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
