Operating Systems Portfolio

A collection of systems engineering projects built to explore the internals of modern Operating Systems.

This repository serves as a centralized index for my Operating Systems projects. My work focuses on bridging the gap between hardware-specific abstractions and user-facing applications. All projects are written primarily in C and Assembly, focusing heavily on memory management, concurrency, and kernel-level resource allocation.

---

Featured Implementations

1. EGOS MLFQ Scheduler & Custom Shell

An enhanced version of the EGOS-2000 teaching OS natively running on the RISC-V architecture.

• Core Focus: Kernel space programming, Process Control Blocks (PCBs), Timer Interrupts.
• Highlights: Implemented a robust Multi-Level Feedback Queue (MLFQ) preemptive scheduler in the kernel layer to optimize CPU responsiveness, alongside POSIX-like user shell commands (grep, wcl) built entirely from scratch using raw inode and block reading.

2. SimpleScheduler: Round-Robin Daemon

A preemptive, daemonized process scheduler built using POSIX timers and IPC.

• Core Focus: Context Switching (SIGSTOP, SIGCONT), Hardware Timers, IPC Pipes.
• Highlights: Schedules user-submitted processes across NCPU cores using a strict Round-Robin policy. Operates as a background daemon that sleeps natively to conserve CPU cycles, waking only on SIGALRM interrupts to context-switch processes.

3. SmartELFLoader: Dynamic Page-Fault Handler

A custom, lazily-evaluated ELF 32-bit executable loader.

• Core Focus: Virtual Memory, mmap, Signal Handling (SIGSEGV).
• Highlights: Implements lazy loading by intentionally forcing and intercepting segmentation faults. Dynamically allocates memory on-demand in 4KB pages and resumes execution, tracking internal fragmentation metrics.

4. SimpleShell: POSIX-Compliant Unix Shell

A lightweight interactive Unix shell environment built from scratch.

• Core Focus: Process Forking (fork, execvp), Pipe Redirection (dup2).
• Highlights: Natively parses and executes arbitrary pipelines of commands, tracking execution duration and process IDs for every pipeline stage, while safely handling terminal interrupts.

5. SimpleMultithreader: C++11 Concurrency Library

A lightweight, header-only multithreading library abstracting POSIX threads.

• Core Focus: POSIX Threads (pthread), C++11 Lambdas, Iteration Chunking.
• Highlights: Dynamically distributes arbitrary 1D and 2D iteration workloads across numThreads by hooking C++11 lambda functions into bare-metal pthread_create calls without thread pools, and features native microsecond execution profiling.

---

Core Technical Competencies

By completing these projects, I have developed hands-on experience with:

• Languages: C, RISC-V Assembly, Bash
• Concepts: Preemptive Scheduling, Context Switching, Inter-Process Communication, Memory Paging, File System Architectures.
• Tools: GDB, QEMU Emulators, GNU Make, GCC Cross-Compilers.