full_flashcards

Question 1

Memory management

Answer 1

OS responsibility for allocating, relocating, protecting and deallocating memory.

Question 2

Paging

Answer 2

Memory divided into fixed-size pages and frames.

Question 3

Page fault

Answer 3

Happens when a page is not in main memory and must be fetched from disk.

Question 4

MMT

Answer 4

Memory Map Table; converts virtual addresses to physical addresses.

Question 5

Thrashing

Answer 5

System constantly swaps pages instead of executing.

Question 6

Bit map

Answer 6

Tracks free/used blocks using bits.

Question 7

Linked list allocation

Answer 7

Keeps a list of memory blocks (holes/processes).

Question 8

First Fit

Answer 8

Uses first hole that is large enough.

Question 9

Next Fit

Answer 9

Continues scan from last allocation point.

Question 10

Best Fit

Answer 10

Uses smallest hole that fits.

Question 11

Worst Fit

Answer 11

Allocates from largest hole.

Question 12

Quick Fit

Answer 12

Keeps separate lists of common block sizes.

Question 13

External fragmentation

Answer 13

Wasted space between allocated blocks.

Question 14

Internal fragmentation

Answer 14

Unused space inside allocated block.

Question 15

Compaction

Answer 15

Shifts processes to remove fragmentation.

Question 16

Swapping

Answer 16

Moving processes between RAM and disk.

Question 17

Buddy system

Answer 17

Allocates blocks in powers of two.

Question 18

Buddy splitting

Answer 18

Repeatedly split blocks until size fits.

Question 19

Buddy merging

Answer 19

Only buddies of equal size can combine.

Question 20

Segmentation

Answer 20

Process split into logical chunks (code, data, stack).

Question 21

Paged virtual memory

Answer 21

Logical memory divided into pages mapped to frames.

Question 22

Advantages of paging

Answer 22

No external fragmentation, supports large processes.

Question 23

Disadvantages of paging

Answer 23

Overhead, thrashing possible.

Question 24

FIFO paging

Answer 24

Oldest page replaced first.

Question 25

LRU paging

Answer 25

Least recently used page removed.

Question 26

NFU paging

Answer 26

Page with lowest reference count removed.

Question 27

Program

Answer 27

A static file on disk.

Question 28

Process

Answer 28

Running instance of a program.

Question 29

PID

Answer 29

Unique process identifier.

Question 30

Process creation

Answer 30

OS builds PCB and loads process into memory.

Question 31

Process state

Answer 31

Current condition of process (ready, running, etc.).

Question 32

New state

Answer 32

Process is being created.

Question 33

Ready state

Answer 33

Waiting for CPU.

Question 34

Running state

Answer 34

Currently executing.

Question 35

Blocked state

Answer 35

Waiting for I/O.

Question 36

Terminated state

Answer 36

Execution complete.

Question 37

PCB

Answer 37

Process Control Block.

Question 38

PCB contents

Answer 38

Registers, program counter, memory info, files, state.

Question 39

Context switch

Answer 39

Save one PCB, load another.

Question 40

Virtual CPU

Answer 40

Each process appears to run independently.

Question 41

Pre-emptive OS

Answer 41

Can interrupt process via clock interrupt.

Question 42

Non-preemptive OS

Answer 42

Process must yield CPU voluntarily.

Question 43

Concurrency

Answer 43

Multiple processes appear to execute.

Question 44

True concurrency

Answer 44

Multiple CPUs execute at same time.

Question 45

Apparent concurrency

Answer 45

Fast switching on one CPU.

Question 46

Event-driven OS

Answer 46

Triggered by interrupts.

Question 47

Interrupt

Answer 47

Signal to OS that event occurred.

Question 48

Kernel mode

Answer 48

Full privileges.

Question 49

User mode

Answer 49

Restricted access.

Question 50

Privileged instructions

Answer 50

Allowed only in kernel mode.

Question 51

Resources

Answer 51

CPU, memory, I/O devices.

Question 52

Deadlock risk

Answer 52

Competing for resources.

Question 53

Scheduler

Answer 53

Chooses which process runs next.

Question 54

Long-term scheduler

Answer 54

Admits jobs to system.

Question 55

Medium-term scheduler

Answer 55

Manages swapping.

Question 56

Short-term scheduler

Answer 56

Dispatches CPU.

Question 57

Dispatcher

Answer 57

Hands CPU to selected process.

Question 58

Dispatch latency

Answer 58

Time to switch processes.

Question 59

CPU utilization

Answer 59

How busy the processor is.

Question 60

Throughput

Answer 60

Jobs completed per time unit.

Question 61

Turnaround time

Answer 61

Arrival to completion.

Question 62

Waiting time

Answer 62

Time spent in ready queue.

Question 63

Response time

Answer 63

Submission to first output.

Question 64

FCFS

Answer 64

Runs in arrival order, if a process arrives but another is running it waits

Question 65

RR

Answer 65

Will alternate between all current arrived processes each quantum

Question 66

Quantum

Answer 66

Max time slice in Round Robin between 1/60 and 1 second

Question 67

SPN

Answer 67

Proceess starts with the first one (a) then the shortest proceess arrived

Question 68

PSPN

Answer 68

Shortest remaining time.

Question 69

HRRN

Answer 69

Selects biggest (w+s)/s.

Question 70

MLFQ

Answer 70

Multiple priority queues.

Question 71

Feedback queue behaviour

Answer 71

CPU hogs move down priority.

Question 72

Starvation

Answer 72

Process never gets CPU.

Question 73

Fairness

Answer 73

Ensuring equal scheduling chance.

Question 74

Convoy effect

Answer 74

Short jobs wait for long ones.

Question 75

Aging

Answer 75

Increase priority to avoid starvation.

Question 76

Response time formula

Answer 76

Finish time − arrival time.

Question 77

Waiting time formula

Answer 77

Response time − service time.

Question 78

Penalty ratio formula

Answer 78

Response time / service time.

Question 79

Response ratio formula

Answer 79

Service time / response time.

Question 80

gcc

Answer 80

Compiler for C programs.

Question 81

make

Answer 81

Build automation tool.

Question 82

malloc

Answer 82

Allocates heap memory.

Question 83

free

Answer 83

Releases heap memory.

Question 84

sizeof

Answer 84

Returns size of data type.

Question 85

& operator

Answer 85

Returns variable address.

Question 86

* operator

Answer 86

Dereferences pointer.

Question 87

fork()

Answer 87

Creates a child process.

Question 88

exec()

Answer 88

Replaces process image.

Question 89

exit()

Answer 89

Terminates process.

Question 90

wait()

Answer 90

Parent waits for child.

Question 91

ls

Answer 91

List directory contents.

Question 92

pwd

Answer 92

Print working directory.

Question 93

mkdir

Answer 93

Create directory.

Question 94

rmdir

Answer 94

Delete empty directory.

Question 95

cp

Answer 95

Copy files.

Question 96

mv

Answer 96

Move/rename files.

Question 97

rm

Answer 97

Delete files.

Question 98

chmod

Answer 98

Change permissions.

Question 99

chown

Answer 99

Change file owner.

Question 100

ps

Answer 100

Show running processes.

Question 101

top

Answer 101

Live process monitor.

Question 102

kill

Answer 102

Terminate process.

Question 103

man

Answer 103

Show manual pages.

Question 104

grep

Answer 104

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