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C191 Operating Systems for Programmers > Glossary > Flashcards

Glossary Flashcards

1
Q

Edges refer to

A

Edges refer to: the connections or relationships between entities in a resource allocation graph.

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2
Q

A back door (trapdoor)

A

A back door (trapdoor): is a mechanism that bypasses user authentication.

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3
Q

A bad block (bad sector)

A

A bad block (bad sector): is a storage block that is no longer reliable for storing and retrieving data due to physical damage.

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4
Q

A batch process

A

A batch process: performs a long-running and generally repetitive task that does not require any intervention from the user.

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5
Q

A binary semaphore

A

A binary semaphore: can take only the values 0 or 1.

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6
Q

A bitmap is a data structure where

A

A bitmap is a data structure where: each bit represents one disk block. A 1 indicates that the block is allocated and a 0 indicates that the block is free.

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7
Q

A buffer is a

A

A buffer is a: register or an area of main memory used to hold data generated by a producer process or an input device and removed from the buffer at a later time by a consumer process or an output device.

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8
Q

A buffer overflow attack

A

A buffer overflow attack: is an intrusion technique that exploits the fact that many programs do not check for array overflow, allowing an attacker to overwrite portions of memory beyond the legitimate scope of an input buffer.

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9
Q

A capability list (CL)

A

A capability list (CL): associated with a domain D contents entries of the form (O, rights), where rights specify what operations a process in domain D may apply to object O.

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10
Q

A child process

A

A child process: c of process p is a process created by p.

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11
Q

A circular buffer

A

A circular buffer: is a fixed array of buffer slots filled by the producer and emptied by the consumer one slot at a time in ascending order, modulo the buffer size.

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12
Q

A clustered block allocation scheme

A

A clustered block allocation scheme: links together sequences of contiguous blocks. The last block of any cluster points to the beginning of the logically next cluster.

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13
Q

A computer’s physical memory (RAM) is

A

A computer’s physical memory (RAM) is: a hardware structure consisting of a linear sequence of words that hold a program during execution.

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14
Q

A condition variable is

A

A condition variable is: a named queue on which processes can wait for some condition to become true.

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15
Q

A critical section is

A

A critical section is: a segment of code that cannot be entered by a process while another process is executing a corresponding segment of the code.

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16
Q

A device controller (device adapter) is

A

A device controller (device adapter) is: an electronic circuit capable of operating a specific I/O device using binary signals.

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17
Q

A device driver is a

A

A device driver is a: device-specific program that implements I/O operations, requested by user applications or the OS, by interacting with the device controller.

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18
Q

A digital signature is

A

A digital signature is: a bit string that uses public-key cryptography to undeniably link a document to the producer and guarantees that the document has not been altered in any way.

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19
Q

A directed acyclic directory hierarchy

A

A directed acyclic directory hierarchy: organizes directories such that any directory at a given level may point to zero or more files or other directories at lower levels but also permits any file or directory to have more than one parent directory.

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20
Q

A disk block cache

A

A disk block cache: is a set of main memory buffers that contain the most recently accessed disk blocks.

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21
Q

A disk block is

A

A disk block is: a fixed sequence of bytes on the disk, which can only be accessed as a single unit using low-level read-block and write-block operations.

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22
Q

A File allocation table (FAT) is

A

A File allocation table (FAT) is: an array where each entry corresponds to a disk block. The FAT keeps track of which disk blocks belong to a file by linking the blocks in a chain of indices.

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23
Q

A File control block (FCB) is a

A

A File control block (FCB) is a: data structure associated with a filename that contains all relevant attributes of the file. FCBs are stored apart from file directories and are pointed to by the corresponding directory entries.

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24
Q

A file directory (or folder) is

A

A file directory (or folder) is: a special-purpose file that records information about other files and possibly other directories.

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25
Q

A file extension is

A

A file extension is: a sequence of one or more characters following the file name.

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26
Q

A file header

A

A file header: is a portion of the file preceding the actual data and is visible to only the FS itself.

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27
Q

A file is

A

A file is: a named collection of information managed on secondary storage by the FS.

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28
Q

A file system (FS) is

A

A file system (FS) is: an integral part of every OS, whose function is to implement the concept of files.

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29
Q

A load module is

A

A load module is: a program or combination of programs in a form ready to be loaded into main memory and executed.

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30
Q

A lock

A

A lock: is a synchronization barrier through which only one process can pass at a time.

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31
Q

A logic bomb

A

A logic bomb: is unauthorized code inserted into the system and executed at a specified time to perform some destructive action.

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32
Q

A logical address is

A

A logical address is :an integer in the range [0 : m-1] that identifies a word in a logical address space.

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33
Q

A logical address space is

A

A logical address space is: an abstraction of physical memory, consisting of a sequence of imaginary memory locations in a range [0 : m-1], where m is the size of the logical address space.

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34
Q

A man-in-the-middle attack (MITM)

A

A man-in-the-middle attack (MITM): is an attack where the attacker secretly listens to, and possibly alters, the communication between two systems.

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35
Q

A message authentication code (MAC)

A

A message authentication code (MAC): is a short bit string attached to a message and used to confirm that the message came from the stated sender and has not been modified in transit.

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36
Q

A modified-bit (m-bit) is

A

A modified-bit (m-bit) is: a binary flag in each page table entry that indicates whether the corresponding page has been modified during execution.

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37
Q

A monitor is

A

A monitor is: a high-level synchronization primitive implemented using P and V operations.

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38
Q

A non-preemptive scheduling algorithm

A

A non-preemptive scheduling algorithm: allows a running process to continue until the process terminates or blocks on a resource.

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39
Q

A non-resident page refers to

A

A non-resident page refers to: a page that is not currently present in the main memory (RAM).

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40
Q

A one-time password

A

A one-time password: can be used only once and thus becomes useless when stolen.

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41
Q

A one-way hash

A

A one-way hash: function converts a variable-length input string into a fixed-length output string in a manner that cannot be inverted.

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42
Q

A page fault is

A

A page fault is: an interrupt that occurs when a program attempts to reference a non-resident page.

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43
Q

A page frame is

A

A page frame is: a fixed-size contiguous block of physical memory identified by a single number, the page frame number.

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44
Q

A page is

A

A page is: a fixed-size contiguous block of a logical address space identified by a single number, the page number.

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45
Q

A page table is

A

A page table is: an array that keeps track of which pages of a given logical address space reside in which page frames. Each page table entry corresponds to one page and contains the number or the starting address of the frame containing the page.

