YEAR 1 CO1 WEEK 24 OS AND INTERUPTS Flashcards
What is an operating system?
Core software controls how a computer operates.
Name some purposes of an OS.
Provides a user interface
Manage hardware/peripherals
Manage memory
Manage CPU usage/handles interrupts
Provide security
Provide utilities for system maintenance.
What are the four parts of the OS?
The Kernal.
Device Drivers.
User Interface.
System Utilities.
Describe the Kernal and its functions.
Kernal in different operating systems may be responsible for slightly different blend of tasks.
Loading/unloading applications from memory.
Memory management.
File management.
Data security.
Describe what FAT is.
File Allocation Table is like a map where files are stored on the hard disk.
Allows OS to identify free space.
OS updates when files altered.
Stores addresses or pointers to the start of files.
Stores file names, sizes, access rights.
Describe what NTFS is.
New Tech File System which supports larger hard disk and file sizes and longer file names.
What are Device Drivers?
Programs designed to work closely with particular pieces of software.
Device Drivers enable OS to control and communicate with Device.
What is User Interface?
Allows person to interact with the computer.
Describe the Graphical User Interface.
Very ‘friendly’ way for people to interact with computer.
As makes use of pictures,graphics and icons.
What are Utilities?
Tends to be programs that have a specific task to carry out.
Usually are maintenence programs that carry out basic household keeping tasks on a system.
File management services.
Encryption.
Compression.
Back ups.
Disk Checker - checks disk for errors.
What is polling?
The purpose of the CPU is to process data and follow instructions. Also must be able to respond to events as they happen.
Polling checks device if it needs to do anything which is inefficient but is simple and predictable.
What are interrupts?
More efficient way of finding out whether device needs CPU time using an interrupt.
Interrupt is a signal indicating process of device needs attention.
State the Interrupts Process.
If Interrupt level lower/ equal to current process current process continues.
If higher priority CPUs finishes current FDE cycle.
The contents of CPUs registers copied to stack in memory.
Location of appropriate interrupt service routine loaded into PC.
When ISR complete previous contents popped from stack and loaded back into registers.
Describe the Command Line Interface.
Commands are typed into computer at a prompt.
Users must know the commands and syntax.
Uses fewer resources than other interfaces.
Access to required operations open faster than using other interfaces.
Describe how a OS does data security.
Authentication one of the protective methods used by OS. Ensures user accessing a program is authorised and legitimate.
Can also schedule automatic backups so that device protected from data loss.
