Lecture 4 Flashcards
What does an OS do?
The OS controls the execution of applications and acts as an interface between the apps and hardware
What are the three objectives of an OS
Convenience, evolution, efficiency
What is mutual exclusion?
OS governs the use of resources, one at a time
What are the 5 main functions of an OS
Process management, resource management, memory management, storage management, security and privacy
What is a process
A program in execution that can be assigned and executed by a processor
What are the four main problems with processes
Improper sync, failed mutual exclusion,nondeterminate program operations, deadlock
What are the three components of a process
An executable, the data, the context
First come first serve
Non preemptive, must go through each operation completely (unless I/O) uses ready queue
Shortest Job First
Makes a priority queue based on Run time, shortest to complete processes go first, non preemptive
How does CPU tell what jobs are the shortest?
By number of instructions
Shortest remaining Time next SRTN
Used to clear up RAM pre emptive
smallest Job first SJF
Preemptive used to clear space in RAM
Round Robin
Uses time slices to break up processes, preemptive algorithm, improves responsiveness
Priority based algorithm
Preemptive based on assigned priority
What are resources?
CPU, I/O BUS and memory
What is mutual exclusion
Each resource may only be used by one process at once
Who is responsible for resource management?
The OS
What are the principles of resource management
Fairness, Differential Responsiveness, Efficience
What is starvation
When a process does not get resources for a long time
What are the three methods for memory management
Paging, segmentation, and paging and Segmentation
What are the principles of storage management
Process isolation
Automatic allocation
Support for modular programming
Protection and access control
Long term storage
What are some disk search methods
CScan
Elevator algorithm
F Seek
What are the latencies involved with a hard disk
ARM time , rotational latency reading latency
What must be used for security
Hash functions (collision reistant)