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46
Q

A parity bit

A

A parity bit: is a bit added to a string of bits to ensure that the total number of 1’s in the string is even or odd.

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47
Q

A period

A

A period: is a time interval (typically in milliseconds or even microseconds) within which each input item must be processed.

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48
Q

A physical address is

A

A physical address is: an integer in the range [0 : n-1] that identifies a word in a physical memory of size n.

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49
Q

A physical CPU

A

A physical CPU: is a real hardware instance of a CPU.

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50
Q

A preemptive scheduling algorithm

A

A preemptive scheduling algorithm: may stop the currently running process and choose another process to run.

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51
Q

A present bit is

A

A present bit is: a binary flag in each page table entry that indicates whether the corresponding page is currently resident in memory.

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52
Q

A priority wait

A

A priority wait: has the form c.wait(p), where c is a conditional variable and p is an integer specifying a priority according to which processes blocked on c are reactivated.

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53
Q

A privileged instruction

A

A privileged instruction: performs critical operations that access I/O devices and the CPU’s status and control registers.

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54
Q

A process creation hierarchy

A

A process creation hierarchy: is a graphical representation of the dynamically changing parent-child relationships among all processes.

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55
Q

VALUE!

A

A process is deadlocked in a state s if the process is blocked in s and if no matter what state transitions occur in the future, the process remains blocked.

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56
Q

A process p is blocked on a resource r if

A

A process p is blocked on a resource r if: one or more request edges directed from p to r exist and r does not contain sufficient free units to satisfy all requests.

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57
Q

A process

A

A process: is an instance of a program being executed by an OS.

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58
Q

A protection domain

A

A protection domain: is a set of pairs , where rights specify what operations a process may perform on the object.

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59
Q

A RAID (Redundant Array of Independent Disks)

A

A RAID (Redundant Array of Independent Disks): is a set of disks viewed by the OS as a single mass storage device.

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60
Q

A read file operation

A

A read file operation: copies data from an open file to a specified area in main memory.

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61
Q

A real-time process is

A

A real-time process is: characterized by continual input, which must be processed fast enough to generate nearly instantaneous output.

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62
Q

A record is

A

A record is: a structure of related data items, possibly of different data types, identified within a file by a record number or a unique key field.

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63
Q

A reference count is

A

A reference count is: a non-negative integer associated with a file f, which indicates how many directories are pointing to the file.

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64
Q

A reference string is

A

A reference string is: the sequence of page numbers referenced by an executing program during a given time interval.

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65
Q

A referenced bit (r-bit) is

A

A referenced bit (r-bit) is: a bit associated with a page and is set automatically by the hardware whenever the page is referenced by any instruction.

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66
Q

A relative path name is

A

A relative path name is: a concatenation of file names starting with the current directory.

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67
Q

A relocation register contains

A

A relocation register contains: the physical starting address of a program or program component in memory.

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68
Q

A resource acquisition (acq r, m)

A

A resource acquisition (acq r, m): by a process p of m units of a resource r reverses the direction of the corresponding request edges to point from the units of r to p.

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69
Q

A resource allocation graph is completely reducible if

A

A resource allocation graph is completely reducible if: at the termination of the graph reduction algorithm all processes have been deleted.

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70
Q

A resource allocation graph

A

A resource allocation graph: shows the current allocation of resources to processes and the current requests by processes for new resources.

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71
Q

A resource claim graph is

A

A resource claim graph is: an extension of the general resource allocation graph. The extended graph shows the current allocation of resources to processes andall current as well as all potential future requests by processes for new resources..

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72
Q

A resource control block (RCB)

A

A resource control block (RCB): is a data structure that represents a resource.

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73
Q

A resource is allocated to a process if

A

A resource is allocated to a process if: the process has access to and is able to utilize the resource.

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74
Q

A resource is free if

A

A resource is free if: the resource may be allocated to a requesting process.

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75
Q

A resource release

A

A resource release: (rel r, m) operation by a process p of m units of a resource r deletes m allocation edges between p and r.

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76
Q

A resource request (req r, m)

A

A resource request (req r, m): by a process p for m units of a resource r creates m new edges directed from p to r.

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77
Q

A sandbox

A

A sandbox: is a small area of memory within which a program may execute and which guarantees that the program cannot access and jump to any location outside of the designated area.

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78
Q

A schedule is feasible if

A

A schedule is feasible if: the deadlines of all processes can be met.

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79
Q

A sector

A

A sector: is a portion of a track and is the smallest unit of data that can be read or written with a single r/w operation.

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80
Q

A seek operation

A

A seek operation: moves the current position of an open file to a new specified position.

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81
Q

A segment is

A

A segment is: a variable-size block of a logical address space identified by a single number, the segment number.

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82
Q

A segment table is

A

A segment table is: an array that keeps track of which segment resides in which area of physical memory. Each entry corresponds to one segment and contains the starting address of the segment.

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83
Q

A semaphore s is

A

A semaphore s is: a non-negative integer variable that can be accessed using only two special operations, P and V.

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84
Q

A source module is

A

A source module is: a program or a program component written in a symbolic language, like C, or an assembly language, that must be translated by a compiler or assembler into executable machine code.

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85
Q

A stable read

A

A stable read: guarantees to return a valid copy of any block.

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86
Q

A stable write

A

A stable write: guarantees that every block is updated atomically.

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87
Q

A state s is a safe state if

A

A state s is a safe state if: no sequence of state transitions exists that would lead from s to a deadlock state.

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88
Q

A state s is called a deadlock state if

A

A state s is called a deadlock state if: s contains two or more deadlocked processes.

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89
Q

A supervisor call (kernel call)

A

A supervisor call (kernel call): is a privileged instruction that automatically transfers execution control to a well-defined location within the OS kernel.

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90
Q

A symbolic link (or shortcut) is a

A

A symbolic link (or shortcut) is a: directory entry that points to a file or directory just like a regular entry but is treated differently with respect to deletion. A delete operation only removes the link but not the file itself.

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91
Q

A system call

A

A system call: is a request from an application for an OS service.

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92
Q

A thread control block (TCB)

A

A thread control block (TCB): is a data structure that holds a separate copy of the dynamically changing information necessary for a thread to execute independently.

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93
Q

A thread

A

A thread: is an instance of executing a portion of a program within a process.

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94
Q

A time quantum, Q

A

A time quantum, Q: is a small amount of time (typically 10 to 100 milliseconds) during which a process is allowed to use the CPU.

