Operating systems

Learning Intentions

Understand the term operating system and how computer systems rely upon them
Understand the term GUI

Success Criteria

I can explain what an operating system does
I can provide examples of operating systems used today
I can explain the term GUI

What is an operating system?

An operating system or OS is a special piece of software that is designed to control parts of a computer system.
An operating system is one of the most important pieces of software used with a computer system.
The operating system controls the hardware, and communicates directly with the CPU, RAM, storage devices and any additional peripherals included in the computer system.

What is an operating system?

An operating system or OS is a special piece of software that is designed to control parts of a computer system.
An operating system is one of the most important pieces of software used with a computer system.
The operating system controls the hardware, and communicates directly with the CPU, RAM, storage devices and any additional peripherals included in the computer system.

The operating system provides an interface that allows users to use the computer without having to 'speak' the computer systems language.
Without an operating system, the computer is useless.
The operating system files are stored on backing storage and require a special piece of software to locate them when the computer system starts up.

The boot process

When a computer system is switched on, the boot process is started. In the boot process, the following procedures are carried out:
- The first thing a computer system does is runs a POST (Power On Self Test). This test checks that all the hardware is working correctly. If it passes the POST then it moves to the next stage.
- The next step is to check for new hardware such as more memory.
- The final step is to run a piece of software called the boot program or bootstrap loader. This contains information about where to look for the operating system. With Windows this is called Bootloader and with GNU Linux this is called GRUB.

The BIOS

The BIOS or Basic Input/Output System is a special piece of low-level software that has direct access to the computer systems hardware.
Since it gives direct access to the hardware, it is often only used by users who know what they are doing.

The BIOS

The operating system communicates directly with the BIOS, and asks the BIOS to carry out low-level operations such as moving data from one location in memory to another.
The BIOS settings are stored in the computer systems Read-Only Memory (ROM) chip.

Why do we need operating systems?

Modern operating systems

Modern operating systems are all a special class of operating systems called real time operating systems.
A real time operating system (RTOS) is one that can process data and provide feedback when the data has been processed all within a short period of time. They do not require the user to then ask the operating system what the result of the task was.
Modern operating systems also support concurrency, in other words many applications can run at the same time. Each of these applications needs to be able to use the CPU and memory from time to time.

In order to give each program a fair amount of CPU time, the operating system schedules each application using a round-robin technique.

This technique simply gives one application a few microseconds of time, then moves to the next and gives it a few microseconds of time. It keeps doing this and eventually gets back to the first application and starts the process all over again.

Modern operating systems

Modern operating systems are all a special class of operating systems called real time operating systems.
A real time operating system (RTOS) is one that can process data and provide feedback when the data has been processed all within a short period of time. They do not require the user to then ask the operating system what the result of the task was.
Modern operating systems also support concurrency, in other words many applications can run at the same time. Each of these applications needs to be able to use the CPU and memory from time to time.

In order to give each program a fair amount of CPU time, the operating system schedules each application using a round-robin technique.

This technique simply gives one application a few microseconds of time, then moves to the next and gives it a few microseconds of time. It keeps doing this and eventually gets back to the first application and starts the process all over again.

Examples of operating systems

There are many operating systems today. See how many you can name:

Windows XP

Examples of operating systems

There are many operating systems today. See how many you can name:

Windows XP

Examples of operating systems

There are many operating systems today. See how many you can name:

Windows XP

Examples of operating systems

There are many operating systems today. See how many you can name:

Mac OS X 10.6 Snow Leopard

Examples of operating systems

There are many operating systems today. See how many you can name:

Mac OS X 10.6 Snow Leopard

Examples of operating systems

There are many operating systems today. See how many you can name:

Fedora Linux

Examples of operating systems

There are many operating systems today. See how many you can name:

Fedora Linux

Examples of operating systems

There are many operating systems today. See how many you can name:

Ubuntu Linux

Examples of operating systems

There are many operating systems today. See how many you can name:

Ubuntu Linux

Examples of operating systems

There are many operating systems today. See how many you can name:

iOS 14

Examples of operating systems

There are many operating systems today. See how many you can name:

iOS 14

Examples of operating systems

There are many operating systems today. See how many you can name:

watchOS 7

Examples of operating systems

How many could you name?
Very few most likely!
There are actually so many operating systems out there today, and more being developed all the time. The most common ones are:
- Windows
- macOS / Mac OS X
- iOS
- iPad OS
- watchOS
- tvOS
- GNU/Linux (and all the flavours of it)
- BSD
- Tyzen OS

Graphical User Interfaces (GUIs)

Most modern operating systems have a graphical user interface (GUI) that allows the user to communicate with the system using a mouse or touchscreen to perform tasks.
Older operating systems used a command line interface (CLI) that allowed the user to type in commands into a command line to perform operations.

Graphical User Interfaces (GUIs)

Whilst CLI is still very common and popular today, it is often only a feature of a graphical operating system as opposed to being the only way to manage it.
CLI often gives more granular control over a computer system.

Complete the operating systems worksheet.
Research the internet for different operating systems. Create a presentation or poster identifying the purpose of the operating system, features of it, the cost of it, and whether it is open or closed source.