What is Operating System?
An Operating System (OS) is system software that acts as an intermediary between computer hardware and user applications. It manages the computer resources, such as the processor, memory, storage, and input/output devices and provides a platform for running other software. Essentially, it enables users and programs to interact with the hardware easily and efficiently.
It performs core tasks like memory and file management, process and device management, and security to ensure all parts of the system work together smoothly. Examples of operating systems include Microsoft Windows, macOS, and Android.
Characteristic of Operating System
An Operating System (OS) is system software that manages computer hardware and software resources and provides services for application programs. To perform these functions effectively, an OS has several key characteristics:
Resource Management
The OS allocates and controls hardware resources like CPU time, memory, and I/O devices to prevent conflicts and optimize performance. It Dynamically allocates and manages all hardware and software resources to ensure they are used efficiently.
Process Management
The OS manages all running processes (programs in execution). It handles process creation, scheduling, executing, and terminating processes (running programs). The OS handles multitasking by switching between processes quickly.
Memory Management
The OS manages the system’s RAM (main memory). It keeps track of memory usage, allocates and deallocates memory to processes, and ensures that one process does not interfere with another.
File System Management
The OS manages all files stored on storage devices. It organizes data into files and directories, providing access controls and storage mechanisms. It supports file operations like read/write and ensures data integrity.
Device Management
The OS controls and coordinates input/output (I/O) devices like keyboards, printers, disks, etc. It uses device drivers and assigns devices to processes when needed.
Security and Protection
The OS protects system resources from unauthorized access. It uses passwords, authentication, permissions, and encryption to ensure data and resource security.
Multitasking and Multiprogramming
The OS allows multiple programs to run simultaneously by sharing CPU time.
This increases system efficiency and improves user experience.
Portability and Scalability
The OS can run on various hardware architectures and scale from small devices to large servers.
Networking Capability
Modern OSs support networking to connect, share data, and communicate with other systems using protocols, network drivers, and tools.
Operating System Evolution
Operating system evolution progressed from early batch processing systems in the 1950s to modern mobile and AI-powered OSs today, driven by hardware and user demands. Key stages include batch processing (1950s), multiprogramming (1960s), time-sharing (1960s-70s), the rise of GUIs (1980s) with personal computers, networked systems (1990s), and the dominance of mobile and cloud computing (2000s-Present).
Early Stages (1950s–1960s)
Serial Processing:
The very first computers had no OS. Programs were run one at a time using manual machine language input via switches or punch cards.
Batch Processing:
The first OS, GM-NAA I/O (1956), automated the process by grouping similar jobs into “batches” to minimize setup time.
Multiprogramming:
Developed to keep the CPU busy, this system allowed multiple programs to be loaded into memory at once, with the CPU switching between them. Allowed multiple programs to reside in memory simultaneously, improving CPU utilization.
The Era of Interactivity (1960s–1980s)
Time-Sharing:
Enabled multiple users to access the computer concurrently via terminals. A logical extension of multiprogramming, this allowed multiple users to interact with a single system simultaneously by giving each user a “time slice” of the CPU. Systems like MIT’s Compatible Time-Sharing System (CTSS, 1961) and Multics (1964–1969, developed by MIT, Bell Labs, and GE) pioneered this, allowing real-time interaction.
Unix and Personal Computers:
Unix Emergence: Developed at Bell Labs in 1969 by Ken Thompson and Dennis Ritchie, Unix was a portable, multiuser OS written in C. It introduced concepts like hierarchical file systems, pipes for inter-process communication, and a modular design. BSD (Berkeley Software Distribution) variants extended Unix for networking.
The rise of microprocessors (e.g., Intel 8086) made computers personal, driving OSes toward user-friendliness and graphical interfaces.
GUI-Based Systems:
The introduction of the Graphical User Interface (GUI) in the 1980s with systems like the Macintosh (1984) and Windows (1985) made computers much more user-friendly and accessible.
Modern and Future OSs (1990s–Present)
Networked and Open-Source Systems:
The 1990s saw the rise of networking features and the development of open-source OSs like Linux.
