CSC 221 Operating Systems Overview

Course Information

• The course is CSC 221 : Operating Systems at Egypt-Japan University of Science and Technology.
• The instructor is Dr. Ahmed Hamdy Ahmed Arafa, who is part of the CSIT Programs and CSE Dept, Faculty of Electronic Engineering, Menoufia University.
• Contact information for Dr. Arafa is [email protected], LinkedIn: https://www.linkedin.com/in/ahmed-h-arafa/, and phone: +201009855673.

Grading Breakdown

• Course Prerequisite: CSE 214 (Computer Organization)
• Class Work: 15% (45 degrees), including lectures, assignments, and quizzes
• Mid-Term Exam: 30% (90 degrees), written exam format
• Lab Evaluation: 15% (45 degrees), including lab evaluations and a project
• Final Exam: 40% (120 degrees), 3-hour written exam
• Total: 100% (300 degrees)

Course Content Overview

• Overview of Operating Systems
• Operating System Principles
• Concurrency
• Scheduling and Dispatch
• Memory Management
• Security and Protection
• Virtual Machines
• Device Management
• File Systems
• Real-Time and Embedded Systems
• Fault Tolerance
• System Performance Evaluation
• The reference textbook is "Avi Silberschatz, Peter Galvin, and Greg Gagne, Operating System Concepts – 10th Edition".

Introduction to Operating Systems (Chapter 1)

• Key topics include what operating systems do, computer-system organization and architecture, operating system operations, resource management, security and protection, virtualization, distributed systems, kernel data structures, computing environments, and free/libre and open-source operating systems

Objectives of Studying Operating Systems

• Describe the general computer system organization and the role of interrupts.
• Understand components of a modern, multiprocessor computer system.
• Illustrate the transition between user mode and kernel mode.
• Discuss how operating systems are used in various computing environments.
• Provide examples of free and open-source operating systems.

Defining an Operating System

• An operating system completes needed functionalities.
• What it does for cars, airplanes, printers, washing machines, toasters, compilers, etc.
• Operating system goals include executing user programs, solving user problems, providing convenience, and efficient hardware use.

Computer System Structure Components

• Hardware provides basic computing resources like CPU, memory, and I/O devices.
• The operating system controls and coordinates hardware use among applications and users.
• Application programs define how system resources solve user computing problems, including word processors, compilers, web browsers, database systems, and video games.
• Users include people, machines, and other computers.

Operating System Perspectives

• Users prioritize convenience, ease of use, and performance, not caring about resource utilization.
• Shared computers, such as mainframes or minicomputers, require the OS to keep all users happy.
• The operating system is a resource allocator and control program ensuring efficient hardware utilization to manage user program execution.
• Dedicated systems like workstations offer dedicated resources but may share server resources.
• Mobile devices balance resource constraints, usability, and battery life with mobile interfaces like touch screens.
• Embedded computers in devices and automobiles, often run without user intervention.

Defining Operating Systems

• The term OS covers many roles, influenced by designs and uses.
• Operating systems are present in various devices, from toasters to spacecraft.
• Born for military fixed-use computers and evolved for more general resource management.

Operating System Definition Clarification

• No single OS definition is universally accepted.
• One definition is "Everything a vendor provides when you purchase an operating system.".
• The kernel is "the one program running at all times", a core component of the OS.
• The rest is either a system program (part of the OS but not the kernel) or an application program (not of the OS).
• Modern OSes include middleware that provides additional services like databases and multimedia capabilities.

Computer System Organization

• Computer-system operation includes one or more CPUs and device controllers connected through a common bus that shares memory.
• Concurrent execution of CPUs and devices competing for memory cycles takes place.

Computer-System Operations

• I/O devices and the CPU can execute concurrently.
• Each device controller manages a specific device type and has a local buffer.
• Device controllers manage it using an OS device driver.
• The CPU transfers data between the main memory and local buffers.
• I/O transfers data from the device to the local controller buffer.
• The device controller signals the CPU when it finishes its operation using an interrupt.

Common Interrupt Functions

• Interrupts transfer control to the interrupt service routine through the interrupt vector, containing the addresses of service routines.
• Interrupt architecture must save the address of the interrupted instruction.
• A trap or exception is a software-generated interrupt triggered by errors or user requests.
• Operating systems are interrupt-driven.

Interrupt Handling

• The OS preserves the CPU state by storing registers and the program counter.
• Determines which type of interrupt has occurred.
• Separate code segments determine the action to take for each interrupt.

I/O Structure Methods

• One method involves control returning to the user program only after I/O completion.
• Another method gives control back to the user program without waiting for I/O completion.

I/O Structure Details and System Calls

• Post I/O start, user program control happens upon I/O completion.
• A wait instruction idles the CPU until the next interrupt.
• There is a wait loop for memory access contention.
• Only one request is outstanding, which means no simultaneous processing.
• Post I/O start, control reverts to the user program without awaiting I/O completion.
• A system call requests the OS for the user process to await I/O completion.
• A device-status table documents every I/O device with its type, state and address.
• The OS checks up the I/O device table status and modifies table entries to include interrupts.

Storage Structures

• Main memory is the only storage the CPU can directly access, using random access.
• Main memory is typically volatile.
• DRAM is its common form.
• Secondary storage extends main memory and offers large, nonvolatile capacity.

HDDs vs NVHM

• Hard Disk Drives (HDDs) utilize rigid platters overlaid with magnetic recording.
• Logically, the disk surface divides into tracks that subdivide into sectors.
• The disk controller governs the logical interaction of the devices and the computer.
• Solid-state Non-Volatile Memory (NVM) devices are faster and are nonvolatile.
• NVM technologies are gaining traction with more capacity and performance, and lower price points.

