Software

Software is the programs that run on a computer
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.

Functions of the operating system
The Operating System is necessary as it is to run all computing devices

The operating system sits between your applications and the hardware of your computer.

The operating system deals with controlling all aspects of the computer.

This makes it easier to write applications.

The kernel is the lowest level of an OS and controls the hardware.

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 - multitasking

The OS controls multi- tasking, making it look like the computer is running more than one program at once.

It does this by switching between programs very quickly

The CPU is so fast there are times when the RAM can’t keep up (video buffering) so the CPU is instructed by the OS to do something in this time.

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.

User Interface – Menu Driven Interface

Often seen on devices where the input device is limited (e.g. a TV remote)

As all the options are there to be seen, it is much easier for novices.

Simple to navigate and easy to determine what to do.

Some options take you further menus while final options perform the actions.

Cannot edit the menu so you can make customisations

Voice Recognition

This is still evolving but is becoming more widely used e.g. call centres ask the user to say numbers and or yes/no. Apple iPhone has voice recognition as part of the OS - SIRI

Windows

Windows OS currently 8.1 keeps the entire GUI and all applications looking similar so that user can easily use them. They all use code that is part of Windows itself.

It has a huge range of capabilities far greater than the OS itself.

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.

Linux

This is an open source range of OS’ based on the UNIX works on command line but new versions of LINUX fun on a GUI. It is a small OS and is therefore fast and uses led memory. It is very versatile and is used on servers, and mobile devices – ANDROID.