Open-Source Growth: Linux distributions like Ubuntu (2004) became user-friendly, powering servers and supercomputers.
Mobile and Cloud Operating Systems:
The 2000s saw the need for complex OSs on mobile devices, leading to platforms like iOS and Android. Cloud computing also advanced, and many modern systems are optimized for distributed computing.
Mobile OSes: Symbian (1990s–2000s) for early phones, but Android (2008, based on Linux) and iOS (2007) dominated. Android’s open-source nature enabled widespread adoption on smartphones and tablets.
Cloud and Virtualization: OSes integrated cloud services; Windows Azure (2010) and Linux-based AWS (2006) enabled scalable computing. Virtualization (e.g., VMware, 1999) allowed multiple OSes on one machine.
AI and IoT:
Today’s OS evolution is being shaped by artificial intelligence and the Internet of Things (IoT), leading to smarter and more interconnected devices.
AI Integration: OSes like Windows 11 and Android incorporate AI for features like predictive text, voice assistants (e.g., Siri, Cortana), and automated updates.
Types of Operating System
Operating systems can be categorized by their function, such as batch, time-sharing, real-time, distributed, and network systems. Other classifications include multi-programming, multi-tasking, and multi-processing based on how they handle multiple programs or processors. Common examples for personal and mobile use are Windows, macOS, Linux, Android, and iOS.
Types of operating systems based on function
Batch Operating System:
Processes jobs with similar requirements together without direct user interaction.
Time-Sharing Operating System:
Allows multiple users to share a single computer’s resources by executing a portion of each user’s job at a time.
Real-Time Operating System (RTOS):
A Real-Time Operating System (RTOS) is a specialized type of operating system designed to run applications that process data and respond to inputs immediately or within a guaranteed time limit. In an RTOS, the focus is not just on fast response, but on predictable and deterministic response. An RTOS ensures that critical tasks are executed on time, every time, without delay. These are designed to handle tasks with strict timing requirements, prioritizing critical operations to ensure they are completed within specific deadlines.
A Real-Time Operating System is used in systems that require immediate responses, such as industrial control systems or medical equipment, with strict timing constraints. RTOS is mostly used in systems where missing a deadline can cause failure—like medical devices, aircraft control, automotive systems, and robots.
RTOS can be categorized into:
Hard Real-Time Systems: Strict deadlines must be met (e.g., failure could lead to catastrophic outcomes, like in aircraft control systems).
Soft Real-Time Systems: Deadlines are important but some flexibility exists (e.g., video streaming where minor delays are tolerable).
Examples include FreeRTOS, VxWorks, RTLinux and QNX, commonly used in IoT devices, robotics, automotive systems, and industrial automation.
Distributed Operating System:
Manages a group of independent, networked computers and makes them appear as a single, unified system.
Network Operating System (NOS):
Runs on a server and allows it to manage data, users, security, and other network resources for client computers.
Types of operating systems based on processing
Multi-programming Operating System: Keeps several jobs in the main memory at the same time and allows the CPU to switch to another job when the current one is waiting.
Multi-tasking Operating System: Allows a single user to run multiple applications concurrently. This is an extension of multi-programming.
Multi-processing Operating System: Uses two or more CPUs to work on different tasks simultaneously.
Other important types
Mobile Operating System:
Designed for mobile devices like smartphones and tablets, with touch-screen interfaces and wireless connectivity.
Embedded Operating System:
Designed for a specific device and its functions, such as in appliances, cars, and other consumer electronics.
OS Services
OS Services are the essential functions provided by an Operating System to make the use of computers easy, efficient, and secure. These services help both users and application programs by offering commonly needed operations such as program execution, file handling, I/O management, memory control, and protection.
Operating System (OS) services are the core functionalities and utilities provided by the OS to manage hardware resources, support applications, and facilitate user interactions. These services ensure efficient, secure, and reliable operation of the computer system. They are typically implemented as system calls or APIs that programs can invoke.
Key OS Services (Key functions of an operating system)
Various services provided by the Operating System:
Process Management:
Manages running programs (processes) and allocates CPU time. Decides which programs get access to the CPU and for how long, making sure all running applications have the resources they need. It allocates CPU time and manages multitasking. Ensures multiple applications run concurrently without conflicts, as seen in modern OSes like Windows or Linux.