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95
Q

A track

A

A track: is one of many concentric rings on a magnetic disk surface.

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96
Q

A translation lookaside buffer (TLB) is

A

A translation lookaside buffer (TLB) is: a fast associative memory buffer that maintains recent translations of logical addresses to frames in physical memory for faster retrieval.

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97
Q

A trap (also called an internal interrupt)

A

A trap (also called an internal interrupt): is an interrupt triggered by the currently executing instruction.

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98
Q

A tree-structured directory hierarchy is

A

A tree-structured directory hierarchy is: a collection of directories organized such that (1) every directory points to zero or more files or directories at the next lower level, and (2) every file and directory except the root is pointed to by exactly one parent directory at the next higher level.

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99
Q

A Trojan horse

A

A Trojan horse: is a program that appears to provide a useful service but also contains a hidden function intended to violate computer security.

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100
Q

A virus

A

A virus: is a piece of executable code that embeds itself into legitimate programs and copies itself to other programs and systems with the intention of causing harm.

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101
Q

A wait-for graph is

A

A wait-for graph is: a resource allocation graph containing only processes where each process can have multiple incoming resource allocation edges but only one outgoing resource request edge.

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102
Q

A waiting list

A

A waiting list: is associated with every resource and contains all processes blocked on that resource because the resource is not available.

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103
Q

A word is

A

A word is: a fixed-size unit of data.

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104
Q

A worm

A

A worm: is an unauthorized program, which exploits one or more systems weaknesses to spawn copies of itself on other systems via computer networks.

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105
Q

A write file operation

A

A write file operation: copies data from an area in main memory to a specified open file.

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106
Q

Abstraction

A

Abstraction: is the act of removing unimportant details or attributes of objects in order to construct more general and less complex objects.

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107
Q

access right

A

access right: The ability to execute an operation on an object.

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108
Q

advanced configuration and power interface (ACPI)

A

advanced configuration and power interface (ACPI): Firmware common to PCs and servers that manages certain aspects of hardware, including power and device information.

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109
Q

advanced technology attachment (ATA)

A

advanced technology attachment (ATA): An older-generation I/O bus.

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110
Q

An absolute path name of a file

A

An absolute path name of a file: uniquely identified by an internal ID, f, is the concatenation of the directory and file names leading from the root to the file f.

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111
Q

An access list (AL)

A

An access list (AL): associated with an object O contains entries of the form (D, rights), where rights specify what operations a process in domain D may apply to object O.

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112
Q

An access matrix

A

An access matrix: is a representation of protection domains, where each row corresponds to one domain Di, each column corresponds to one object Oi, and the intersection of the row and the column records the rights that a process in domain Di has with respect to the object Oi).

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113
Q

An access method is

A

An access method is: a set of operations provided by the OS as part of the user interface to access files.

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114
Q

An aging register is

A

An aging register is: associated with a page and is shifted periodically to the right by 1 bit. Unless the most significant bit is set to 1, the page is aging in the sense that the associated register value is steadily decreasing.

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115
Q

An error correcting code (ECC)

A

An error correcting code (ECC): includes multiple parity bits in a string to permit the detection and automatic correction of some number of erroneous bits.

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116
Q

An interactive process

A

An interactive process: communicates with the user in the form of a dialog by receiving commands or data from the keyboard or a pointing device and responding by generating output on the user’s terminal or another output device.

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117
Q

An interrupt handler

A

An interrupt handler: is a kernel function, invoked whenever an interrupt occurs, that determines the cause of the interrupt and invokes the appropriate kernel function to provide the response.

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118
Q

An interrupt

A

An interrupt: is an event that diverts the current execution of a program to a predefined location in the kernel in order to respond to an event.

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119
Q

An object module is

A

An object module is: the machine-language output of a compiler or assembler generated from a source module.

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120
Q

anonymous memory

A

anonymous memory: Memory not associated with a file. Pages not associated with a file, if dirty and paged out, must not lose their contents and are stored in swap space as anonymous memory.

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121
Q

Application program

A

Application program: A program designed for end-user execution, such as a word processor, spreadsheet, compiler, or Web browser.

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122
Q

asynchronous write

A

asynchronous write: A write that is buffered and written in arbitrary order, with the requesting thread continuing execution after the write is requested.

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123
Q

attack surface

A

attack surface: The sum of the methods available to attack a system (e.g., all of the network ports that are open, plus physical access).

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124
Q

attack

A

attack: An attempt to break a computer system’s security.

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125
Q

attacker

A

attacker: Someone attempting to breach a computer system’s security.

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126
Q

audit trail

A

audit trail: The collection of activities in a log for monitoring or review.

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127
Q

authentication

A

authentication: The process of correctly identifying a person or device. In cryptography, constraining the set of potential senders of a message.

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128
Q

back door

A

back door: A daemon left behind after a successful attack to allow continued access by the attacker. In cryptography, a method of gaining access to encrypted information without first having the secret keys. More generally, a method of passing arbitrary commands or information when an interface does not provide a standard method.

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129
Q

bad block

A

bad block: An unusable sector on an HDD.

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130
Q

basic file system

A

basic file system: A logical layer of the operating system responsible for issuing generic commands to the I/O control layer, such as “read block x,” and also buffering and caching I/O.

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131
Q

Best-fit searches

A

Best-fit searches: the entire list and chooses the smallest hole large enough to accommodate the request.

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132
Q

Biometrics

A

Biometrics: are user authentication methods that measure, record, and analyze unique physical or behavioral characteristics of a person.

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133
Q

bit-level striping

A

bit-level striping: The splitting of data at the bit level, with each bit in a byte or word stored on a separate device.

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134
Q

block-device interface

A

block-device interface: The interface for I/O to block devices.

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135
Q

block-level striping

A

block-level striping: The splitting of data at the block level, with each block stored on a separate device.

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136
Q

block

A

block: A self-contained unit of work. The smallest physical storage device storage unit, typically 512B or 4KB. In the Grand Central Dispatch Apple OS scheduler, a language extension that allows designation of a section of code that can be submitted to dispatch queues.

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137
Q

blocking

A

blocking: In interprocess communication, a mode of communication in which the sending process is blocked until the message is received by the receiving process or by a mailbox and the receiver blocks until a message is available. In I/O, a request that does not return until the I/O completes.

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138
Q

boot block

A

boot block: A block of code stored in a specific location on disk with the instructions to boot the kernel stored on that disk. The UFS boot control block.

