Operating Systems Quiz

Advanced Operating Systems

• Mahmoud Abou El-Mag Soliman, Department of Computer Science, Faculty of Computers and Artificial Intelligence, Sohag University are the presenter and institution.

Introducing Operating Systems

• A modern computer has multiple processors, main memory, disks, printers, a keyboard, mouse, display, and network interfaces and other input/output (I/O) devices.
• Application programmers do not need to understand every device in detail, which is why operating systems are vital. They provide a simpler model of the computer and manage resources.

Typical Components of a Computer System (Hardware)

• The diagram illustrates a computer's components, including input devices, CPU, main memory (RAM), and secondary storage devices and output devices

Processing Devices: Main Memory (RAM)

• Main memory is the computer's workspace.
• RAM (Random Access Memory) is commonly used as main memory,
• RAM provides quick access to stored data at any location.
• Data in RAM is lost when the computer is turned off.

Main Memory (RAM)

• RAM is like a grid of boxes.
• Each box (cell) has a unique address found by columns and rows.
• The RAM controller uses column and row addresses to access specific cells.

RAM vs. Virtual Memory

• Virtual memory augments RAM by transferring data to disk storage, increasing the address space.
• This allows for running larger or multiple programs simultaneously, as if memory were limitless.

Memory Organization

• A diagram illustrates memory components ordered by access time: registers, cache, main memory, magnetic disks, magnetic tapes.

A program is copied in main memory and then executed

• A program is loaded from secondary storage to main memory.
• The CPU then executes the program in main memory.

The fetch-decode-execute cycle

• The CPU fetches the next program instruction.
• It decodes the instruction to identify the operation.
• The CPU executes the instruction.

RISC and CISC Processors

• RISC (Reduced Instruction Set Computer) processors have fewer, simpler instructions, which are faster to execute and easier-cheaper to build.
• CISC (Complex Instruction Set Computer) processors have more complex instructions and were first developed by Intel.

Programs

• System programs are the interface between application software and the system. These are necessary for the computer to function at all.
• They control system resources and specify paths for application software.
• Application programs respond to user requests and operate on platforms provided by system software.

Introducing Operating Systems

• Computer systems have hardware components (chips, boards, disks, keyboard, monitor) and software.
• The operating system controls the flow between these two.

User View

• Operating system design choices vary depending upon whether the system is for one user or multiple users sharing resources.
• Individual usability or resource utilization are prioritized.

User View

• In networked environments (workstations, servers), OS design must balance both individual usability and efficient resource allocation across multiple users.

User View

• Some computers have limited or no user interaction, focusing solely on automated operation.

System View

• The OS manages computer resources, such as CPU time, memory, file storage space, and I/O devices.
• The OS also acts as a controller for I/O devices and user programs.

Defining Operating Systems

• The OS, mainly the kernel, is a program running constantly.
• Other OS programs support the OS kernel, but aren't always part of the kernel, and user applications are not part of the OS.

Computer-System Operation

• A modern computer has one or more CPUs and various device controllers connected by a shared bus.
• The CPU and controllers share memory, and a memory controller coordinates their access.

Computer-System Operation

• For the computer to begin running (after a reboot), an initial program (bootstrap program) is necessary.
• ROM (read-only memory) contains the bootstrap program which initializes system components.
• The bootstrap program loads the operating system kernel into memory.

Computer-System Operation

• The OS kernel, once running, provides system and user services.
• Some OS services are maintained outside the kernel through system processes (daemons).

Computer-System Operation

• Events are often signaled by interrupts from either hardware or software.
• Interrupts, including special software operations (system calls), signal events to the CPU for the system to handle them appropriately.

Storage Structure

• The CPU only accesses memory.
• Most computers regularly use RAM (random-access memory), often created using DRAM (dynamic random-access memory).

I/O Structure

• A large portion of an OS is dedicated to managing I/O because of the varying nature of devices and the significance in system reliability and performance.

Computer-System Architecture

• Single-processor systems consist of a single CPU, registers, cache, and memory.
• Multiprocessor systems utilize multiple CPUs, with each having its own registers and cache, still sharing the memory.

