Monday, 17 November 2014

Event Driven Operating Systems M1

In my post I will be explaining how operating systems can be viewed as Event Driven applications. First of all I'd like to explain what Event Driven Applications really are. These applications rely on user to give them a specific input. When I say input, it could be a click, a press of a button, or even a touch on the screen (touchscreen devices). I will talk about "Windows 7" as an operating system because it is very famous and common among PC users. It is used world wide.

Start Button, Shut Down and Programs:

The start button on the modern keyboards or on the bottom left corner, when clicked, triggers an event that allows you to shutdown your keyboard with another click. You can even restart your computer or log off. Another thing it allows you to access is the Control Panel. By clicking the Start Button, you can also access various other programs by simply clicking on "All programs". This will load up a list of programs that are installed on you computer.

Keyboard text input:

Another reason why I think that Operating Systems are event driven is that it uses the keyboard. The keyboards contains buttons that are used to input specific numbers,symbols,spaces or even alphabets. There are some commands as well such as backspace or space or enter. While working with a word document, whenever we type (like I am right now) will come up on the word processor like so. This means that the user pressed a button which led up to the operating system to display that specific character on the screen for the user to see. This has to do with typing up documents.
Now, I will talk about using the keyboard for inbuilt functions. If we press Ctrl + Alt + Del it will load up the task manager. This is a useful utility. The computer depends on the user to enter these three keys simultaneously and detects the pattern. Also, I will talk about keyboard shortcuts. If we are using Google Chrome, a very common web browser, and if we want to check our history, we can press Ctrl + H to view it. This also depends on the user to trigger an event.

Keyboard commands:

On keyboards, there are specific commands that users can apply to their computer. Buttons like "F5" refreshes the desktop/page. Ctrl+Alt+Del loads up the task manager which allows you to review the functioning of your computer. The "pgup" allows you to scroll the page you are loading towards the upper section and to scroll down there is a button called "pgdn" . Often on keyboards there are three lights, these indicate "Caps Lock"  and  "Num Lock" If we press these buttons, we see the light blink on the keyboard that indicates that Num Lock is activated or Caps Lock is activated. If the light is off then it means they are deactivated. This again tells us about the event and trigger functions,
On laptop keyboards especially, there are buttons for screen brightness that allows you to control how bright or dim the screen will look. Also there are buttons to maintain the volume of the sound output. More commonly, there is a button to shut down the computer.

Mouse Click/Touch-pad touch:

One of the most common example (After keyboard buttons) that demonstrates that Operating Systems are event driven is the actual interaction between the computer and user via the mouse/touch-pad. I will be talking about the mouse, the principle of the touch pad remains the same.
The mouse is used actively throughout the user session. It is useful when you want to open files on your desktop. You have to "double click" the left mouse and your file opens up. To move the file into other folders you have to make use of the mouse by holding the left click button and dragging it onto the folder you want your file to be placed in. If you want to refresh your browser, you have to press the right click and select the option for refresh. In case of using the web, the mouse is useful when we want to highlight texts. Another reason why I feel that Operating Systems are event driven is because when we move a mouse to a hyper link, it often changes colour. It detects the interaction of the user and when the mouse is "hovered" there, it automatically changes colour. If we have previously visited that hyperlink then it's colour would already have been changed even before you hover your mouse onto it.

User Profiles:

The Operating System allows you to have multiple user profiles. When clicked on the profile, it often asks for the password. If the user manages to get the correct password then their own personal and unique desktop is loaded up where there private files are kept. The desktop can be changed in the sense that the font below icons can be changed, the background can be changed, the colour of the task bar can be changed and the user can even change the resolution. This relies on the user to trigger an event, which can be done by right click and then properties.


These are the reasons why I believe that an Operating System is purely Event Driven.

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