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139
Q

boot control block

A

boot control block: A storage block of data containing information needed by the system to boot from the volume containing the block.

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140
Q

boot disk

A

boot disk: A disk that has a boot partition and a kernel to load to boot the system. A device that has a boot partition and can store an operating system for booting the computer.

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141
Q

boot partition

A

boot partition: A storage device partition containing an executable operating system.

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142
Q

boot sector

A

boot sector: The first sector of a Windows boot device, containing the bootstrap code.

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143
Q

bootstrap loader

A

bootstrap loader: The small program that loads the kernel as part of the bootstrap procedure.

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144
Q

bootstrap

A

bootstrap: The set of steps taken at computer power-on to bring the system to full operation.

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145
Q

buffer cache

A

buffer cache: In file I/O, a cache of blocks used to decrease device I/O.

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146
Q

Buffer swapping is a

A

Buffer swapping is a: technique that allows the operations of a producer process and a consumer process to overlap by using two buffers.

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147
Q

buffer

A

buffer: A memory area that stores data being transferred (e.g., between two devices or between a device and a process).

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148
Q

Busy-waiting is

A

Busy-waiting is: the act of repeatedly executing a loop while waiting for some condition to change.

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149
Q

The C-Scan scheduling algorithm

A

The C-Scan scheduling algorithm: is a variant of the Scan algorithm that services requests in only one direction. When the outermost request is reached, the r/w head sweeps back to the opposite end of the disk and starts servicing requests again in the same direction.

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150
Q

C.signal

A

C.signal: reactivates the process at the head of the queue associated with the condition variable c.

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151
Q

C.wait causes the executing process to

A

C.wait causes the executing process to: block and be placed on a waiting queue associated with the condition variable c.

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152
Q

cache

A

cache: A temporary copy of data stored in a reserved memory area to improve performance. In the slab allocator, a cache consists of two or more slabs.

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153
Q

Ceph

A

Ceph: A brand of object storage management software.

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154
Q

Challenge-response

A

Challenge-response: is a method of user authentication that has the form of a dialogue between the user and the system.

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155
Q

character-stream interface

A

character-stream interface: The interface for I/O to character devices (like keyboards).

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156
Q

cloud storage

A

cloud storage: Storage accessed from a computer over a network to a distant, shared resource data center.

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157
Q

cluster

A

cluster: In Windows storage, a power-of-2 number of disk sectors collected for I/O optimization.

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158
Q

compartmentalization

A

compartmentalization: The process of protecting each system component through the use of specific permissions and access restrictions.

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159
Q

Computer security

A

Computer security: is the freedom from theft of or damage to hardware, software, or information, and from disruption or misdirection of services.

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160
Q

Concurrency

A

Concurrency: is the act of multiple processes (or threads) executing at the same time.

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161
Q

constant angular velocity (CAV)

A

constant angular velocity (CAV): A device-recording method in which the medium spins at a constant velocity and the bit density decreases from inner to outer tracks.

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162
Q

constant linear velocity (CLV)

A

constant linear velocity (CLV): A device-recording method that keeps a constant density of bits per track by varying the rotational speed of the medium.

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163
Q

content addressable storage

A

content addressable storage: Another term for object storage; so called because objects can be retrieved based on their contents.

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164
Q

context switch

A

context switch: A context switch is the transfer of control from one process to another.

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165
Q

controller

A

controller: A special processor that manages I/O devices.

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166
Q

copy semantics

A

copy semantics: The meaning assigned to data copying—e.g., whether a block write from a process allows the data to be modified after the write has been requested.

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167
Q

copy-on-write

A

copy-on-write: Generally, the practice by which any write causes the data to first be copied and then modified, rather than overwritten. In virtual memory, on a write attempt to a shared page, the page is first copied, and the write is made to that copy.

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168
Q

Cryptography

A

Cryptography: is a technique that allows a sender to transform plaintext into a ciphertext, which the receiver can transform back to the original plaintext.

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169
Q

cylinder

A

cylinder: On an HDD, the set of tracks under the read-write heads on all platters in the device.

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170
Q

data striping

A

data striping: The splitting of data across multiple devices.

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171
Q

Decryption

A

Decryption: is the act of transforming ciphertext into the original plaintext.

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172
Q

defense in depth

A

defense in depth: The theory that more layers of defense provide stronger defense than fewer layers.

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173
Q

Demand paging is

A

Demand paging is: the principle of loading a page into memory only when the page is needed, rather than at the start of the execution.

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174
Q

denial-of-service

A

denial-of-service: Preventing legitimate use of a system.

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175
Q

device controller

A

device controller: The I/O managing processor within a device.

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176
Q

device-status table

A

device-status table: A kernel data structure for tracking the status and queues of operations for devices.

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177
Q

direct I/O

A

direct I/O: Block I/O that bypasses operating-system block features such as buffering and locking.

178
Q

Direct memory access (DMA) controller is

A

Direct memory access (DMA) controller is: a hardware component that allows devices to access main memory directly, without the involvement of the CPU.

179
Q

discretionary access control (DAC)

A

discretionary access control (DAC): Optional, as opposed to mandatory, access control.

180
Q

disk arm

A

disk arm: An HDD component that holds the read-write head and moves over cylinders of platters.

181
Q

domain switching

A

domain switching: The mechanism for switching dynamic domains.

182
Q

double buffering

A

double buffering: The copying of data twice (e.g., from a device to the kernel and then from the kernel to a process’s address space), or the use of two buffers to decouple producers and consumers.

183
Q

double caching

A

double caching: The problem in which the same data might be in two different caches; solved by a unified buffer cache.

184
Q

driver end

A

driver end: The interface between STREAMS and the device being controlled.

185
Q

dual-booted

A

dual-booted: A term describing a computer that can boot one of two or more installed operating systems.

186
Q

Dynamic relocation

A

Dynamic relocation: postpones the binding of a logical address to a physical address until the addressed item is accessed during execution.

187
Q

Edges refer to

A

Edges refer to: the connections or relationships between entities in a resource allocation graph.

188
Q

Effective access time is

A

Effective access time is: the average time to access memory in the presence of page faults.

189
Q

effective transfer rate

A

effective transfer rate: The actual, measured transfer rate of data between two devices (such as a computer and a disk drive).

190
Q

Encryption

A

Encryption: is the act of transforming plaintext into ciphertext.

191
Q

Encryption/decryption keys

A

Encryption/decryption keys: are parameters used by the encryption/decryption functions, respectively.