Computer-System Architecture

• Dual-core designs have two CPUs on a single chip, sharing memory and caches.
• Clustered systems are collections of networked computers (often heterogeneous) with a shared storage area.

Operating-System Structure: Multiprogramming

• Multiprogramming increases CPU utilization by running multiple jobs at once.
• The OS keeps several jobs in memory simultaneously, managing allocation of memory when it gets full

Operating-System Structure: Multiprogramming

• The OS keeps several jobs in memory, allocated from the job pool initially residing on the disk.

Operating-System Structure: Multiprogramming

• The illustration represents memory allocation for a multiprogramming operating system.

Operating-System Operations: Interrupts

• Modern OSs are interrupt-driven.
• Events often signal interrupts, including those caused by errors.

Operating-System Operations: Dual-Mode

• The OS must distinguish between its code and user code for appropriate execution.

Operating-System Operations: Dual-Mode

• Hardware support is critical to distinguish between different execution modes, typically user and kernel modes.

Operating-System Operations: Timer

• The OS uses a timer to prevent user programs from getting stuck in infinite loops or neglecting system calls.

Operating-System Operations: Process Management

• A process is a program in active execution by a CPU.
• This includes user programs (e.g., compilers, word processors).
• System tasks (e.g., sending print output) are also processes.

Operating-System Operations: Process Management

• The OS schedules processes and threads on CPUs, creates and deletes processes, and provides mechanisms for process synchronization and communication.

Operating-System Operations: Memory Management

• Main memory is a shared repository for CPU and I/O devices for readily accessible data.
• The CPU accesses instructions and data stored in main memory.

Operating-System Operations: Memory Management

• The OS keeps records of allocated memory, decides how (and where) to load and unload processes, and allocates and deallocates memory spaces.

Operating-System Operations: Storage Management

• The OS provides a uniform and logical view of storage. This hides physical storage device properties like in logical storage units (files).

Operating-System Operations: Storage Management

• The OS maps files to physical media and manages file access through storage devices.

Operating-System Operations: File Management

• The OS manages creating, deleting files and directories, enabling file manipulation, mapping to storage, and backing up files.

Operating-System Operations: Mass-Storage Management

• Secondary storage (disks) is essential to back up main memory.
• Most modern computers use disks for storing programs and data.

Operating-System Operations: Disk Management

• OSs manage disk free space, allocate storage, and schedule disk operations.

Operating-System Operations: Caching

• The OS uses caching to temporarily store frequently used information in faster storage (like a cache) within main memory for faster access.

Operating-System Operations: I/O Systems

• The OS hides hardware specifics from users.
• It involves components like memory management (including buffering, caching, and spooling), device drivers, and device interfaces.

Operating-System Operations: Protection and Security

• In multi-user systems, access to data, CPU, and resources should be controlled and regulated, granted only to authorized processes.
• A timer prevents processes from monopolizing the CPU.

Computing Environments: Traditional Computing

• In the past, home users had limited connectivity to office systems, using slow modems.
• Today, home access to data/services is facilitated by much faster and cheaper networks.

Computing Environments: Mobile Computing

• Mobile devices (smartphones, tablets) are lightweight and portable, often at the cost of larger screen size and memory capacity.

Computing Environments: Distributed Systems

• Distributed systems comprise networked computers.
• The system resources are shared, improving performance, reliability, and availability.

Computing Environments: Client-Server Computing

• PCs and mobile devices have supplanted terminals for many centralized systems, using web interfaces.
• Client systems send requests to server systems.

Computing Environments: Peer-to-Peer Computing

• Peer-to-peer systems use all nodes as clients and servers without centralized servers.

Computing Environments: Virtualization

• Virtualization allows emulation of one computer system on another.

Computing Environments: Cloud Computing

• Cloud computing is a service-oriented, virtualized network system
• Services, storage, and applications are available to those connected to the network.

Computing Environments: Real-Time Embedded Systems

• Embedded systems are common (car engines, microwaves, etc.)
• They are often specialized with limited user interfaces, prioritizing device management.

Open-Source Operating Systems

• Open-source OSs are available in source code, not compiled binaries. (Linux is a well-known example).