Operating systems

Operating systems

1. Why have an OS?

   • Each PC has a different combination of CPU, hard disk etc. Writing software to talk directly to every different piece of hardware on every different configuration of PC would be almost impossible
   • an operating system deals with multitasking, file management, security and memory usage, leaving the program to only focus on its own function
   • a program will run on any machine that can run an operating system, as a programmer, they don't need to worry what hardware the user has, or how security is handled

2. Security

   • Operating Systems have a range of security features. OS will do things like verifying a username and password, and ensuring that programs don’t damage system files

3. CPU

   • Modern processors can execute

4. Perpiherals

   • A peripheral is a device that connects to a computer, such as a printer or game controller

5. Interpreters

   • An interrupt is a method to immediately pause execution of all processes and execute a new one The OS will manage interrupt requests, backing up existing processes so they can be resumed when the interrupt is finished Interrupts can be triggered by hardware or software

6. Backing store

   • Backing stores are storage devices used to keep backups of important files Operating systems can often manage this for the user

7. Memory(RAM)

8. Multi-tasking

   • Multi-tasking is where a processor appears to be doing two tasks simultaneously
   • This is a complex task – simply alternating the instructions will result in memory being overwritten

9. Interface

   • GUI(Graphical User Interface)
     • Graphical representations of the computer’s functions are shown to the user
     • Used by most PCs and phones
     • Advantages:Easy to learn, Lots of information shown at once Disadvantages:Uses a lot of system resources, Complexity means there is more to go wrong
   • An interface is the mechanism by which the user controls the functions of the computer.
   • CLI (Command Line Interface)
     • Is a text-based interface,The user types commands, and the result is shown as text. Nearly every operating system provides a CLI.
     • Advantages:Few system resources required, Easy to automate (commands can be stored in file) Disadvantages:Hard to learn, Difficult to compare outputs of different programs