Operating Systems and Architecture Quiz

Lesson 3: Introduction of Operating System

• Operating systems control and coordinate hardware use by applications and users.
• Components include hardware (CPU, memory, I/O devices), operating system, and application programs (word processors, compilers, web browsers, database systems). Users (people, machines) interact via application programs.
• Systems can be divided into four components: hardware, operating system, applications, and users.
• Operating systems manage resources and provide a user-friendly interface to computer users while ensuring efficient resource utilization.
• Users want convenient resource access; resource utilization isn't their concern.
• Operating systems are essential for managing the execution of user programs efficiently using hardware resources.
• A computer system is categorized by hardware (CPU, memory, IO devices), operating systems which manages applications, and various applications (word documents, compilers, web browsers, database systems).

Defining Operating Systems

• Operating systems (OS) fulfill diverse roles, from toasters to spacecraft.
• OSes are critical for resource management in general-purpose computers, formerly military-oriented.
• OS definition varies widely; one commonly used description is "everything a vendor ships when you order an OS."
• The kernel is the core program that runs at all times on a computer (part of the OS).
• Everything else is a system program or an application.
• Today's general-purpose OSes also include middleware frameworks that provide extra services to application creators (such as databases, multimedia, graphics).

Computer System Operation

• CPUs and device controllers share a common bus and memory in a computer system.
• Hardware devices and the CPU can work concurrently.
• Device controllers will coordinate data between a device and the main memory.
• A controller notifies the CPU through interrupts; an interrupt is an event that temporarily stops a process.
• Different kinds of interrupt types include various system interrupts, hardware interrupts, etc.
• Interrupts and service routines control data exchange between devices and main memory.

Computer Startup

• A bootstrap program, often firmware (stored in ROM or PROM), initializes the computer during startup or reboot.
• The program loads the kernel of the operating system for execution.
• During interrupt handling, the operating system preserves the state of the CPU by storing registers and program counters.

Interrupt-Driven I/O Cycle

• I/O initialization is performed by device drivers, which handle interactions between the CPU and local buffers.
• The CPU executes checks for interrupts; interrupts are handled by the interrupt handler, which processes data and returns to the interrupted task.

I/O Structure

• When I/O is initiated, control returns to the user program only after I/O completion.

Storage Structure

• Main memory (RAM) provides direct access for the CPU; it is volatile.
• Secondary storage, such as Hard Disk Drives (HDDs) or non-volatile memory devices (NVMs), extends memory capacity.
• Disk surfaces are divided into tracks and sectors, defining how data is organized and accessed.

Storage Management

• Storage is measured in bits (0s and 1s) grouped into bytes, kilobytes (KB), megabytes (MB), gigabytes (GB), terabytes (TB), petabytes (PB).
• Storage hierarchy places increasingly large, but slower storage types lower to minimize access time.

Storage Hierarchy

• Systems organize storage from fastest to slowest, placing high-speed memory closer to the computer processor and slower storage at a distance.

Direct Memory Access (DMA) Structure

• Device controllers can transfer data directly into or out of memory without continuous CPU intervention.

Computer System Architecture

• Modern systems primarily use one general-purpose processor but may also include special-purpose processors.
• Multiprocessor systems, also known as parallel systems or tightly-coupled systems, offer advantages such as increased throughput, greater reliability, and economy of scale.
• Types include symmetric multiprocessing (SMP) where processors share tasks and asymmetric multiprocessing, where tasks are assigned to processors.

Dual-Core Design

• Modern CPUs often contain multiple processor cores.
• This architecture increases performance by parallelizing tasks on different cores.

Non-Uniform Memory Access (NUMA) System

• Memory access times vary depending on the processor and memory location.

Clustered Systems

• Clustered systems consist of multiple systems working together.

Storage Definitions and Review

• The basic unit of computer storage is the bit (a zero or one), which groups to other units like bytes, kilobytes (KB), megabytes(MB), gigabytes (GB), terabytes (TB), and petabytes (PB).

Operating System Operations

• The bootstrap program initializes the system and loads the kernel (the core OS).
• The kernel starts essential system functionalities (daemons) as well as drivers for hardware.
• Hardware interrupts trigger OS to respond when devices require attention.
• Software interrupts signal when software needs a function of the operating system (system call).

