IT 1100 : Introduction to Operating Systems


What is an OS?

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An operating system (sometimes abbreviated as “OS”) is the program that, after being initially loaded into the computer by a boot program, manages the hardware and all the other programs in a computer.

All Operating Systems are built on a Kernel which is the software of the Operating System used to speak to the hardware. It is this core package that separates Operating Systems one from another.

Kernel Interaction

From there a User Interface is added that allows users to have some control over the hardware. Without some type of Operating System the computer is useless.

The Kernel of the OS –

The user interface of the OS (UI) –

There are 3 main Operating Systems in use today:

Windows is built on an NT kernel. Mac OS X is built on the XNU kernel (a hybrid of the BSD and Mach kernels). OS’s in the Linux Family are built on the Linux kernel. Programs written based on one kernel cannot work on OS’s based on another kernel. Programs must be written specifically to work on Windows, Mac, or Linux.

What is Linux?

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This next website is for reference only. It is a wonderful website written by the makers of Linux.

*The Linux Development Project:*

History of Linux

Unix- The original open source operating system, was started by a group of employees, including Ken Thompson and Dennis Ritchie at AT&T’s Bell Laboratories in 1969.

Open Source- In those days, most software was created Open Source. Open Source means that the program code is open to the public. It doesn’t always mean free, but it always means that you can see and edit the code to your liking and redistribute the changes as your own.

GNU Public License- By the late 1970’s many companies were no longer distributing their code as open source. They were switching to binary distribution (.exe) or they were licensing it so that it could not be altered. This is called Proprietary Software. A man named Richard Stallman started the Open Source Movement in the early 1980’s and eventually created the GNU Public License. The GNU Public License grants these rights to the end user:

History of Linux

Because Unix was created as Open Source and was at the time, free, many versions came into existence. One of these was Minux.

Minux- M stands for minimized operating system. It was created by a man named Andrew S. Tanenbaum as a learning tool for his University. It was written in the late 1980’s and written specifically for the IBM computer. It was not released on an Open Source license. Although, inexpensive, it cost to purchase Minux.

Linux- Back in 1991, a Computer Science student named Linus Torvalds purchased a new computer. The fact that he didn’t like the DOS operating system that came with his new computer and the proprietary limitations of Minux got him interested in operating systems and from this he created his own operating system called Linux. In the beginning, he simply wanted more functionality for his personal computer. In the end, his purpose was to create a free operating system kernel so that others would not have the same frustrations as he did. Although not a direct descendent, Linux is a close cousin to Unix.

History of Linux

Current state of Linux

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Look at the charts on Wikipedia (Don’t read the page)

Current state of Linux


What is a distro? A Linux Distribution or (“distro” for short) is an Operating System built on the Linux kernel. Even though they are all different, they are grouped as the Linux Operating System then distributed as different “distros”.

Briefly check out this page - Distro families Notice the 3 main distribution families:

Why the command line?

CLI (Command Line Interface) or headless Operating System : Advantages and Disadvantages - requires little hard-drive space - requires very low resources to run this text-based system - can do anything the GUI interface can do if you know how - more control over what and how the OS works - only user interface option is the keyboard - learning curve to be able to use it


GUI (Graphical User Interface) Operating System : Advantages and Disadvantages - easy to use and easy to learn user interface. - has the option of mouse and keyboard user interface - typically easy to learn and easy to adapt to new interfaces - can use GUI interface and CLI interface on the same system - takes hard-drive space, processor power and RAM to run the graphical interface. - less control through the GUI system (someone has to program the buttons to work)

On public servers and mainframes a GUI based system is not required and often not desired. The graphical interface requires resources to allow it to run, but servers are not accessed by the general public and therefore only require minimal user interface allowing more resources for programs.


You can install a CLI (Command Line Interface) Operating System that will free up those resources allowing for faster processing and delivery of the server data. The Ubuntu distribution has a CLI version of their Operating System.

If you are using a GUI OS, you can still use text-mode commands in all three major OS’s: Windows, Mac OS X, and Linux. About 95% of the Linux commands we will learn work on Mac OS X (Unix based) and many work on Windows 10 as well. The concept of command line will help you no matter which OS you use at work and home.

One last link

*A linux installation has already been prepared for you. You will learn how to access it from home. You don’t need to install Linux on your own computer.*

Now, Start the Book:

Last Updated 08/21/2019