# PandOS

**[Shahir Ahmed](https://github.com/Shahir-47) and [Boosung Kim](https://github.com/BoosungKim)**  
Operating Systems Project – PandOS Kernel for uMPS3  

## Overview

PandOS is a custom operating system developed for the **uMPS3** emulator, a 3000 RISC architecture simulator. This project implements key OS functionalities such as:

- **Time-sharing & Multiprogramming** – Running multiple processes concurrently.
- **Process Scheduling** – Using the **round-robin** algorithm for CPU time allocation.
- **Device Interrupt Handling** – Managing hardware interaction through interrupts.
- **System Call Management** – Supporting I/O, process creation, and termination.
- **Trap Handling** – Managing runtime errors to maintain system stability.
- **Deadlock Detection** – Preventing system-wide resource locks.
- **Virtual Memory with Paging** – Enabling efficient memory management via **TLB paging**.

For a more detailed explanation of the project, see the [Technical Report](./PandOS-Implementation-Report.pdf).

## Implementation Phases

### **Phase 1: Queue Management**
- Implemented **Process Control Blocks (PCB)** and **Active Semaphore Lists (ASL)**.
- Designed **linked list structures** for process scheduling and synchronization.

### **Phase 2: Kernel Development**
- Added **round-robin scheduler**, **interrupt handlers**, and **system calls** for I/O and process management.
- Integrated **passeren (P) / verhogen (V) operations** for mutual exclusion.

### **Phase 3: Support Level**
- Implemented **paging and virtual memory** with **TLB address translation**.
- Enabled **eight concurrent user processes** with swap pool management.

## Setup & Compilation

### **1. Compile the PandOS Kernel**
Navigate to the `pandos/phase3` directory and run:

```sh
make
```
To clean up previous builds:

```sh
make clean
```

### **2. Set Up uMPS3 Emulator**
1. Launch uMPS3:  
   ```sh
   umps3
   ```
2. Create a new machine configuration:
   - **Set directory** to `pandos/phase3`
   - Adjust general settings:  
     - **TLB Size**: 32  
     - **TLB Floor**: `0x80000000`  
     - **RAM Size (Frames)**: 128  

3. Configure Flash Drives:  
   - Assign each flash drive to a corresponding user process (see [Technical Report](./PandOS-Implementation-Report.pdf) for details).

4. Enable all 8 terminals under the **"Terminals"** tab.

### **3. Run PandOS**
1. Power on the emulator.
2. Open **Windows > Terminal 0-7** to observe output from all eight user processes.
3. Click the **Run (▶) button**.

## Testing
To test **swapStress.c**:
1. Modify `Makefile` in `pandos/phase3/resources/testers`:
   - Replace `terminalTest5.umps` with `swapStress.umps`
2. Recompile and run:

```sh
make
umps3
```

## Reflection
This project deepened our understanding of **process synchronization**, **virtual memory**, and **low-level OS design**. Implementing **paging with TLB** and handling **device interrupts** provided valuable experience in kernel development.

## **Technical Report**
For a full breakdown of implementation details, see [PandOS-Implementation-Report.pdf](./PandOS-Implementation-Report.pdf).

## **Authors**  
[Shahir Ahmed](https://github.com/Shahir-47) & [Boosung Kim](https://github.com/BoosungKim)