Multiprogramming and Multitasking

• In multiprogramming, the CPU switches between multiple programs efficiently, while maintaining execution progress for all active programs.
• Timesharing (multitasking) gives users the impression that programs execute simultaneously through rapid task switching.
• Timesharing allows users to interact with multiple programs while they run, making computer use more interactive.

Dual-mode and Multi-mode Operation

• CPUs or processors typically work in one of two modes: user mode (for user programs) and kernel mode (for OS processes).
• Mode bit is a component of the Central Processing Unit (CPU) that distinguishes kernel execution from user program runtime.
• Access to protected resources is restricted to the kernel mode to maintain system integrity.
• Privileged instructions, those which only run in kernel mode, are essential for accessing critical system resources.
• Systems like virtual machine managers (VMMs) or virtual machines (VMs) allow guest OSs to function more efficiently.

Process Management

• A process is a program in execution, a unit of work within a computer system.
• Process management activities involve creating, deleting, suspending, resuming, synchronizing, and communicating processes.
• Process management aims to coordinate these activities to ensure efficient and productive use of system resources.

File System Management

• File systems give a user-friendly logical view of how files are stored on physical media (e.g., disks), separating storage details from the user interaction.
• File-System organization varies, but methods include sequential and random access.
• File systems manage elements such as files, directories, access control, and storage details.

Mass Storage Management

• Mass storage handles large amounts of persistent data that won't fit in main memory.
• OSes manage storage algorithms, freeing up main memory space when needed.

Cache

• Cache is fast storage that stores copies of data from slower storage (e.g., disk).
• To reduce the number of accesses to slower storage.

Computing Environments

• Computing environments are categorized into different forms of computer usage, including traditional standalone general-purpose computers, client-server architectures where clients request services from servers, and peer-to-peer architectures where all machines act equally.
• Mobile computing environments and cloud computing environments are increasingly commonplace.
• Distributing workloads and managing the use of network resources efficiently are essential to effective computing environments.

Real-time Embedded Systems

• Real-time embedded systems are those used for specific tasks needing quick response time with tight constraints.
• They may use either specialized hardware or special operating systems (e.g., real-time OS).

Free and Open-Source Operating Systems

• Free and open-source operating systems (OSes) are available with source code, enabling users to modify or distribute them, which makes them significantly versatile and widely used.

Distributed Systems

• Distributed systems involve multiple, potentially heterogeneous, computers networked together to access centralized data, processes, and resources.
• Distributed systems give the user a sense that the data, process, and resources are local, but they are actually distributed across a network of machines.

Virtualization

• Virtualization enables the execution of multiple operating systems on a single machine.
• Virtualization provides significant functionality, such as the ability to use a different operating system on a desktop or laptop that would not normally support it.
• Virtualization also allows multiple virtual machines to exist; each virtual machine (VM) can be a complete and different operating system from the host OS that is using virtualization software.

Kernel

• The kernel is the core of the operating system, responsible for managing essential functionalities like process scheduling, memory management, and I/O operations.

I/O Subsystem

• Operating systems provide an interface between users and hardware.
• I/O subsystems are critical for interacting with devices, buffering data transfers, and coordinating communications between a user's programs and storage devices to help efficiently manage input and output functions.

Computing Environments - Client/Server

• Client-server systems distribute tasks between a central server and several clients that request services.
• Client/server systems are commonly used for tasks such as web browsing, database access, and file sharing on a network.

Computing Environments - Peer-to-Peer

• In peer-to-peer systems (P2P), each participant acts as both a client requesting services from other participants and a server providing services to them.
• P2P systems facilitate collaborative file sharing and distribution.

Computing Environments - Cloud Computing

• Cloud computing systems provide computing, storage, and software as services over a network, removing the need for installations and maintenance, and providing wide access using any device.

Test your knowledge of operating systems and computer architecture with this quiz. Explore concepts such as caching, DMA, multiprocessor systems, and the impact of virtualization. Assess your understanding of both theoretical and practical aspects of OS development.