Memory Management:
Allocates and manages the computer’s memory (RAM) for the operating system and all running applications. Tracks and allocates system memory (RAM) to different programs. Allocates and deallocates RAM, manages virtual memory, and protects memory spaces to prevent unauthorized access.
File Management:
Organizes, stores, and retrieves files and directories on storage devices like hard drives. Organizes and controls access to data storage, including file creation, deletion, and permissions. Enables data persistence and sharing; supports features like encryption and backups.
Device Management (Input/Output (I/O) Management):
Manages all the hardware devices connected to the computer, such as printers, keyboards, and USB drives. Controls input/output devices like keyboard, mouse, printers, etc. Manages communication between the OS and hardware devices like keyboards, printers, and storage drives.
Security and Protection:
Protects the system and user data from unauthorized access and cyber threats. Enforces access controls, user authentication, and data integrity.
User Interface:
Provides interfaces for user interaction, such as graphical desktops or command lines. Provides a way for the user to interact with the computer, either through a command-line interface (CLI) or a graphical user interface (GUI).
Networking Services
Facilitates communication over networks, including internet access and data transfer. Enables connectivity; modern OSes like Android integrate Wi-Fi and Bluetooth management.
Linux vs Unix Kernel
Linux is an open-source kernel and operating system often contrasted with the proprietary Unix operating system, though the Linux kernel is technically Unix-like. Key differences include Linux’s open-source nature and portability across many hardware types, versus Unix’s historical proprietary model and use on servers and workstations. Both have similarities, like being multi-user multitasking systems with command-line interfaces and similar basic commands. While Linux is a direct descendant in spirit of Unix, it’s a distinct kernel with broader accessibility and hardware support.Â
Unix Kernel
Unix is a family of operating systems (OSes) that originated in the 1970s at AT&T Bell Labs. It introduced concepts like multitasking, multiuser support, and a hierarchical file system. Unix itself isn’t a single kernel but a specification, with various implementations.
Kernels: Proprietary or open-source variants, such as the BSD kernel (used in FreeBSD, macOS), System V (used in Solaris, AIX), or others. These kernels are monolithic or hybrid, handling core OS functions like process management and memory allocation.
Key Features: Emphasis on stability, portability, and security. Unix systems often use a command-line interface (CLI) and support standards like POSIX.
Linux Kernel
Linux is a free, open-source kernel developed by Linus Torvalds in 1991. It’s not based on any proprietary Unix code but was inspired by Unix principles, particularly from Minix (an educational Unix-like OS). The Linux kernel powers Linux distributions (distros) like Ubuntu, Fedora, and Red Hat Enterprise Linux.
Key Features: Highly modular, supporting a wide range of hardware. It’s monolithic with loadable modules, enabling customization. Linux emphasizes community-driven development, with frequent updates via the Linux Kernel Organization.
Key Differences: Linux vs Unix Kernel
| Feature | Linux Kernel | Unix Kernel |
| Origin | Developed by Linus Torvalds in 1991. | Developed by AT&T Bell Labs in the late 1960s. |
| License | Free. Open Source (GPL License) | Requires a license and can be expensive, though some versions are free |
| Availability | Free to download, modify, and distribute | Paid/Commercial for most versions |
| Source Code | Publicly available. Free and open-source | Proprietary; source code is not publicly available |
| Portability | Highly portable across devices (servers, mobiles, embedded systems). | Limited portability (hardware-specific versions) ; more limited to specific hardware |
| System Types | Used in Linux distros (Ubuntu, RHEL, Android) | Used in commercial Unix systems (AIX, HP-UX, Solaris) |
| Security | High security, with frequent community-driven updates | High security, but updates can be slow due to proprietary nature |
| Architecture Support | Supports wide range of hardware (x86, ARM, etc.) | Limited hardware support |
| Kernel Type | Monolithic Kernel | Monolithic Kernel (original), also supports Microkernel variations in some UNIX flavors |
| Community Support | Massive global community | Limited, vendor-based support |