192
Q

eSATA

A

eSATA: A type of I/O bus.

193
Q

escape

A

escape: Generally, a method of passing arbitrary commands or information when an interface does not provide a standard method.

194
Q

extended file system

A

extended file system: The most common class of Linux file systems, with ext3 and ext4 being the most commonly used file system types.

195
Q

External memory fragmentation is

A

External memory fragmentation is: the loss of usable memory space due to holes between allocated blocks of variable sizes.

196
Q

fibre channel (FC)

A

fibre channel (FC): A type of storage I/O bus used in data centers to connect computers to storage arrays. A storage-attachment network.

197
Q

fibre channel (FC)

A

fibre channel (FC): A type of storage I/O bus used in data centers to connect computers to storage arrays. A storage-attachment network.

198
Q

file descriptor (fd)

A

file descriptor (fd): UNIX open-file pointer, created and returned to a process when it opens a file.

199
Q

file handle

A

file handle: Windows name for the open-file file descriptor.

200
Q

file system

A

file system: The system used to control data storage and retrieval; provides efficient and convenient access to storage devices by allowing data to be stored, located, and retrieved easily.

201
Q

file-control block (FCB)

A

file-control block (FCB): A per-file block that contains all the metadata about a file, such as its access permissions, access dates, and block locations.

202
Q

file-organization module

A

file-organization module: A logical layer of the operating system responsible for files and for translation of logical blocks to physical blocks.

203
Q

First-fit always starts the search from

A

First-fit always starts the search from: the beginning of the list and allocates the first hole large enough to accommodate the request.

204
Q

flash translation layer (FTL)

A

flash translation layer (FTL): For nonvolatile memory, a table that tracks currently valid blocks.

205
Q

flow control

A

flow control: Generally, a method to pause a sender of I/O. In networking, a technique to limit the rate of data flow (e.g., to avoid buffer overflow and packet loss on a router).

206
Q

free-behind

A

free-behind: Sequential I/O performance optimization that removes a page or block from a buffer as soon as I/O to the next page is requested.

207
Q

front-end processors

A

front-end processors: Small computers that perform certain tasks in an overall system; used by some systems to manage I/O and offload the general-purpose CPU.

208
Q

FTL

A

FTL: The FTL is a component used in flash memory-based storage devices (such as SSDs) to handle the translation between logical block addresses (LBAs) used by the operating system and physical addresses on the flash memory chips.

209
Q

Galois field math

A

Galois field math: An advanced error-correcting calculation done in some forms of RAID.

210
Q

garbage collection

A

garbage collection: In general, recovery of space containing no-longer-valid data.

211
Q

Guarantee mutual exclusion

A

Guarantee mutual exclusion: Only one process may be executing within the CS.

212
Q

GUIA graphical user interface (GUI)

A

GUIA graphical user interface (GUI): presets various icons on the screen, which the user can click on in different ways to invoke services associated with the icons, or to reveal pull-down menus for additional tasks.

213
Q

hacker

A

hacker: Someone attempting to breach computer security.

214
Q

Hadoop file system

A

Hadoop file system: An example of object storage management software.

215
Q

hard disk drive (HDD)

A

hard disk drive (HDD): A secondary storage device based on mechanical components, including spinning magnetic media platters and moving read-write heads.

216
Q

hardware objects

A

hardware objects: The CPU, memory devices, input/output (I/O) devices, and any other physical components that are part of a computer

217
Q

head crash

A

head crash: On an HDD, a mechanical problem involving the read-write head touching a platter.

218
Q

high-performance event timer

A

high-performance event timer: A hardware timer provided by some CPUs.

219
Q

horizontal scalability

A

horizontal scalability: The ability to scale capacity not by expanding one item but by adding more items.

220
Q

host bus adapter (HBA)

A

host bus adapter (HBA): A device controller installed in a host bus port to allow connection of one or more devices to the host.

221
Q

host controller

A

host controller: The I/O-managing processors within a computer (e.g., inside a host bus adapter).

222
Q

host-attached storage

A

host-attached storage: Storage accessed through local I/O ports (directly attached to a computer, rather than across a network or SAN).

223
Q

hot spare

A

hot spare: An unused storage device ready to be used to recover data (e.g., in a RAID set).

224
Q

hypervisor

A

hypervisor: The computer function that manages the virtual machine; also called a virtual machine manager (VMM).

225
Q

I/O bus

A

I/O bus: A physical connection of an I/O device to a computer system.

226
Q

I/O channel

A

I/O channel: A dedicated, special-purpose CPU found in large systems like mainframes for performing I/O or offloading the general-purpose CPU.

227
Q

I/O control

A

I/O control: A logical layer of the operating system responsible for controlling I/O, consisting of device drivers and interrupt handlers.

228
Q

In a contiguous block allocation scheme

A

In a contiguous block allocation scheme: every file is mapped into a contiguous sequence of disk blocks.

229
Q

InfiniBand (IB)

A

InfiniBand (IB): A high-speed network communications link.

230
Q

Information leaking

A

Information leaking: is the disclosure of confidential or secret information by a legitimate user to an unauthorized user.

231
Q

inode

A

inode: In many file systems, a per-file data structure holding most of the metadata of the file. The FCB in most UNIX file systems.

232
Q

inode

A

inode: In many file systems, a per-file data structure holding most of the metadata of the file. The FCB in most UNIX file systems.

233
Q

Internal fragmentation is

A

Internal fragmentation is: the loss of usable memory space due to the mismatch between the page size and the size of a program, which creates a hole at the end of the program’s last page.

234
Q

intruder

A

intruder: Someone attempting to breach security.

235
Q

iSCSI

A

iSCSI: The protocol used to communicate with SCSI devices; used across a network for more distant access.

236
Q

Kernel mode

A

Kernel mode: is the CPU state where both privileged and non-privileged instructions may be used.

237
Q

labels

A

labels: In mandatory access control, identifiers assigned to objects and/or subjects. The label is checked by the operating system when an operation is requested to determine if it is allowed.

238
Q

Linking is the act of

A

Linking is the act of: resolving external references among object modules and can be done statically, before loading, or dynamically, while the program is already executing.

239
Q

Load control is

A

Load control is: the activity of determining how many processes should be running concurrently at any given time to maximize overall system performance.

240
Q

logical blocks

A

logical blocks: Logical addresses used to access blocks on storage devices.

241
Q

logical file system

A

logical file system: A logical layer of the operating system responsible for file and file-system metadata management; maintains the FCBs.

