Software

• Software- Notes
•  Software is the programs that run on a computer.
•  System software- controls and makes use of hardware.
•  Applications software- programs which do real world tasks the user wants to do
•  Software is written by programmers using various programming languages.
•  Applications software and system software- operating system, drivers, firmware, servers, development tools, interfaces and utilities.
•  In 1937 Alan Turing thought of a device which would do any task when it was given the instructions to do it- the computer.
• The instructions are loaded into RAM from hard drive and fetched- decoded and executed by the CPU. These instructions are a 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 as a program.
• The Operating system- necessary 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
• 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 to 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 the OS and the hardware.
• The computer has peripherals in order to input output and store data. The signal that controls them is a device driver which is controlled by the software. Each peripheral has its own driver depending on the manufacturer. There 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.
• Applets- a small application that does a small task. The OS has applets built in to allow the user to e.g. change the screen resolution.
• Firmware is the initial start-up before devices 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.
• The word server applies to the hardware (the computer) and software.
• Server software responds to the requests of other programs (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.
• Servers also have their own special OS such as windows 7/8
• Any computer can be a server.
• The OS controls multi-tasking, making it look like the computer is running more than one computer 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.
• The OS controls the memory management, allocating RAM space to programs.
• 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 programs are at any one time to make efficient use of the memory and insure nothing is lost. 
• 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.
• 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 interfaces, each with their own advantages and disadvantages.
• This used to be the only way to operate a computer.
• Commands are typed in at a prompt to run programs 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.
• 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 to further menus while final options perform and action.
• Cannot edit the menu, so makes customisations.
• Graphical user interface is the way we most often control a computer.
• Programs run in windows, icons, represent files, folders and apps.
• A pointing device such as a mouse is used to control a pointer (or touch is used).
• Actions may have metaphors. Dragging a file onto the trash can means delete the file, for example
• Intuitive and easy for beginners, especially new touch interfaces for tablets and smart phones.
• This is still evolving but is becoming more widely used e.g. call centers ask the user to say numbers and or yes/no. apple iPhone has voice recognition as part of the OS-SIRI
• Windows OS currently 8.1 keeps the 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.
• On PC this is currently Yosemite. This is based on a UNIX system and has led to the iOS for mobile devices. It is a proprietary system which has enabled new ways of thinking about how a user interacts with the OS.
• This is an open source range of OS based on the UNIX kernel. UNIX works on command line but new versions of LINUX run a GUI. It is a small OS and is therefore fast and uses less memory. It is very versatile and is used on servers, and mobile devices-ANDROID