Operating System

What is the Operating System?

• The Operating System is a type of Software that runs on your computer, they coordinate all the activities that the computer's hardware performs.
• It is the first program loaded by the computer's boot program and remains permanently in the memory.
• Examples of an OS include Windows, Mac OS, Linux etc

Basic Functions of an Operating System

• Booting the computer.
• Performs basic tasks such as managing peripheral devices.
• Provides a user interface such as the GUI.
• Handles system resources such as the memory and sharing the CPU's time between various different processes.

Booting the computer

• The BIOS controls the start up sequence and configures hardware devices
• Power supply fires up, once it is producing a steady output the CPU will reset
• The CPU bumps to the starting address of the BIOS start up program
• Once the start up has started the boot is underway
• It start by running a POST (Power On Self Test)]
• Checks all parts are available for start up
• Clears the CPU register and loads the address of the first instruction in the boot program
• Control is passed to the boot program and it carries out checks on the hardware to see if a BIOS is found, it is then combined with the basic BIOS and sent to the RAM as the Boot File.
• The video card is initialised
• Peripherals such as the hard disk start spinning up if they are found
• Once a bootable drive is found, the boot sector instructions are executed in the CPU.

Performing Basic Tasks

• The OS performs basic tasks such as managing peripherals. For example nowadays devices are play and play, meaning that devices can simply be plugged in in order for them to be usable.