242
Q

logical formatting

A

logical formatting: The creation of a file system in a volume to ready it for use.

243
Q

Login spoofing

A

Login spoofing: is an approach where a legitimate user presents a fake login screen to an unsuspecting user, who unwittingly supplies a valid login name and password to the imposter program.

244
Q

Long-term scheduling

A

Long-term scheduling: decides when a process should enter the ready state and start competing for the CPU.

245
Q

low-level formatting

A

low-level formatting: The initialization of a storage medium in preparation for its use as a computer storage device.

246
Q

magnetic tape

A

magnetic tape: A magnetic media storage device consisting of magnetic tape spooled on reels and passing over a read-write head. Used mostly for backups.

247
Q

man-in-the-middle attack

A

man-in-the-middle attack: An attack in which the attacker sits in the middle of the data flow of a communication, masquerading as the sender to the receiver and vice versa.

248
Q

mandatory access control (MAC)

A

mandatory access control (MAC): Access control settings enforced in the form of system policy.

249
Q

masquerading

A

masquerading: A practice in which a participant in a communication pretends to be someone else (another host or another person).

250
Q

master boot record (MBR)

A

master boot record (MBR): Windows boot code, stored in the first sector of a boot partition.

251
Q

master file table

A

master file table: The NTFS volume control block.

252
Q

mean time between failure (MTBF)

A

mean time between failure (MTBF): The statistical mean time that a device is expected to work correctly before failing.

253
Q

mean time to data loss

A

mean time to data loss: The statistical mean of the time until data is lost.

254
Q

mean time to repair

A

mean time to repair: The statistical mean of the time to repair a device (e.g., to get a replacement and install it).

255
Q

Memory compaction is

A

Memory compaction is: the systematic shifting of modules in memory, generally in one direction, to consolidate multiple disjoint holes into one larger hole.

256
Q

Metadata is

A

Metadata is: information about the format and organization of a file’s data and is generally stored in a file header.

257
Q

mirrored volume

A

mirrored volume: A volume in which two devices are mirrored.

258
Q

mirroring

A

mirroring: In storage, a type of RAID protection in which two physical devices contain the same content. If one device fails, the content can be read from the other.

259
Q

Moore’s law

A

Moore’s law: formulated by the scientist Gordon Moore, is the observation that the number of transistors in an integrated circuit doubles about every two years.

260
Q

mount table

A

mount table: An in-memory data structure containing information about each mounted volume. It tracks file systems and how they are accessed.

261
Q

mount table

A

mount table: An in-memory data structure containing information about each mounted volume. It tracks file systems and how they are accessed.

262
Q

mounting

A

mounting: Making a file system available for use by logically attaching it to the root file system.

263
Q

Multilevel (ML) scheduling

A

Multilevel (ML) scheduling: maintains a separate queue of processes at each priority level. Within each level, processes are scheduled using RR.

264
Q

Multiprogramming

A

Multiprogramming: is a technique that keeps several programs active in memory and switches execution among the different programs to maximize the use of the CPU and other resources.

265
Q

need-to-know principle

A

need-to-know principle: The principle that only those resources currently needed should be available to use at a given time.

266
Q

network time protocol

A

network time protocol: A network protocol for synchronizing system clocks.

267
Q

network-attached storage (NAS)

A

network-attached storage (NAS): Storage accessed from a computer over a network.

268
Q

new state

A

new state: A newly created process is placed into the new state before the process is allowed to compete for the CPU.

269
Q

Next-fit starts each search at

A

Next-fit starts each search at: the point of the last allocation.

270
Q

nonblocking

A

nonblocking: A type of I/O request that allows the initiating thread to continue while the I/O operation executes. In interprocess communication, a communication mode in which the sending process sends the message and resumes operation and the receiver process retrieves either a valid message or a null if no message is available. In I/O, a request that returns whatever data is currently available, even if it is less than requested.

271
Q

nonvolatile memory (NVM)

A

nonvolatile memory (NVM): Persistent storage based on circuits and electric charges.

272
Q

NVM express (NVMe)

A

NVM express (NVMe): A high-speed I/O bus for NVM storage.

273
Q

over-provisioning

A

over-provisioning: In non-volatile memory, space set aside for data writes that is not counted in the device free space.

274
Q

page cache

A

page cache: In file I/O, a cache that uses virtual memory techniques to cache file data as pages rather than file-system-oriented blocks for efficiency.

275
Q

Page fault rate is

A

Page fault rate is: the number of page faults, f, occurring during a number of memory references, t. The page fault rate can be expressed as P = f/t, where 0 ≤ P ≤ 1.

276
Q

Page replacement is

A

Page replacement is: the act of overwriting a page in memory with a different page loaded from the disk when needed.

277
Q

page slot

A

page slot: In Linux swap-space management, a part of the data structure tracking swap-space use.

278
Q

partition boot sector

A

partition boot sector: The NTFS boot control block.

279
Q

partition

A

partition: Logical segregation of storage space into multiple area; e.g., on HDDs, creating several groups of contiguous cylinders from the devices’ full set of cylinders.

280
Q

Peak transfer rate

A

Peak transfer rate: is the rate at which the data is streamed to or from the disk once the read/write head is at the beginning of the sector to be transferred.

281
Q

per-process open-file table

A

per-process open-file table: A kernel in-memory per-process data structure containing pointers to the system-wide open-file table, as well as other information, for all files the process has open.

282
Q

permissions

A

permissions: An entity’s access rights to an object (e.g., a user’s access rights to a file).

283
Q

phishing

A

phishing: A class of social engineering attacks in which a legitimate-looking e-mail or website tricks a user into breaching confidentiality or enabling privilege escalation.

284
Q

physical formatting

A

physical formatting: The initialization of a storage medium in preparation for its use as a computer storage device.

285
Q

platter

A

platter: An HDD component that has a magnetic media layer for holding charges.

286
Q

Polling

A

Polling: is a technique to determine whether a device is busy or idle by reading a flag set and reset by the device controller.

287
Q

pool

A

pool: In virtual memory, a group of free pages kept available for rapid allocation (e.g., for copy-on-write). In ZFS, drives, partitions, or RAID sets that can contain one or more file systems.

288
Q

positioning time

A

positioning time: On an HDD, the time it takes the read-write head to position over the desired track.

289
Q

Prevent deadlock

A

Prevent deadlock: Multiple processes trying to enter the CS at the same time must not block each other indefinitely.

