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Advanced Operating System Concepts

• Operating systems act as intermediaries between users and computer hardware.
• They manage hardware resources, execute user programs, and make the system convenient to use efficiently.
• Computer systems comprise hardware, operating system, application programs, and users.
• Hardware includes CPU, memory, and I/O devices.
• Operating systems manage and coordinate the use of hardware resources among applications.
• Applications are programs that leverage system resources, like word processors, browsers, and databases.
• Users include people and systems interacting with the computer.

Operating System Functions

• Operating systems manage resources, ensuring fair and efficient resource allocation.
• They control program execution, managing errors and preventing misuse.
• Operating systems are responsible for resource allocation and control.

Operating System Definition

• The OS is a resource allocator and a control program.
• The kernel is the one program running continuously.
• Other components are either system programs (part of the OS) or application programs.

Computer Startup

• A bootstrap program, often firmware, initializes the system and loads the OS kernel.

Computer System Organization

• CPUs, device controllers, and memory are interconnected via a common bus.
• Concurrent execution of CPUs and devices occurs.
• I/O devices operate concurrently with the CPU.

Common Functions of Interrupts

• Interrupts transfer control to interrupt service routines.
• They involve an interrupt vector, containing addresses of all service routines.
• Software-generated interrupts include exceptions and user requests.

Interrupt Handling

• The operating system preserves the CPU state and determines the interrupt type.
• Polling or vectored systems determine appropriate actions for different interrupts.

Storage Definitions

• The fundamental storage unit is a bit, with values 0 or 1.
• A byte is eight bits, the smallest convenient storage unit on most computers.
• Words are computer-architecture-dependent storage units, typically comprising one or more bytes.
• Computer storage measurements use units like KB (kilobytes), MB (megabytes), GB (gigabytes), etc.

Storage Structure

• Main memory provides direct, random access for the CPU, usually volatile,
• Secondary storage extends main memory with non-volatile capacity, like hard disks.
• Solid-state disks are faster than hard disks and nonvolatile Solid-state storage technologies are improving.

Storage Hierarchy

• Storage systems are organized in a hierarchy based on speed, cost, and volatility.
• Caching, copying information to faster storage, improves performance.
• Device drivers provide a uniform interface between storage controllers and the OS kernel.

Storage-Device Hierarchy

• Various storage devices are in the hierarchy, from registers to tapes.

Caching

• Caching improves performance by copying information to faster storage.
• The cache is checked first, retrieving information directly from cache when available.

Direct Memory Access (DMA)

• High-speed I/O devices use DMA to transfer data directly to main memory without CPU intervention.

Modern Computer Operation

• I/O operations involve device drivers, controllers, and interrupts.

Computer System Architecture

• Single-processor systems are common but multiprocessor systems (also parallel systems, tightly connected) are increasingly important, offering advantages such as increased throughput, economy of scale, and increased reliability.
• Two types of multiprocessor systems are asymmetric and symmetric multiprocessing.

Symmetric Multiprocessing (SMP)

• Symmetric multiprocessing systems use similar architecture to share tasks efficiently.

Clustered Systems

• Clustered systems group multiple systems together. This improves reliability (asymmetric/symmetric clustering), high-availability, and high performance.