1.2.1 Flashcards
Operating Systems
A collection of programs that provide an interface between the user and computer
Paging
Memory is split up into equal-sized sections known as pages
These can then be swapped between main memory and the hard disk as needed
Segmentation
Segmentation is the splitting up of memory into logical sized divisions, known as segments which vary in size
Virtual Memory
Sections of programs not being used are temporarily moved into virtual memory through paging to free up space in RAM
Interrupts
Signals generated by software or hardware to the CPU to indicate a process needs attention
Interrupt Service Routine ( ISR )
Complete current FDE cycle
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Check priority of the interrupt
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Check if it is of higher priority than the current task
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Contents of registers are stored in memory
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The relevant ISR is loaded by loading the relevant value into the PC
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When the ISR is complete , the previous state is popped from the stack
Scheduling
How the OS allocates processor time to each application as they compete for the CPU
Round Robin
Each process is given a fixed amount of time , if it hasn’t finished in that time it goes back to the back of the queue again
First Come First Served
The first process to arrive is dealt with by the CPU until it is finished
Shortest Time Remaining
The process with the smallest estimated time to completion is run next
Shortest Job First
The process with the smallest estimated running time is run next
Distributed Operating System
Controls and co-ordinates many computers , presenting them to the end user as though they were a single system
Embedded Operating System
Built to perform a small range of specific tasks and are catered towards specific devices
Multi-tasking Operating System
Enables the user to carry out tasks simultaneously
Multi-user Operating System
Allows more than one person to share a computer’s resources at the same time