290
Q

Prevent lockout

A

Prevent lockout: A process not attempting to enter the CS must not prevent other processes from entering the CS.

291
Q

Prevent starvation

A

Prevent starvation: A process (or a group of processes) must not be able to repeatedly enter the CS while other processes are waiting to enter.

292
Q

principle of least privilege

A

principle of least privilege: A design principle stating that every program and every privileged user of the system should operate using the least amount of privilege necessary to complete the job.

293
Q

privilege escalation

A

privilege escalation: The enabling of more privileges than an entity (process, system, person) should have.

294
Q

Process control block (PCB)

A

Process control block (PCB): A data structure that holds information for a process, including the current instruction address, the execution stack, the set of resources used by the process, and the program being executed.

295
Q

Program relocation is

A

Program relocation is: the act of moving a program component from one address space to another. The relocation may be between two logical address spaces or from a logical address space to a physical address space.

296
Q

programmable interval timer

A

programmable interval timer: A hardware timer provided by many CPUs.

297
Q

Programmed I/O

A

Programmed I/O: is a style of I/O programming where the CPU, running the device driver, performs the copying of all data between the I/O device controller and main memory.

298
Q

protection domain

A

protection domain: In protection, a set of resources that a process may access. In virtualization, a virtual machine manager creates a protection domain for each guest to inform the CPU of which physical memory pages belong to that guest.

299
Q

Protection

A

Protection: is the set of mechanisms and policies that guarantee computer security, including the confidentiality, integrity, availability, and authenticity of all data and services.

300
Q

Public-key cryptography (asymmetric cryptography)

A

Public-key cryptography (asymmetric cryptography): uses different keys for encryption and decryption. The encryption key is made public while the decryption key is kept private.

301
Q

RAID levels

A

RAID levels: The various types of RAID protection.

302
Q

RAM drives

A

RAM drives: Sections of a system’s DRAM presented to the rest of the system as if they were secondary storage devices.

303
Q

raw disk

A

raw disk: Direct access to a secondary storage device as an array of blocks with no file system.

304
Q

raw disk

A

raw disk: Direct access to a secondary storage device as an array of blocks with no file system.

305
Q

raw I/O

A

raw I/O: Direct access to a secondary storage device as an array of blocks with no file system.

306
Q

raw partition

A

raw partition: A partition within a storage device not containing a file system.

307
Q

read-ahead

A

read-ahead: Sequential I/O performance optimization that reads and caches several subsequent pages when a read of one page is requested.

308
Q

read-modify-write cycle

A

read-modify-write cycle: The situation in which a write of data smaller than a block requires the entire block to be read, modified, and written back.

309
Q

Ready list (RL)

A

Ready list (RL): A list containing all processes that are in the ready state and thus are able to run on the CPU.

310
Q

redundant arrays of independent disks (RAID)

A

redundant arrays of independent disks (RAID): A disk organization technique in which two or more storage devices work together, usually with protection from device failure.

311
Q

Registry

A

Registry: A file, set of files, or service used to store and retrieve configuration information. In Windows, the manager of hives of data.

312
Q

replay attack

A

replay attack: The malicious or fraudulent repetition of a valid transmission.

313
Q

replication

A

replication: In file systems, the duplication and synchronization of a set of data over a network to another system. In storage, the automatic duplication of writes between separate sites.

314
Q

Request vs Acuisition

A

Request vs Acuisition: A request is made by a process or task to the resource manager or operating system, indicating the need for a particular resource. Once a resource request is made, the system attempts to fulfill the request by allocating the requested resource to the process.

315
Q

role-based access control (RBAC)

A

role-based access control (RBAC): A method of access control in which roles rather than users have access rights; applies the principle of least privilege to the protection of operating systems.

316
Q

role

A

role: In RBAC, a named set of privileges that can be available to a user.

317
Q

root partition

A

root partition: The storage partition that contains the kernel and the root file system; the one mounted at boot.

318
Q

rotational latency

A

rotational latency: On an HDD, the time it takes the read-write head, once over the desired cylinder, to access the desired track.

319
Q

scatter-gather

A

scatter-gather: An I/O method in which multiple sources or destinations of I/O are specified in one command structure.

320
Q

Secret-key cryptography (symmetric cryptography)

A

Secret-key cryptography (symmetric cryptography): uses the same secret key for both encryption and decryption.

321
Q

Sector forwarding

A

Sector forwarding: is a technique where a bad disk block b[i] is mapped to one of the spare sectors. The mapping process involves updating the storage device’s internal logical-to-physical sector mapping table or file system structures to redirect any read or write operations targeting the original problematic block (b[i]) to the newly assigned spare sector.

322
Q

Sector slipping

A

Sector slipping: is a technique where all blocks following a bad block b[i] are shifted to the right. The last block is mapped to a spare sector and b[i] is mapped to the sector occupied previously by block b[i+1].

323
Q

sector slipping

A

sector slipping: The renaming of sectors to avoid using a bad sector.

324
Q

sector sparing

A

sector sparing: The replacement of an unusable HDD sector with another sector at some other location on the device.

325
Q

sectors

A

sectors: On an HDD platter, a fixed-size section of a track.

326
Q

secure monitor call (SMC)

A

secure monitor call (SMC): An ARM processor special instruction that can be used by the kernel to request services from the TrustZone.

327
Q

secure

A

secure: The state of a system whose resources are used and accessed as intended under all circumstances.

328
Q

seek time

A

seek time: On an HDD, the time it takes the read-write head to position over the desired cylinder.

329
Q

sense key

A

sense key: In the SCSI protocol, information in the status register indicating an error.

330
Q

serial-attached SCSI (SAS)

A

serial-attached SCSI (SAS): A common type of I/O bus.

331
Q

Service

A

Service: A software entity running on one or more machines and providing a particular type of function to calling clients. In Android, an application component with no user interface; it runs in the background while executing long-running operations or performing work for remote processes.

332
Q

session hijacking

A

session hijacking: The interception of a communication.

333
Q

Sharing is the act of

A

Sharing is the act of: linking the same copy of a module to multiple other modules.

334
Q

Short-term scheduling

A

Short-term scheduling: decides which of the ready processes should run next on the CPU.

335
Q

snapshot

A

snapshot: In file systems, a read-only view of a file system at a particular point in time; later changes do not affect the snapshot view.

336
Q

social engineering

A

social engineering: A practice in which an attacker tricks someone into performing some task for the attacker (such as sending the attacker confidential information).

337
Q

socket

A

socket: An endpoint for communication. An interface for network I/O.