Storage Definitions and Notation Review

• The basic unit of computer storage is the bit which stores a 0 or 1.
• A byte is 8 bits and forms the smallest chunk of storage handled by most computers.
• A word is the native unit of data for a computer architecture, consisting of one or more bytes.
• Kilobyte (KB) is 1,024 bytes, Megabyte (MB) is 1,0242 bytes, Gigabyte (GB) is 1,0243 bytes, Terabyte (TB) is 1,0244, and Petabyte (PB) is 1,0245 bytes.

Storage Hierarchy

• Storage systems are organized by speed, cost and volatility.
• Caching involves copying data into quicker storage units, where main memory doubles as secondary storage cache.
• Each device controller uses an I/O Device Driver to manage I/O and offer uniform interface.

Understanding Data Migration

• Multitasking setups must track the variable no matter is location in the memory setup.
• Multiprocessor system must provide cache coherency so all CPUs have the latest data.
• The situation is greatly complicated more in distributed environments.
• Copies of data can exist that necessitate solutions as those described in Chapter 19.

Key I/O Subsystem Responsibilities

• The purposes of an OS includes hiding hardware specific features from the consumers.
• The key roles of I/O subsystems are buffering, temporary IO data storage.
• OS I/O subsystems also perform caching, which store data parts for better execution, and spooling, which is interweaving on job's output with another's input.
• General device-driver interface.
• Drivers for specific hardware devices.

Protection and Security Mechanisms

• Protection includes the tools for OS defined resource access of processes.
• Security is system defense against internal and external exploits.
• User IDs (user IDs, security IDs) have names and numbers one to each user.
• User IDs then bind files, current process to access regulation to their respective users.
• Group IDs manage user packages and what every file and process within that package can do.
• Privilege escalation allows ID alterations to increase rights.

Virtualization Explained

• Permits the running of applications of a certain OS on other OSs.
• Vast and exponentially growing industry.
• Emulation uses sources that areCPU-distinct such as PowerPC running on Intel.
• VMM is a manager for (virtual machine).

Virtualization Use Cases

• Laptops and desktops are running differing OSes to explore compatibility with Apple, Mac OS X with Windows.
• Apps are able to be developed between multiple OSes without there being a need to have multiple.
• Can execute and oversee environments related to computing amid data setups.
• The VMM will launch originally where servers perform the role that the host typically world does.
• The purpose is not for hosts such as VMware ESX and the Citrix Xenserver.

Computing Environments

• The operating system provides foundations like file management, memory management, process control, and I/O.
• Programming interfaces are provided to utilize the resources.
• Virtualization supports multiple OS instances on a single physical system.

Distributed environment details

• Distributed systems involve separate and often diverse systems and networks.
• Communication occurs through TCP/IP networks like Local Area Networks (LAN), Wide Area Networks (WAN), Metropolitan Area Networks (MAN), and Personal Area Networks (PAN).
• Network OS helps to manage between systems on each network with an easy single to read layout.

Key Computer-System Architecture Concepts

• Standard processors are used.
• Distinct purpose processor are typical as well.
• Systems are growing from the importance of multiprocessors,
• Systems that are considered closely coupled like the term "parallel systems" are advantageous from Increased throughput, more economy of scale, and improved reliability through the ability to sustain faults.
• Asymmetric vs "symmetric multiprocessing", different tasks vs tasks from common pools.

Symmetric and Dual Core Multiprocessing

• Symmetric has every processor and core having shared tasks.
• Dual-core has only 2 computing cores with 1 process at a time.

Heterogenous Environments

• In Non-Uniform Memory Access, (NUMA) every processor links to only specific, different sections of given memory.

What Are Clustered Architecture

• Clusters operate much like multiprocessor designs though can have multi-machine setups.
• Storage is shared by storage area networks.
• Availability is created via a high level to make things more sustainable and fail-safe.
• Have multiple nodes running the applications and monitoring in Symmetric which is similar to multi-application hot standby.

Modern Computing Environments

• A full functioning computer includes a processor, memory, bus and I/O.
• The simplest CPUs often host various processing cores.

System Enviroments

• These include traditional, mobile/standalone, server and more dynamic forms.

General environments

• Are based on standalone machines that link to online services.
• Portals can show access internally.
• Thin clients are web terminals.
• Firewall usage and overall ubiquity.

Understand The Mobile Environment

• Can be tablets, Iphones, or the like which are all portable.
• How are smartphones different than regular computer.
• Uses GPS, gyroscope and advanced software.
• IEEE 802.11, wireless networks are main.
• Ios + Google android leaders.

Details On The Server- Client

• Terminals used to be the most popular
• Now most use servers, react to given client demands.

Computing With Peers

• Other forms of distribution systems where everyone can host servers or clients.
• Examples include Gnutella alongside Voice over IP platforms like Skype.

The Cloud

• Internet based services, compute or other forms.
• It works off functionality that is based off virtualization.
• Cloud setups use Oses, Virtual Machine Managers, tooling, firewalls, load balancing and internet to do so.

Realtime environments

• Real-time is very specific types of computers that do everything in one manner.
• Correct procedure only with restraints that are filled with multi special computers.

Open Source

• The form of OSS is made in source rather than binary for what is proprietary code. This goes against digital distribution and rights or DRM movements.
• GNU Public License, “copyleft” with different points that are champion by different groups.
• Apple and BSDUnix are two examples.
• They can use WMM and V box.

Key Kernel Data Structures

• Programming structures are common.
• Singly, doubly and circularly models exist.
• Binary search with O(1) is efficient.
• Hashmaps form in O(1) with hash functions.
• The operating system can operate and modify bits along files and sets in Linux files.