What is the role of an operating system
- manages computer hardware
- provides a platform for running applications
what does a system software contain
operating system and utility software
where is the operating system run?
on firmware
what is an interrupt?
signal for the CPU to stop what it is currently doing and do something else with a higher priority
how are interrupts generated in the hardware
generated by a hardware device. e.g. hardware failure
how are interrupts generated in software
- when an application stops
OR - the application requests services from the OS
How are interrupts handled?
- interrupt service routing holds the instructions, needed to be fetched decoded and executed to complete the commands of the interrupt.
- contents are copied to a stack in the RAM
- contents are added to the top of the stack, the contents will be saved for later retrieval when the interrupt is complete.
- the interrupt will then be executed instead of the original instructions.
examples of hardware interrupts
- power button may have been pressed
- moving the mouse
- clicking an icon to open a new program
- keyboard presses e.g. ctrl, alt, delete
examples of software interrupts
- a program is not responding
- division by zero
- two processes trying to access the same memory location
what is the job of a translator
translates a programme / code in to machine code (binary)
what is high level language
- uses english like statements
- one instruction translates into many machine code
- needs to be translated
advantages of high level language
- easier to debug
-easier to read and write - portable, can be used on any computer
disadvantages of high level language
- needs a translator
- user cannot directly manipulate the hardware
- program may be less efficient
low level language
- language that directly translates to machine code
- easily understood by a processor
- allows direct control over hardware components
advantages of low level languages
- complete control of system components
- doesn’t take a lot of storage
- can manipulate directly hardware
disadvantages of low level languages
- hard to write and understand
- machine dependent
- prone to errors
where is firmware stored
stored in the rom
what is the function of firmware
loads the operating system and helps the computer to boot
what is the steps of the startup
- firmware loads first
- firmware loads the OS
- OS loads the application software
what is application software
allows the user to perform an activity
