PIXELOKAY COMPUTER SCIENCE LAB / OPERATING SYSTEMS

Operating System Simulator

Step inside the scheduler, trace memory decisions, and test for deadlock—one decision at a time. No installation, accounts or uploads.

◷ CPU scheduling▥ Memory & paging⌁ Resource safety↧ Exportable results

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Systems labInteractive example · not saved

01 / PROCESS MANAGEMENT

See how the CPU chooses.

Single-core scheduling, deterministic tie-breaking and zero context-switch overhead.

Scheduling policy

ALGORITHM

Choose algorithm

Time quantum (RR)

Play speed (ms/tick)

Round Robin gives each ready process up to one quantum before returning it to the queue.

Process workload

1–12

PID	Arrival	Burst	Priority	Actions

All time values are integer ticks. Lower priority numbers run first.

CPU timeline

GANTT

Tick 0

Choose an algorithm and run the schedule.

Process outcomes

METRICS

PID	Start	Finish	Waiting	Turnaround	Response

Compare algorithms

Lower average waiting time is better for this workload, but fairness and responsiveness also matter.

02 / MEMORY MANAGEMENT

Allocate. Free. Compact.

Explore contiguous variable partitions, external fragmentation and page replacement.

Physical memory map

Strip widths are proportional to allocated sizes; gray regions represent free holes.

Allocation table

SELECT FREE

Block	Start	End exclusive	Size (KB)	Action

Page replacement lab

FIFO / LRU / OPTIMAL

Reference string (comma-separated)

Frames

Policy

Compare page policies

Optimal is an offline benchmark that knows future references; real operating systems cannot use it as an online policy.

03 / RESOURCE MANAGEMENT

Safe state ≠ no deadlock.

Explore Banker's safety test, tentative resource requests and an independent wait-for graph.

Resource instance counts

BANKER'S

Available vector (R1,R2,...)

Enter up to four non-negative resource counts.

Each cell uses allocation / maximum claim. Max cannot exceed all instances of that resource.

Try a resource request

WHAT IF

Requesting processRequested instances (R1,R2,...)

Requests beyond Need, Availability, or safety constraints are rejected with a reason.

Safety analysis

ANALYZE

Wait-for graph

SINGLE INSTANCE ASSUMPTION

Waiting process

Waits for

A cycle indicates deadlock only under the stated single-instance/no-unmodeled-dependency assumptions. An unsafe Banker’s state does not prove an existing deadlock.

Private by design · All scenarios and calculations stay in this browser. No backend or imported scripts.

A systems lab built for understanding.

01 / SCHEDULING

Watch decisions change

Compare six dispatch policies against the same workload; step through every execution tick and track waiting, turnaround and response time.

02 / MEMORY

Make fragmentation visible

Allocate and release memory partitions, then compare first, best and worst fit. Explore page faults independently.

03 / DEADLOCKS

Separate risk from certainty

Find a safe sequence with Banker's algorithm, test requests, and inspect genuine cycles in a wait-for graph.

Questions & limitations

Does this simulate a real operating system kernel?

No. It is a deterministic educational model. CPU bursts have no I/O blocking; context-switch overhead, caches, hardware interrupts and virtual memory translation are not modeled.

Is an unsafe Banker's state the same as deadlock?

No. Unsafe means the safety test cannot certify a completion sequence under declared maximum claims; a deadlock may not exist yet.

Are project files uploaded?

No. Imported scenario JSON is validated and processed in your browser. Exports are generated locally. Browser print-to-PDF uses the print dialog, not a PDF upload service.