This includes: application software and system software.
System software - controls and makes use of hardware.
Application software - programmes which do real world tasks the user wants to do.
Software is written by programmes using various programming languages.
In 1937 Alan Turning thought of a device which would do
any task when it was given the instructions to do it.
The instructions are loaded into the RAM from the hard
drive and fetched - decoded and executed by the CPU. These instructions are program
i.e software.
The CPU only understands binary - machine code (low-level
language) long winded and difficult. So programmers use high-level languages to
set out algorithms.
The Operating System is necessary as it is to run all computing devices
Functions -
Manages hardware
It manages the hardware and software resources of the system.
In a desktop computer, these resources include such things
as the processor, memory, disk space and more.
For example, when you wish to save a document, the
application passes the document to the Operating System (OS).
The OS needs to use different instructions to save to a
hard disc compared with a solid state drive.
The OS uses special software called a device driver to
translate the specific instructions to save to that hardware.
Each different piece of hardware will have a device
driver to communicate between OS and the hardware.
Peripheral management
The computer has peripherals in order to input output and
store data. The signal which controls them is a device driver which is
controlled by the software. Each peripheral has its own driver depending on the
manufacturer. These are some generic device drivers in windows 7/8.
The application software doesn’t need to know about the
devices it just passes on requests from the user to the driver.
Interrupt signal is generated by a program which tells
the OS to stop a program using a device and make the CPU do a task for another
program with the device.
User settings
Applets - A small application that does a single task.
The OS has applets built in to allow the user to e.g. change the screen
resolution
Firmware
Firmware is the initial start up before device drivers
are loaded on. This is stored permanently on ROM chips e.g. BIOS - basic input
output system, which does the initial start-up of a computer.
Firmware also runs on simple devices such as a TV remote
or a camera.
Server
The word server applies to the hardware (the computer and
software.
Server software responds to the requests of other
programed (clients). It’s used on the internet and on smaller networks like we
have in school, e.g. when we ask to print - the server software processes the
request and delivers the data to the client.
Functions - Memory
Management
The OS controls the memory management, allocating RAM
space to programmes.
It determines how much memory each app has and what to do
if memory becomes full.
It manages virtual RAM
It tracks where data and programmes are at any one time
ti make efficient use of the memory and ensure nothing is the lost.
Security
OS must protect processes from each other and users from
each other because PCs are used by multiple users at home or on a network and
on the Internet.
It tracks who owns each file and what privileges the user
has on each file/folder.
Passwords to login allow you to protect your phone from
other users but also allow you to use networked computers on your own profile.
Functions - User
Interface
The OS provides a user interface.
This is what the user sees when they wish to use the
computer system.
There are different types of user interface, each with
their own advantages and dis advantages.
User Interface –
Command Line Interface
This is used to be the only way to operate a computer
Commands are typed in at a prompt to run programes or
perform actions.
Does not need a powerful computer.
Fast to get things done.
Not suitable for beginners as you need to know the
commands before you can operate the computer. Used by technicians because it is
quicker.
MAC OS
On PC this is Yosemite. This is based on a UNIX system
and has led to the iOS for mobile devices. It is a propriety system which has
enabled new ways of thinking about how a user interacts with OS.
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