Operating Systems Lecture Notes PDF

Operating Systems Dr. Assem Khalaf Operating Systems  Lecture 1 3 Course Aim The Operating Systems course offers an in- depth exploration of the core principles and modern advancements in operating system design and functionality. It covers essential topics such as process management, memo...

Operating Systems Dr. Assem Khalaf Operating Systems  Lecture 1 3 Course Aim The Operating Systems course offers an in- depth exploration of the core principles and modern advancements in operating system design and functionality. It covers essential topics such as process management, memory management, file systems, and device handling. The course also delves into advanced areas like virtualization, distributed systems, real-time operating systems, and cloud-based OS architectures. 4  What is an Operating System (OS)? · An Operating System is software that acts as an intermediary between computer hardware and users. · It manages computer resources like memory, processing power, storage, and devices. Importance of an OS: · The OS makes the interaction between users and hardware easier by providing a user-friendly interface. · It ensures the smooth execution of programs by managing system resources efficiently. · Without an OS, users would need to communicate with hardware directly, which would be extremely complex. 5 Why Do Computers Need an Operating System? · An OS is essential for managing all hardware and software resources on a computer. · It acts as a bridge between the user and the computer hardware, enabling users to interact with the machine easily. 6 Managing Hardware and Software: · The OS allocates resources (like CPU time, memory space, and input/output devices) efficiently to ensure smooth operation. · It coordinates and controls the execution of software applications, allowing them to function properly. · By managing hardware and software, the OS enhances system performance and stability, ensuring that multiple applications can run simultaneously without conflicts. 7  Overview of Operating System Functions Introduction to the Five Main Functions of an Operating System: · An Operating System performs several crucial functions that are essential for the effective operation of a computer system. Memory Management: o The OS manages the computer’s memory, allocating space to programs and ensuring that they don’t interfere with each other. 8  Processor Management: o It controls the CPU, scheduling processes and managing their execution to optimize performance and responsiveness. Device Management: o The OS manages hardware devices (like printers and disks), facilitating communication between software applications and hardware components. 9  File Management: o It organizes and maintains files on storage devices, providing a structured way to store, retrieve, and manage data. Security and Access Control: o The OS ensures the security of data and system resources by implementing user permissions and protecting against unauthorized access. 10  Memory Management Overview Managing Computer Memory: RAM · Memory management is a critical function of the operating system that involves handling the computer's RAM (Random Access Memory). · The OS keeps track of each byte in memory and ensures that programs have the necessary memory space to execute. · It enables multiple applications to run simultaneously by allocating memory to them as needed and managing the available resources efficiently. 11  Allocation and Deallocation How the OS Allocates and Frees Up Memory · Allocation: o When a program needs memory, the OS allocates a specific block of RAM to it. This involves keeping track of which memory spaces are available and assigning them to different programs. · Deallocation: o Once a program finishes execution or no longer needs the memory, the OS frees up that memory, making it available for other processes. · The OS uses different algorithms (like First Fit, Best Fit, and Worst Fit) to manage memory allocation efficiently, ensuring minimal waste and optimal performance. 12  Virtual Memory Explanation of Virtual Memory and Its Role · Virtual memory is a memory management technique that creates an illusion of a large memory space, even if the actual physical memory (RAM) is limited. · It allows the OS to use disk space to extend available memory, enabling larger applications to run and multitasking without crashing. · By using virtual memory, the OS can swap data between RAM and disk storage as needed, ensuring that frequently used data is quickly accessible while less critical data can reside on slower storage. · This technique enhances system performance and provides a seamless user experience, even with memory-intensive applications. 13  Processor Management Overview Role of OS in Managing CPU Usage · Processor management is a crucial function of the operating system that involves coordinating the use of the CPU (Central Processing Unit). · The OS ensures that each process gets appropriate access to the CPU, managing the execution order and timing. · It maintains efficiency by maximizing CPU utilization, minimizing idle time, and ensuring smooth operation of multiple processes simultaneously. 14  Process Scheduling Introduction to Process Scheduling: Allocating CPU Time · Process scheduling is the method by which the OS determines which process runs at any given time on the CPU. · The OS keeps track of all processes in the system and decides their execution order based on specific criteria, like priority and required CPU time. · Effective scheduling is essential for ensuring that all processes are executed efficiently and that system resources are utilized optimally. 15  Types of Scheduling Types of Process Scheduling (Preemptive vs. Non-Preemptive) · Preemptive Scheduling: o In this type, the OS can interrupt a currently running process to allocate the CPU to another process that is ready to run. This approach helps ensure that high-priority tasks get immediate attention, improving responsiveness. · Non-Preemptive Scheduling: o Here, once a process is allocated the CPU, it runs to completion without interruption. This method is simpler and reduces overhead but can lead to longer wait times for higher-priority processes if they are queued behind long-running tasks. · The choice between preemptive and non-preemptive scheduling impacts system performance and responsiveness, depending on the workload and 16 process requirements.  Device Management Overview Managing Hardware Devices Through Device Drivers · Device management is a key function of the operating system responsible for controlling and coordinating hardware devices. · The OS uses device drivers, which are specialized software components, to communicate with and manage hardware devices. · Drivers act as translators between the OS and the hardware, ensuring that commands and data are correctly understood and processed by the device. 17  Input/Output Devices Controlling Peripheral Devices Like Keyboard, Mouse, etc. · The OS manages various input and output devices, such as keyboards, mice, printers, and scanners, enabling user interaction with the computer. · It ensures smooth data flow between the CPU and these devices, handling input signals (like keystrokes) and output signals (like display images). · Device management allows the OS to queue requests from multiple devices, prioritizing them to maintain efficient operation and responsiveness. 18  Device Communication How the OS Communicates with Hardware Devices · The OS employs different methods to communicate with hardware devices, including polling and interrupts. · Polling: The OS regularly checks the status of a device to see if it needs attention, which can be resource-intensive. · Interrupts: Devices can send signals to the OS to indicate they require processing, allowing the OS to respond immediately and efficiently. · This communication process is vital for ensuring that all hardware functions correctly and efficiently, contributing to the overall performance of the system. 19 Thank you Dr. Assem Khalaf