About the Book ===================== This book grew out of an effort that began nearly fifteen years ago with George K. Thiruvathukal, the lead editor, students in his research laboratory, and faculty colleagues. Dr. Thiruvathukal has been teaching operating systems and distributed systems since the early 1990s, when he taught Operating System Design and Implementation at the Illinois Institute of Technology while completing his PhD. The motivation for the book is practical. Many operating systems textbooks are encyclopedic. They cover a large number of topics, but they often spend less time on the implementation ideas that students need in order to understand how operating systems are actually built. This book focuses on the ideas that generally made it into modern operating-system implementation, backed by coding examples that we hope actually work. The book is designed as a companion for instructors who want to give students a concise introduction to operating systems and the practice of learning C programming without requiring an expensive textbook. C is not the only systems language, and modern practice is increasingly interested in Rust, Go, and other options. We introduce those ideas gradually where they fit. Still, C remains useful because it exposes pointers, memory layout, calling conventions, system calls, and hardware-facing details with relatively little abstraction. In that sense, it can be thought of as a portable assembly language. We also expect C to remain important in embedded systems, accelerators, firmware, device drivers, and hardware contexts where direct control still matters. Approach ---------- The chapters are meant to be read alongside code. The goal is not to catalog every operating-system feature. The goal is to explain the core ideas clearly enough that students can connect the concept, the system call or data structure, and the behavior they observe when running a program. Most examples are written in C, with C++ used where it does not distract from the systems idea. Some examples and case studies use other languages, but the main programming model is deliberately close to the machine. Book Organization ------------------ Introduction ^^^^^^^^^^^^ The :doc:`Introduction ` chapter gives historical context. It traces operating systems from early batch systems through UNIX, personal computers, and modern systems. Systems and Discrete Math Recap ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The :doc:`Systems and Discrete Math Recap ` chapter reviews background material students are expected to know before the main operating-systems chapters. It includes Boolean logic, binary numbers, bit operations, memory layout, pointers, and small C examples. Introduction to Processes ^^^^^^^^^^^^^^^^^^^^^^^^^ The :doc:`Introduction to Processes ` chapter explains processes, address spaces, process creation, ``fork()``, ``exec()``, and related process-control ideas. Files and I/O ^^^^^^^^^^^^^ The :doc:`Files and I/O ` chapter introduces the UNIX file abstraction. It explains file descriptors, regular files, directories, devices, pipes, sockets, and the common operations used to work with them. Process/Thread Scheduling ^^^^^^^^^^^^^^^^^^^^^^^^^ The :doc:`Process/Thread Scheduling ` chapter explains how an operating system decides what runs next. It covers user mode, kernel mode, interrupts, context switching, scheduling goals, and scheduling policies. Mutual Exclusion ^^^^^^^^^^^^^^^^ The :doc:`Mutual Exclusion ` chapter introduces shared state, critical sections, atomicity, locks, semaphores, monitors, and other synchronization mechanisms used to make concurrent programs correct. Deadlock ^^^^^^^^ The :doc:`Deadlock ` chapter explains how threads can become stuck waiting for one another. It covers the dining philosophers problem, lock graphs, deadlock conditions, and practical ways to avoid deadlock. IPC Topics ^^^^^^^^^^ The :doc:`IPC Topics ` chapter covers interprocess communication. It compares pipes, named pipes, signals, shared memory, memory-mapped files, UNIX domain sockets, Solaris doors, and network sockets. Virtual Memory ^^^^^^^^^^^^^^ The :doc:`Virtual Memory ` chapter explains the kernel side of memory management. It covers address spaces, MMUs, page tables, page replacement, demand paging, and case studies drawn from kernel memory systems. Userland Memory Management ^^^^^^^^^^^^^^^^^^^^^^^^^^ The :doc:`Userland Memory Management ` chapter explains how language runtimes and libraries manage memory inside a process. It covers heaps, allocation, garbage collection, smart pointers, reference counting, and stack allocation. Storage and Devices ^^^^^^^^^^^^^^^^^^^ The :doc:`Storage and Devices ` chapter introduces storage hardware and the operating-system policies used to manage it. It covers device interfaces, buses, disks, flash storage, disk scheduling, RAID, and storage services. Implementing Files and Folders ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The :doc:`Implementing Files and Folders ` chapter explains how filesystems represent files, directories, metadata, free space, and paths. It also includes case studies of filesystem designs and research systems. Book Index ^^^^^^^^^^ The :doc:`Book Index ` provides index entries for important terms, system calls, abstractions, and examples used throughout the book. Key Download Links ------------------- This book automatically builds and deploys using GitHub Actions (a continuous integration system). All commits trigger a rebuild of the book and, if successful, a deployment to GitHub pages. Book Web Site `os.cs.luc.edu `__ Book PDF (Latest Release) `github.com/LoyolaChicagoBooks/operatingsystems/releases/latest/download/OperatingSystems.pdf `__ Book Source Code `github.com/LoyolaChicagoBooks/operatingsystems `__ Book Info ---------- This book is hosted on GitHub Pages. It is written using the delightful Python Sphinx documentation tool. In addition, we use the Sphinx Book Theme. You can checkout the book from the Book Source Code and build it yourself. This could be useful if you wish to help us correct bugs/errors by issuing a pull request. While we welcome pull requests, we ask that you make sure your request can build successfully, especially if it requires changes to the book and any of the accompanying repositories. Book Examples -------------- Although we write most examples in 100% pure C code, there are occasions where we mix C and C++, especially if the C++ code does not get in the way of the systems pedagogy. That said, we also have some *emerging* examples in Go, Java, C#, Python, and Scala, since we are constantly trying to find a way to apply high-level langauges and software engineering ideas to systems programming. While the most promising we have found so far is Go, we don't think it is going to fully displace C/C++ for the foreseeable future. Nevertheless, early testing has shown some good performance! The future of systems remains bright! C/C++ Examples `github.com/SoftwareSystemsLaboratory/systems-code-examples `__ Java Examples `github.com/LoyolaChicagoCode/hpjpc-source-java `__ Java Multicast Example `github.com/gkthiruvathukal/multicast-java `__ Contact -------- If you have any questions, please contact gkt@cs.luc.edu. George K. Thiruvathukal acts as the maintainer and lead author of this book.