Operating Systems and System Software Flashcards
What is the purpose of a stack when handling interrupts?
Allows the processor to…
- Retrieve previous values for the original program
- Load them back into the processor registers
- Carry on executing the original program from where it left off
What happens to the values of the registers when an interrupt is received?
They are pushed onto a memory stack in a stack frame
Where are multi-user operating systems used?
In environments requiring collaboration and resource sharing among multiple users
What is the main advantage of multi-tasking systems?
Enhances user productivity and system efficiency by allowing the simultaneous execution of processes
Where are multi-tasking systems used?
Desktop environments - to run multiple applications simultaneously
Servers - to manage several user requests or services (hosting, database management, file sharing)
What is a multi-tasking operating system?
An OS which allows multiple tasks or processes to run concurrently
What is the BIOS?
A program responsible for loading the operating system when the computer first turns on
What is a boot loader?
A program used to load the OS kernel into memory
What happens once the OS has been loaded?
It takes over from ROM and boots up the rest of the system
What does the BIOS do first when turned on?
Checks all the hardware it needs is connected and working using POST (power on self test)
Clears anything that may still be in the registers of the CPU
Loads the address of the first instruction into the PC
State 5 roles of the OS
File management
Memory management
Peripheral management
Providing a user interface
Utility software
Processor scheduling
Interrupt management
Security
State the 5 scheduling algorithms
Round robin
First come first served Shortest remaining
Multi-level feedback queue
Shortest job first
Describe the round robin scheduling algorithm
Each process is given an equal time slice
If a process is not complete within the time it joins the back of the queue
Higher priority tasks can interrupt the process
Describe the first come first served scheduling algorithm
Processes are felt with in the order they come
No system of priorities
Describe the shortest remaining time scheduling algorithm
Jobs with the shortest remaining estimated time are executed until finish or until a job with a shorter remaining time interrupts the process
Describe the multi-level feedback queue scheduling algorithm
Sorts jobs into categories depending on their priority level
Describe the shortest job first scheduling algorithm
Jobs with the shortest execution time are processed first
State all the pre-emptive scheduling algorithms
Round robin
Shortest remaining time
Multi-level feedback queue
State all the non pre-emptive scheduling algorithms
First come first served Shortest job first