheduler --algorithm SJF