Summary of Introduction || Chapter 1 || Operating System Concepts || Silberchatz, Galvin &Gagne
Summary of "Introduction || Chapter 1 || Operating System Concepts || Silberchatz, Galvin & Gagne"
Main Ideas and Concepts
- Definition and Role of Operating Systems (OS):
- An OS is a program managing computer hardware and providing an environment for application programs.
- Acts as an intermediary between users and hardware.
- Different OS types optimize for different goals (e.g., mainframes focus on hardware utilization, PCs on usability and performance, mobile OS on user convenience).
- Computer System Organization:
- A computer system consists of hardware, OS, application programs, and users.
- Hardware includes CPU, memory, and I/O devices.
- OS controls hardware and coordinates resource usage among applications and users.
- System structure includes CPUs, device controllers, buses, memory, and interrupts.
- User vs. System View of OS:
- User view: varies by interface (PC, mainframe terminals, workstations, mobile devices).
- System view: OS as resource allocator and control program managing CPU, memory, I/O devices.
- Historical Context and Evolution:
- Early computers were fixed-purpose; evolved to multi-function mainframes.
- Moore’s Law drives increasing functionality and complexity.
- No single complete definition of OS; commonly viewed as the kernel plus system programs.
- Computer System Architecture:
- Single processor systems vs. multiprocessor (multi-core, SMP, asymmetric multiprocessing).
- Multiprocessor advantages: increased throughput, economy of scale, reliability (graceful degradation and fault tolerance).
- Clustered systems: loosely coupled multiple computers linked via networks for high availability or high performance.
- Memory and Storage:
- Memory hierarchy: registers, cache, main memory (RAM), secondary storage (disks), tertiary storage (tape, optical).
- Volatile vs. non-volatile storage.
- Storage measured in bits and bytes; common units KB, MB, GB, TB, PB.
- Virtual memory allows running programs larger than physical memory.
- I/O Systems:
- Device controllers manage specific devices and local buffers.
- Device drivers provide uniform interfaces.
- Interrupt-driven I/O and Direct Memory Access (DMA) reduce CPU overhead.
- Bus and switched architectures affect data transfer concurrency.
- Operating System Functions:
- Multiprogramming: multiple jobs in memory to keep CPU busy.
- Time-sharing (multitasking): rapid CPU switching for interactive user experience.
- Job scheduling, CPU scheduling, memory management, file systems, synchronization, deadlock avoidance.
- Interrupt handling and traps (software interrupts).
- Dual mode operation: user mode vs. kernel mode for protection.
- Privileged instructions only executable in kernel mode.
- Timers prevent programs from monopolizing CPU.
- Process Management:
- Process: active execution of a program.
- Single-threaded vs. multi-threaded processes.
- OS responsibilities: create/delete processes, schedule, synchronize, communicate.
- Memory Management:
- Tracking usage, allocation/deallocation.
- Mapping logical to physical addresses.
- Hardware support required for schemes.
- Storage Management:
- File systems abstract physical storage.
- Managing files, directories, access control.
- Disk management: free space, allocation, scheduling.
- Caching improves performance by storing frequently accessed data in faster storage.
- Computing Environments:
- Traditional desktops/laptops.
- Mobile computing: smartphones/tablets with unique hardware features (GPS, accelerometers).
- Distributed systems: networked computers sharing resources.
- Client-server and peer-to-peer models.
- Virtualization: running OSes as applications within other OSes.
- Cloud computing: delivering computing/storage as services over networks.
- Real-time embedded systems: strict timing constraints for control applications.
- Open Source Operating Systems:
- Source code availability facilitates learning and development.
- Linux, BSD Unix, Solaris, and Mac OS X (Darwin kernel) as examples.
- Benefits: community collaboration, faster bug fixes, educational value.
- History: from early open software to proprietary models, then resurgence via GNU and Linux.
- Licensing: GPL promotes sharing and improvement.
- Many distributions tailored for different uses.
- Summary of OS Study:
- OS manages hardware and provides environment for applications.
- System organization and architecture underpin OS design.
- Multiprogramming and time-sharing maximize CPU utilization.
- Protection via dual mode and privileged instructions is fundamental.
- OS manages processes, memory, storage, and I/O.
- Various computing environments require different OS features.
- Open source movement has greatly expanded access to OS internals and development.
Notable Quotes
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Category
Educational