Week 1 – Foundations of UNIX – Written by Anthony Adams

Welcome to Fundamentals of UNIX. To understand modern computing, you have to understand UNIX. Whether you use a Mac computer, android phone, Ubuntu, Fedora, Arch or are just browsing the web (which for the most part servers run on Linux) You are interacting with the legacy system born in a lab over 50 years ago.

What is UNIX?

At the core, UNIX is an Operating System (OS).

And what broadly speaking is an OS? A compilation of multiple systems and resources that run a computer and allow users to interact with said computer. Such as:

BIOS – (firmware which is stored on the motherboard, technicality separate but is the initial boot up system, after booting up hands over control to the OS).

Kernel – Manages memory, CPU time, and hardware and is always resident in system memory.

A CLI – A command line interface allows users to interact with the machine.

A GUI – (Optional) Allows users to interact with the machine (using a graphical user interface like how you are used to, windows, macOS finder and so on).

Programs – Programs that may be bundled with the OS like a calculator, word processor, browser So on.

Unix was pioneering because it was designed from the ground up with 2 goals in mind:

Multi-user: Multiple people can have an account on 1 os and login at the same time, each running their own programs without interfering with others.

Multi-tasking: The system can handle multiple processes at the same time. This is standard today but back in 1969 it was not and computers back then could only do one thing at a time.

In Essence:

UNIX introduced the concept of Time-Sharing which allowed “slices” of the CPU’s time so fast between users and tasks, that it appeared that everyone had full resources of the computer.

Anatomy of an Operating System

As discussed above, an OS is simply a program that sits between the hardware and the user, like a resource manager that is an amalgamation of multiple programs. In UNIX we divide the system up into 3 layers:

1   The Kernel: The Heart – The hub of the OS which manages the hardware (CPU, RAM, Disks) and schedules which programs get to run.

2   The Shell:  The Interface – A program that acts as a “wrapper” around the kernel. It takes your commands and passes them to the kernel to be executed.

3   Commands/Tools: The Utility – These are

small programs like: ls, cp, grep, curl, they perform specific tasks.

A Brief History: From Bell Labs to the World

UNIX was not a corporate product at first; it was a research project.

–             1969: Born at AT&T Bell Labs. It was created by Ken Thompson, Dennis Ritchie and others after the failure of a larger project called Multics.

–             After the C revolution: Originally written in assembly, UNIX was rewritten in the C programming language in 1973. This was a massive breakthrough as it meant UNIX could be easily deployed on different hardware types.

–             1980s and 1990s: Commercial versions exploded (Solaris, AIX). In 1991, a student named Linus Torvalds created Linux, a free, unix like kernel that powers the modern internet.

NOTE: “UNIX” is a trademark owned by The Open Group. Systems like Linux and MacOS are “UNIX Like”, meaning they behave like UNIX even if they don’t carry the official branding.

The Creators and their Philosophy

UNIX was built by developers, for developers. Thus the “UNIX philosophy” which still dictates how software is written today:

1: Write programs that do one thing and do it well.

2: Write programs to work together.

3: Write programs to handle text streams, because that is a universal interface.

Because it was built for small computers (which at the time meant computers the size of a fridge, rather than the size of a whole room), it had to be efficient, modular and simple.

A Room Sized Computer:

A Fridge Sized Computer:

Why Should You Care Today?

You might be asking: “Why the heck should we be learning a 50 year old system?” The answer is: UNIX won the OS wars.

The backbone of the web: Almost every server running the web including Google, Amazon, Facebook and so on run on a UNIX-Like system (Linux).

Mobile & Desktop: Android is built on the Linux kernel. Apple’s MacOS and iOS are built on a UNIX foundation (Darwin/BSD).

The Cloud: Cloud computing is essentially

“UNIX as a Service” so if you want to work in DevOps, Cybersecurity or software engineering, UNIX is the native language for your environment.

All in all, UNIX survived and still does to this day because it was open and portable. It gave developers a consistent way to talk to hardware, regardless of who made the machine.