Operating systems Flashcards
Operating System
“Collection of systems software that manages the computer. Usually supplied with the computer. Most common operating systems are Windows, Linux, Unix, MacOS, iOS.”
Memory Management
“The process of organising the flexible use of the computer’s main memory.”
Paging
“The organisation of memory into fixed-sized units, called pages. The immediate-access store is organised as a number of physical pages. The logical pages used by the SPU can be assigned by the memory management unit to any page in physical memory.”
Segmentation
“The splitting of a large program unto a number of smaller programs or segments. Each segment is a complete program that is executed separately. The function of the large program is achieved by running segments consecutively. Segmentation allows a large program to be executed on a computer with insufficient memory to store the whole program by carving up memory logically rather than physically.”
Virtual Memory
“Used when sufficient immediate-access store is not available. Part of a disk drive is allocated to be used as if it were main memory. This is very slow, and the software will attempt to use the immediate-access store if possible.”
Interrupt
“A signal generated by a source such as an input or output device or a systems software routine that causes a break in the execution of the current routine. Control passes to another routine in such a way that the original routine can be resumed after the interrupt.”
ISR
“Interrupt Service Routine”
“A software routine that hardware invokes in response to an interrupt. ISRs examine an interrupt and determine how to handle it.”
Scheduling
“The method by which central processor time is allocated in a multi-access system.”
RR
“Round Robin”
“A scheduling algorithm that deals with each user or tasks to be processed in turn.”
FCFS
“First Come First Serve”
“A scheduling algorithm that deals with each user or task in the order in which they arrive, this can be thought of as a queue.”
MLFQ
“Multi-Level Feedback Queue”
“A complex scheduling algorithm that deals with tasks based on a set of priorities and rules across different league tables, jobs in a certain table get promoted up or down their table based on these rules and can then end up in totally different tables if they relegated.”
SJF
“Shortest Job First”
“A scheduling algorithm that deals with each user or task based on the getting the smaller ones out of the way.”
SRT
“Shortest Remaining Time”
“A scheduling algorithm that deals with each user or task based on an calculating a estimated time remaking to complete.”
Distributed OS
“An operating system where the software is spread over a collection of independent, networked, communicating, and physically separate nodes.”
Embedded OS
“A highly specialised, often quite limited and cut down operating system design to fit inside a certain type of machine. For example computers in cards, tragic lights, cash machines, POS, elevators, drinks machines etc. In contrast to an operating system for a general-purpose computer, an embedded OS is typically quite limited, often running a single application. However, that single application is crucial to the device’s operation.”
