lecture01 - Introduction to OS_default

Introduction to Operating Systems

In this first class of Computer Science 340, led by Shamli, a professional teaching fellow, students were given an overview of the course structure and the importance of operating systems. This course will involve three lectures weekly and one optional tutorial designed to assist students with assignments. The lecture content will thoroughly cover the workings and applications of operating systems in modern computing.

Course Overview

Students are informed about the course's structure, including the assessment types which consist of three assignments (15% each), a mid-semester test (15%), and a final exam (40%). The mid-semester test, to be held on the 22nd of August, will encompass material from the first five weeks of the course. Open book assessments allow for reference materials but emphasize the need for thorough preparation despite this format.

Course Coordinators and Support

Shamli will be handling the first half of the course, while Tadiya Azu, a new lecturer, will join in week seven. Tutorials, while not mandatory, will provide essential assistance in setting students up for assignments, including an introductory session on setting up a virtual machine for practical work.

Importance of Learning Operating Systems

The lecture delves into the foundational concept of what an operating system (OS) is and its importance. An OS acts as an intermediary between computer hardware and application programs, allocating resources such as CPU time and memory. Learning about operating systems is crucial for a deeper understanding of how software interacts with hardware, allowing students to develop more efficient applications.

User vs System Perspective

From the user perspective, an operating system must be easy to use and efficient, while from the system’s point of view, it must effectively allocate resources among multiple processes. Key examples discussed include Windows, MacOS, and Linux, each representing different generations and capabilities in OS development.

Key Concepts Discussed

Multitasking and Multiprogramming

Students learned about multitasking versus multiprogramming — while multiprogramming allows multiple programs to reside in memory so that the CPU can take on another process when one is waiting for I/O, multitasking involves the OS managing running processes by allocating fixed time slices, creating the appearance of simultaneous execution.

The Role of the Kernel

The kernel is the core component of an OS, managing system resources such as process scheduling and memory. Understanding the kernel functions is essential as it operates continuously in memory and interfaces directly with both software and hardware.

Dual Mode Operation

This mechanism provides security by distinguishing between user mode (restricted access) and kernel mode (unrestricted access). When user applications perform system calls, control switches to kernel mode, allowing access to critical system resources securely.

Interrupt-Driven Operations

The OS is described as interrupt-driven, waiting for user inputs or events before processing tasks further. This model enables efficient resource management and responsiveness to user interactions.

Conclusion and Next Steps

In conclusion, the initial class served as both an introduction to the course and a foundational overview of operating systems. The following classes will elaborate on OS design and function, encouraged by readings from the recommended textbook, "Operating System Concepts (10th Edition)." Students are urged to review relevant sections to further enhance their understanding of the concepts covered.

Multitasking and Multiprogramming

Multitasking and multiprogramming are essential concepts within operating systems that address how multiple processes are handled simultaneously. Multiprogramming refers to the ability of an operating system to manage several programs residing in memory at once, which allows it to switch between them efficiently when one process is waiting for I/O operations to complete. This enhances CPU utilization by ensuring that the CPU is not idle while waiting for slower operations. On the other hand, multitasking differs in that it involves the operating system allocating fixed time slices to each running process. This time-sharing approach creates an illusion of simultaneous execution to users, as it quickly switches between processes, allowing for responsive user interactions and effective resource management. Both techniques are crucial for optimizing performance and ensuring the effective execution of running applications in a computing environment.

The Role of the Kernel

The kernel is the core component of an operating system, serving as a bridge between hardware and software. It plays a vital role in managing system resources, including the scheduling of processes and memory management. As the central part of the OS that operates continuously in memory, the kernel handles all interactions between the hardware and application programs. It ensures that each process gets the necessary resources to function while preventing conflicts between processes running concurrently. This effective resource management is essential for maintaining system stability and performance. The kernel also deals with system calls and interrupts, allowing user applications to request services from the operating system, thus facilitating smooth operation and functionality.

Dual Mode Operation

Dual mode operation is a security feature that distinguishes between user mode and kernel mode, ensuring the safe execution of processes. In user mode, applications operate with restricted access to system resources, preventing malicious or faulty programs from compromising the entire system. When a user application requires access to protected resources (like hardware), it makes a system call that triggers a switch from user mode to kernel mode, granting it the necessary privileges to execute the request. This separation is vital for protecting critical system resources from unintended access and ensuring that user applications cannot directly interfere with the OS or other processes, thus enhancing overall system security and stability.

Interrupt-Driven Operations

The interrupt-driven model is a crucial aspect of operating system design that allows efficient task management and responsiveness. In this model, the operating system remains idle, awaiting events or user inputs that trigger interrupts. These interrupts indicate that an event, such as incoming data or a user action, requires immediate attention from the OS. When an interrupt occurs, the OS pauses its current activities to address the urgent input or event, processes it, and then resumes its previous task. This approach minimizes idle CPU time and ensures that the system can respond promptly to user commands and other critical events, resulting in a more efficient and user-friendly computing environment.