1: Definition and goals of OS

Section 1: Introduction - 1: Definition and Goals of OS

An Operating System (OS) is the foundational software layer that manages a computer's hardware resources and provides essential services for application programs. It acts as an intermediary between the computer hardware and the user (or user applications), creating a usable environment from the complex underlying physical components.

Core Definition

At its heart, an OS is a resource manager and an extended machine (virtual machine):

1. Resource Manager: The OS efficiently allocates and controls the computer's fundamental resources – the Central Processing Unit (CPU), main memory (RAM), storage devices (disks, SSDs), and input/output (I/O) peripherals (keyboard, mouse, display, network). It decides which programs get access to which resources, when, and for how long, preventing conflicts and ensuring fair sharing among multiple users or applications.
2. Extended Machine / Virtual Machine: The raw hardware (CPU instructions, disk controllers, memory chips) is complex and difficult to program directly. The OS provides a simpler, more consistent, and more powerful abstraction – a virtual machine – hiding intricate hardware details. It offers high-level interfaces (like system calls and APIs) for tasks such as reading a file, displaying graphics, or allocating memory, shielding applications from low-level hardware variations.

Primary Goals

The design and operation of an OS are driven by several key, often interdependent, goals:

1. Convenience: The foremost goal is to make the computer system easy and convenient to use for both users and application developers. Without an OS, interacting with hardware would require intricate, machine-specific programming. The OS provides user interfaces (like GUIs or command lines) and standardized services (like file operations and network access), significantly simplifying interaction.
2. Efficiency: The OS must ensure the computer system operates efficiently. This involves:
   • Maximizing Resource Utilization: Ensuring the CPU, memory, I/O devices, and storage are kept busy doing useful work as much as possible, minimizing idle time.
   • Optimizing Performance: Managing resources (e.g., CPU scheduling, memory allocation, disk access) to provide good throughput (number of tasks completed per unit time) and acceptable response times for users.
3. Ability to Evolve: An OS must be designed to facilitate change and evolution over its lifetime. This means:
   • Accommodating new hardware (new processors, devices, storage technologies).
   • Supporting new applications and user requirements.
   • Allowing for the introduction of new features, services, and security updates without requiring a complete system overhaul or disrupting existing functionality. This is achieved through modular design principles and well-defined interfaces.

Fundamental Role

By fulfilling these goals, the operating system transforms a collection of electronic components into a functional, usable, and powerful computing platform. It provides the essential environment where application software can execute and users can accomplish their tasks effectively.