2. Without an operating system your computer would be useless!
A computer contains an Operating System on its Hard Drive. This is
loaded after the computers boot up sequence, and allows the user
to use the keyboard and mouse to be able to store data to a hard
disk drive
You can find operating systems in Personal Computers, Sat
Navigation Systems, Network Servers, Mobile Phones, Game
Consoles and even CARS!

3. • The main function of a Operating
System are:
• Processor Management
• Memory Management
• Device Management
• Storage Management
• User Interface

4. If you’re a user who has many different applications open or
maybe you might be just browsing the internet and have lots of
different tabs open.
For the computer to be able to switch between these
applications or to switch between the tabs the Operating System
has to switch between different processes thousands of times a
second.

5. RAM has a limit, however your operating system may need more
primary memory than there physically is, therefore the computer
uses virtual memory.
A good example is if a computer has 2GB of RAM as primary
memory, however it could have up to 4GB of Virtual Memory. This
works by the operating system setting aside part of its secondary
storage on a storage medium e.g. hard disk/memory stick to be
used as temporary memory store. This area is know as the
temporary memory store and is called a page file or a swap file.
The operating system will use this page file once all the available
RAM has been used up in our instance if the 2GB of RAM is used
up then the OS will start to store chunks of the memory on the
secondary storage. The chunk itself is called a page and is the
same size as sector on a hard disk. All this is done automatically by
the OS.

6. • One task the operating system has to carry out is the creating and
managing of its file system on the hard disk.
• There are many different ways this can be done, and the main of
organising a system is using a filing system called FAT. FAT(File Allocation
Table) is very useful for organising files and folders on the hard disk.
• Another filing system is NTFS which is more common in modern
computers running Windows XP, Windows Vista or Windows 7. NTFS has
more advantages over the older FAT system due to it being more
efficient and having an improved file security. But both use the same
concept.
• On every hard disk the data is stored in “Sectors”. Then Sectors are
grouped together into “Clusters”.
• A cluster is the smallest amount of storage a file can use, however if a
file is smaller than a cluster the unused space is wasted. A cluster size on
average is 4kb but can vary between 2kb to 32kb. Every cluster is
numbered so that the FAT can locate each cluster on the hard disk.

8. • A Buffer is an area of memory in which is used to store data that is in
the transition of being used and stored on a storage medium. An
example of this would be if you were moving data from a digital
camera to a printer. The data transfer speed between the devices will
differ meaning that the main memory on the computer is used as a
buffer, the speed of transfer is handled by the computer allowing data
to be kept on the main memory as a buffer. The data enters the buffer
at a significant speed allowing the camera to receive it at an
appropriate sped then leaves to the printer at an appropriate speed.
However data can not be removed at the same time as being added to
the buffer. But to speed up the transfer, a process known as double
buffering is used, this is when data is transferred from for example the
camera into the first buffer, then at the same time any data kept in the
other buffer is transferred to the printer. When buffer one is full and
buffer two is empty the process is reversed, then this allows data to be
entered to buffer two and the full buffer one can be emptied and
transferred to the printer. This effectively increases the data transfer
rate.

9. Whenever a new device is added to a computer such as a mobile
phone, a printer, a scanner or any other USB device. A small piece
of software is installed windows comes preinstalled with the
required software for the device to communicate with the
computer.
This piece of software is called a “Driver”. The Driver is used as
translation software to convert the message the hardware sends
out and makes it so the Operating System can understand the
device connected.
For example; When you want to add a MP3 to your Mobile Phone
you have you have the phones driver installed on your computer
to enable the transfer of the MP3 track to the mobile phone.

10. CLI
CLI stands for Command Line Interface and is the most basic
interface you can get!
CLI was mainly seen in the early days of computing and most
computers had simple technology inside of them, especially not
advanced enough to display colour on the screen and screen
were Black and White or Green and Black, and only a keyboard
was used it wasn’t until the GUI was created that a mouse was
introduced.
The best part about a CLI was it was quick if you knew the
commands it was quicker than a GUI. The most common CLI you
probably can think of is DOS(Disk Operating System).

12. GUI
GUI stands for Graphical User Interface, the idea of having a GUI is that it is easy to
understand and to use.
However in 1981, workers in a company in America called Xerox Parc developed a
highly visual interface that involved all the same items we use today they are:
• Windows
• Icons
• Menus
• Pointers
Or in short WIMP. As soon as WIMP came on screen GUI’s have been used, each
display was divided into areas called Windows. Any application you could see on
screen or a file that were represented by a small image are called Icons. A process
could happen by the user selecting it from a Menu. And what we used today as a
mouse we call it a Pointer.
Over the years technology has evolved and we have improved displays better
than 16 colours and 256 colours. Now we have millions of colours allowing the
GUI to become the most user friendly display in the world!