Unit 5 OS Flashcards
What is the computer Kernel
It’s a computer program at the core of the computers operating system.
It always resides in memory
It connects the application software to the hardware of the computer
What happens when a computer first starts running
It will load a bootstrap program stored in rom.
- It initializes all aspects of the system.
- knows how to load the OS
- Locates the kernel and loads it into memory
How are events signalled to the OS
Using interrupts
What does an interrupt do?
They interrupt the computer and what’s happening
How is an interrupt triggered
It’s an event triggered by a hardware signal sent to the CPU from an external device
What are the two most common interrupts
- Generated by an Input/Output Device
- Generated by a countdown timer to implement time sharing
What happens when the CPU gets an interrupt
It will save the work it was doing before the interrupt.
It will determine the type of interrupt
Handles the Interrupt
Resumes
What are the two types of interrupts
Polling - a device is ready to be read, it does not know which device is ready so it polls all of them
Vectored - OS is told which device is ready
What is a trap
It’s a software interrupt
What is an example of a trap
- Dividing by zero
- Executing invalid opcode
- Arithmetic overflow
What is multi programming
It’s the ability to run multiple programs on the same computer.
- Keeps multiple programs loaded in memory
- Os switches execution between them
- CPU never stays IDLE
What is Time Sharing
An extension of multiprogramming
What is virtual memory?
Memory that is loaded onto Non-Volatile memory. Usually it’s the non used memory moved onto a SWAP file
What are the two modes of operation (Dual-Mode Operation)
- User Mode
- Kernel Mode
What mode is the computer on at boot time
Kernel Mode
