Download Operating Systems - Chulmleigh ICT Department

Operating Systems
Software
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Learning objectives
Understand what an operating system is and its
main functions.
Know the main operating systems used today.
Learn what an interface is and about the widely
used types of interface.
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Operating system
What is an operating system?
An operating system (or OS)
is a computer program which
controls everything the
computer does.
New computers usually come
with one installed.
You cannot use any other program (software) without an
operating system.
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Yes, but what does it do?
You probably don’t think about it, but while you’re doing the
interesting stuff, your operating system is:
handling communications between
software and hardware
allocating computer memory and
managing CPU time
organizing how data is stored on
backing storage.
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Communicating
At any one time, your computer might be:
loading and saving data and programs
communicating with peripherals such as a
mouse or a printer
displaying information on the monitor.
The operating system has to communicate with the hardware
and software and manage the tasks. This prevents the
system from trying to do things like read from and write to a
USB memory stick at the same time.
Because the operating system manages what the software
does, most pieces of software need a particular operating
system to be able to function.
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Managing computer memory
Even though you think you are only doing one thing on your
computer, like working with a spreadsheet, computer memory
must be allocated to each task the computer is doing.
Computer memory is used to:
store the
spreadsheet program
store your spreadsheet file
store a copy of the image
that is being displayed on
the monitor
run the operating system.
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Allocating CPU time
If you were printing the first page of your spreadsheet while
working on the second one, the CPU’s time would need to be
divided up between:
letting you enter more
data on the keyboard
printing sheet one
displaying what is going
on via your monitor.
The operating system helps
to manage which tasks take
priority.
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Two processors are better than one
The operating system splits CPU time into tiny slices and
allocates each task some time, so it appears as if the
computer is doing many things at once – multi-tasking.
Older computers only have one
microprocessor in their CPU, so can only
do one thing at a time.
Newer computers have dual core
processors, with two cores on the same
chip, each processor having its own cache.
This is like having two CPUs instead of one, so the system
works much faster.
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Types of operating systems
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Interfaces
An interface is the means by which a user can interact and
exchange information with the computer.
There are four main types of interface:
command line interfaces (CLI)
menu-based interfaces
graphical user interfaces (GUI)
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Command line interface
Older operating systems such as MS-DOS are often called
command line interfaces, or CLIs.
They are text based, and the user has to type in what they
want to do using commands the computer will understand.
They work very quickly, and don’t use up many system
resources such as memory or hard disk space, but they are
difficult to use unless you know the commands really well.
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Menu-based interface
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Graphical user interface
GUIs, or graphical user interfaces, are also easy to use.
They use pictures called
icons to represent files or
buttons, and the user clicks
on the button with a pointer
moved by a mouse.
Windows XP, OS/X
and Linux are all GUIs.
Many touch-Screen information
panels also use GUIs.
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Graphical user interface
This isn’t a real calculator, it’s a GUI that represents one.
Press the buttons below and see what happens.
The interface converts the clicks
into a code for us.
Clicking on icons with a mouse or
pointer is much easier than having
to type in the numbers for the
calculation in a format the computer
will understand, as would happen in
a CLI.
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Mobile phone interfaces
Mobile phones can have menu-based interfaces or GUIs:
This mobile phone is menu
driven. Applications are
selected using the phone’s
keypad.
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This phone has a GUI.
It has icons to represent
applications, which can be
selected.
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WIMP
In computing WIMP stands for:
Windows, Icons, Menus, Pointer.
Most WIMP interfaces are
also GUIs, but the use of
windows and menus make
them stand apart from more
basic forms of GUI.
Most modern operating
systems use
the WIMP interface.
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WIMP environments
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Summary
An operating system (or OS) is a computer program
which controls everything the computer does.
The operating system handles communication between
software and hardware, allocates computer memory and
CPU time, and organizes how data is stored on
backing storage.
The operating system helps to manage which operation
gets priority when multi-tasking.
There are three types of interfaces: command line
interfaces (CLI), menu-based interfaces, graphical user
interfaces (GUI).
WIMP (Windows, Icons, Menus, Pointer) interfaces are a
type of GUI.
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