History of Unix/Linux

Operating system

An OS is a layer of software that sits between your applications and your

computer’s hardware. It manages the computer’s resources like the CPU, memory, and devices such as printers, keyboards, and screens. Without an operating system, you’d need to program directly in machine language for each piece of hardware.

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Operating systems

• Imagine two programs both trying to print at the same time. The OS steps in to manage that, ensuring only one gets access to the printer at once. It also makes sure that if a program is waiting for something—like data from the network—it doesn’t block the whole system. Instead, it pauses that task and lets others continue. This efficient management makes multitasking possible. Plus, it provides abstractions—like files instead of raw disk blocks—so developers can focus on writing useful programs without worrying about hardware details

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Operating system goals:�

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• Execute user programs and make solving user problems easier

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• Make the computer system convenient to use

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• Use the computer hardware in an efficient manner, acts like a
• resource manager

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• These goals may sometimes conflict. For instance, improving performance might reduce convenience. So operating system designers have to make careful choices to balance these needs.

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Examples: Android, macOS, Windows, Linux/GNU�

OS Advantages

• Operating System manages external and internal devices for example, printers,

scanners, and other.

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• Operating System provides interfaces and drivers for proper communication between system and hardware devices without needing to understand every technical detail..

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• Allows multiple applications to run simultaneously

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• Organizes and manages files on storage devices

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• Operating system allocates resources to various applications and ensures their efficient utilization.

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OS Disadvantages

• If an error occurred in your operating system, then there may be a chance that your data may not be recovered therefore always have a backup of your data.

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• Threats and viruses can attack our operating system at any time, making it challenging for the OS to keep the system protected from these dangers.

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• learning about new operating system can be a time-consuming

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• Operating systems consume system resources, including CPU, memory, and storage, which can affect the performance of other applications.

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Why was UNIX created?

• The Computing Context of the 1G60s

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• Computers were large, expensive, and shared

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• Operating systems were complex, proprietary, and specific to each machine.
• Each vendor had its own OS, and they weren’t compatible

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• Developers wanted more portable, efficient, and multi-user environments.

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• Existing systems were not flexible or user-friendly for developers

Why was UNIX created?

• Multics – The Ambitious Predecessor:
• (Multiplexed Information and Computing Service) was started in the mid- 1G60s by MIT, Bell Labs, and General Electric
• Aimed to create a next-generation, time-sharing operating system that would:
• Serve many users simultaneously.
• Be modular and easily expandable.

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• Ambitious goals:
• Real-time performance and reliability
• Hierarchical file system (tree-like structure).
• Dynamic linking and segmented memory management
• Written in a high-level language—very advanced for its time

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Why was UNIX created?

• Multics – The Ambitious Predecessor:
• But it failed
• Multics became overly complex and hard to manage

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• Development delays and high costs led Bell Labs to pull out in 1G6G

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• Although innovative, it was too ambitious for the hardware and software capabilities of the era.

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• Ken Thompson, who had worked on Multics, wanted to build something simpler—something that captured the good ideas, but left the bloat behind. That became Unix

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Why UNIX was created?

MULTICS

UNIX:

• The idea of a time-sharing OS.
• A hierarchical file system.
• User access control and shell- based interaction.

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Multics inspired UNIX but also showed the importance of simplicity and elegance in system design

Open-source

• Open Source means the source code of a software is made freely available, and users are allowed to view, modify, use, and redistribute it.

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• This idea is the foundation for Linux and many other modern tools. It’s not just about cost—it’s about freedom, collaboration, and transparency. Open source enables innovation by letting people around the world work together on the same software.

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Open Source

• Open Source means the source code of a software is made freely available, and users are allowed to view, modify, use, and redistribute it.

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• BSD’s Open Source Legacy:

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• In 1G77, researchers at the University of California, Berkeley released the first version of BSD, an enhanced Unix-like system based on Unix Version 6 (V6) from Bell Labs

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• BSD began as a set of add-ons and improvements to ATCT’s Unix, including
• tools like the C shell (csh), improved performance, and networking utilities.

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• It quickly evolved into a full Unix-like operating system used widely in
• academia and eventually in commercial products.

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History of UNIX

1G6G

1G73

1G75

»1G7G

1G87

1G70

1G73

1G7G

1G83

1GG1

System structure

• Hardware: Physical machine (CPU, memory, devices) — not part of the OS.

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• Kernel: Core of the OS that manages and controls hardware resources.

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• Shell: Interface that allows users to interact with the kernel.

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• User Applications: Programs run by users, relying on the shell and kernel to function.

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Shell, terminal, prompt, command line?

Shell, terminal, prompt, command line?

• So, in short:
• Shell: The program interpreting commands.

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• Terminal: The program displaying the shell's prompt and results.

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• Prompt: The text shown, waiting for commands.

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• Command line: The area where you type your commands.

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What is LINUX?

• Linux is NOT an open source operating system on its own.

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• Linux is a kernel, first released by Linus Torvalds in 1991. It’s combined with GNU software to form a complete operating systems like Ubuntu or Fedora (GNU tools—like compilers, libraries, and shells)

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• The code used to create Linux is free and available to the public to
• view, edit, and—for users with the appropriate skills—to contribute to.

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• Unix and Linux have comparable components, including the kernel,
• shell, and programs.

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Linux versus UNIX

• Unix and Linux are similar in many ways, and in fact, Linux was originally created to be similar to Unix. Both have similar tools for interfacing with the systems, programming tools, filesystem layouts, and other key components.

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• However, Unix is not free.

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• Over the years, a number of different operating systems have been created that attempted to be “unix-like” or “unix- compatible,” but Linux has been the most successful, far surpassing its predecessors in popularity.

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Linux versus UNIX

History of LINUX

• Linux was created in 1991 by Linus Torvalds, a then- student at the University of Helsinki. Torvalds built Linux as a free and open source alternative to Minix, another Unix clone that was predominantly used in academic settings.

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• At first, he wanted to call it ‘Freax’—a combination of ‘free’ and ‘freak’—but the server admin who hosted it renamed the folder to ‘Linux’ after a combination of Torvalds’ first name and the word Unix, and the name stuck.

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Why LINUX?

Free and Open Source

• No license fees. You can use, modify, and distribute it.

Secure and Stable

• Long uptimes, strong permissions model, fewer viruses.

Community-Supported

• Thousands of contributors and online resources.

Widely Used

• Powers servers, supercomputers, IoT, mobile (Android), cloud infrastructure.

Ideal for Developers

• Built-in tools, scripting, and full control over the system.

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LINUX

What are the different

Linux/GNU distributions?

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LINUX

• Over 600 Linux distributions, 300 actively developped. This diversity is a strength—it means people can tailor Linux for servers, desktops, security, privacy, education, gaming, and more. Some distros are designed for specific hardware; others for specific use cases

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