Operating Systems

Operating Systems

1. Manages hardware and runs software

2. Main functions

   • Communicate with internal and external hardware via the device drivers
     • Use device driver software to communicate with internal hardware or peripherals connected to the computer system
     • Every piece of hardware connected to the computer system requires a device driver. Drivers essentially act as a translator for the signals between OS and hardware.
     • When a computer is booted up, the OS will choose the correct device drivers for the hardware it detects. If new hardware is connected to the computer, the system will install the new, matching driver.
     • Device manufacturers may release updates to device drivers in order to fix bugs, add features or improve the performance of their hardware. Updates may be installed automatically by the OS or manually by the user.
   • Provide a user interface, allowing a user to interact with the computer
     • User interfaces allow the user to interact with a computer system
     • GUIs are the most common type, they're easy for everyday users as they're visual, interactive, and intuitive. They have been optimised for specific input methods. They can be WIMP based (windows, icons, menus, pointers).
     • Command line interfaces are text based. The user enters specific commands to complete tasks. Command line interfaces are less resource heavy than GUIs. They're not suitable for everyday users but for advanced users, they can be far more efficient and powerful than a GUI. They can be used to automate processes using scripts.
   • Provide a platform for different applications to run
   • Allow the computer to multitask by controlling memory resources and the CPU
     • Provides a platform to run applications (by configuring hardware so they can use it, and giving access to the CPU and memory)
     • OSs that can run multiple applications at the same time are called multi tasking OSs.
     • The OS helps the CPU carry out multi tasking by efficiently managing memory and CPU processing time
     • When an application is opened, the OS moves the necessary parts of the application to memory, followed by additional parts when they are required. The OS will decide if applications or features have been used recently - if not, they may be removed from memory.
     • To run multiple applications, the OS needs to make sure that the applications do not overwrite or interfere with each other. A memory manager allocates certain applications certain memory addresses, to make sure their processes are placed into separate locations.
     • Only one application is processed by the CPU at a time, so the other processes must wait. The OS divides CPU time between open applications and may prioritise certain processes in order for instructions to be executed in the most efficient order.
     • When required, the OS organises the movement of data to and from virtual memory
     • The OS helps manage the flow of data in the system by using memory buffers. Different types of computer components, devices, and processes will send, receive, process data at different speeds - temporary memory buffers store the data until the component, device, or process is ready.
   • Deal with file management and disk management
     • Computers store data as files.
     • The OS is responsible for file management - the organisation of data is put into a usable structure
     • OS deals with naming, saving, movement, editing, deletion of data
     • OS manages the hard disk. It splits the physical disk into storage sectors, decides which sectors to write data to, and keeps track of free space on the disk. Ideally, the data for a single file would be placed in adjacent sectors.
     • OS may also include utility software to help it manage files and disks. File compression software can reduce the size of individual files and encryption software is used to secure the contents of files. Defragmentation software can help to organise and maintain the hard disk by collecting all the free space together.
     • What file management systems do
       • Enable a user to create, name, save, modify, copy, delete, and move files
       • Enable a user to search for a particular file
       • Keep track of location of files on disk or other storage device so then can be retrieved
       • Keep track of the free space on disk where files can be stored
       • Enable users to restore deleted files
       • Prevent conflicts when two users attempt to modify the same file
       • Maintain access rights to files
   • Manage the security of the system e.g. through the user accounts
     • OS can be single or multi user
     • OS is responsible for user account control. User accounts allow different users to be granted access to specific data or resources on a computer system.
     • On most desktop OSs, each user has access to their own personal data and desktop, but cannot access other users' personal data.
     • OS may have anti theft measures to prevent other users from accessing locked devices or accounts to steal information. User accounts may be password or pin protected, and some devices may need specific patterns to be drawn or fingerprint scanners.
     • Single user
       • Allow one user to use the computer at a time
       • Most common OSs are single user OSs even if the computer has multiple user accounts or is connected to the network
     • Multi user
       • Allow several users to use the computer at the same time.
       • Often used on mainframes (huge supercomputers) and give many users simultaneous access.
       • ATMs allow thousands of people access to a bank's mainframe at the same time
   • Memory management
     • Manages where in memory each program and the data it needs will go

3. Bootstrap loader

   • The computer has a piece of software known as the bootstrap loader which is a small program which loads the operating system

4. OS may have firewall utilities included but you can also buy firewall software separately