338
Q

software objects

A

software objects: The software components that make up a computer or device (files, programs, semaphores, etc.).

339
Q

Solaris ZFS

A

Solaris ZFS: An advanced file system, first included as part of Solaris.

340
Q

solid-state disk

A

solid-state disk: A disk-drive-like storage device that uses flash-memory-based nonvolatile memory.

341
Q

spool

A

spool: A buffer that holds output for a device (such as a printer) that cannot accept interleaved data streams.

342
Q

SRT (Shortest Remaining Time) algorithm schedules processes according to

A

SRT (Shortest Remaining Time) algorithm schedules processes according to: the remaining CPU time needed to complete the work. The shorter the remaining CPU time, the higher the priority.

343
Q

Stable storage

A

Stable storage: is an approach to data management that uses redundancy, along with a strict protocol for reading, writing, and error recovery, to guarantee that all data remains consistent in the presence of media and crash failures.

344
Q

Starvation

A

Starvation: is the indefinite postponement of a process while other processes are allowed to proceed. Both SJF and SRT can lead to starvation.

345
Q

Static relocation

A

Static relocation: binds all logical addresses to physical addresses prior to execution.

346
Q

storage-area network (SAN)

A

storage-area network (SAN): A local-area storage network allowing multiple computers to connect to one or more storage devices.

347
Q

stream head

A

stream head: The interface between STREAMS and user processes.

348
Q

stream modules

A

stream modules: In STREAMS, modules of functionality loadable into a STREAM.

349
Q

STREAMS

A

STREAMS: A UNIX I/O feature allowing the dynamic assembly of pipelines of driver code.

350
Q

Striping

A

Striping: is a technique where a sequence of data blocks, b[i], is distributed over n disks, such that disk[i] contains block b[i] modulo n.

351
Q

Subsystem

A

Subsystem: A subset of an operating system responsible for a specific function (e.g., memory management).

352
Q

superblock

A

superblock: The UFS volume control block.

353
Q

suspended state

A

suspended state: A process may be placed into the suspended state even though the CPU and all resources are available.

354
Q

Sustained data rate

A

Sustained data rate: is the rate at which the disk can transfer data continuously.

355
Q

swap map

A

swap map: In Linux swap-space management, a part of the data structure tracking swap-space use.

356
Q

swap-space management

A

swap-space management: The low-level operating-system task of managing space on secondary storage for use in swapping and paging.

357
Q

Swapping is

A

Swapping is: the temporary removal of a module from memory. The module is saved on a disk and later moved back to memory.

358
Q

synchronous writes

A

synchronous writes: Writes that are stored in the order in which they were issued, are not buffered, and have requesting threads wait for the writes to complete before continuing.

359
Q

system disk

A

system disk: A storage device that has a boot partition and can store an operating system and other information for booting the computer.

360
Q

System service

A

System service: A collection of applications included with or added to an operating system to provide services beyond those provided by the kernel.

361
Q

System utility

A

System utility: A collection of applications included with or added to an operating system to provide services beyond what are provided by the kernel.

362
Q

system-wide open-file table

A

system-wide open-file table: A kernel in-memory data structure containing a copy of the FCB of each open file, as well as other information.

363
Q

tA shell script

A

tA shell script: is a program that implements a new operation by combining multiple commands and control statement into one named unit interpreted by the shell.

364
Q

terminal concentrator

A

terminal concentrator: A type of front-end processor for terminals.

365
Q

terminated state

A

terminated state: A process is placed into the terminated state when execution can no longer continue but before the PCB is deleted.

366
Q

The 50% rule states that

A

The 50% rule states that: if the probability of finding an exact match for a request approaches 0, one third of all memory partitions are holes and two thirds are occupied blocks. Formally, n = 0.5 m, where n is the number of holes and m is the number of occupied blocks.

367
Q

The aging page replacement algorithm

A

The aging page replacement algorithm: does not maintain pages sorted in the exact LRU order, but groups together pages referenced during a period of d consecutive references. Each period is represented by 1 bit in a periodically shifting aging register.

368
Q

The arbitration rule

A

The arbitration rule: decides which process should proceed if two or more processes have the same priority.

369
Q

The average turnaround time (ATT)

A

The average turnaround time (ATT): for a set of n processes is the mean of the n individual turnaround times.

370
Q

The close file operation

A

The close file operation: reverses the effects of the open operation by saving the current state of the file in the FCB and freeing the OFT entry.

371
Q

The CPU state

A

The CPU state: consists of all intermediate values held in any CPU registers and hardware flags at the time of the interruption.

372
Q

The CPU utilization (U) is

A

The CPU utilization (U) is: the sum of the individual fractions of CPU times used by each process.

373
Q

The create file operation causes

A

The create file operation causes: the creation of new named file.

374
Q

The create process function

A

The create process function: allocates a new PCB, fills the PCB entries with initial values, and links the PCB to other data structures in the system.

375
Q

The data transfer time

A

The data transfer time: is the time to transfer the desired number of bits to or from the disk, and is directly proportional to the disk’s rotational speed.

376
Q

The destroy file operation

A

The destroy file operation: removes an existing file from the FS.

377
Q

The destroy process function

A

The destroy process function: destroys a process by freeing the PCB data structure and removing any references to the PCB from the system.

378
Q

The earliest deadline first (EDF) algorithm schedules processes according to

A

The earliest deadline first (EDF) algorithm schedules processes according to: the shortest remaining time until the deadline. The shorter the remaining time, the higher the priority.

379
Q

The FIFO (First-In-First-Out) algorithm, also known as

A

The FIFO (First-In-First-Out) algorithm, also known as: FCFS (First-Come-First-Served), schedules processes strictly according to the process arrival time. The earlier the arrival, the higher the priority.

380
Q

The FIFO page replacement algorithm

A

The FIFO page replacement algorithm: selects the page that has been resident in memory for the longest time.

381
Q

The kernel

A

The kernel: of an OS is the minimal set of functions necessary to manage the system resources safely and efficiently.

382
Q

The least-recently-used page replacement algorithm (LRU) selects

A

The least-recently-used page replacement algorithm (LRU) selects: the page that has not been referenced for the longest time.

383
Q

The magic number is

A

The magic number is: a short sequence of characters at the start of the file header, which identifies the file type.

384
Q

The maximum claim of a process is

A

The maximum claim of a process is: the set of all resources the process may ever request.

385
Q

The open file operation

A

The open file operation: prepares a file for efficient access and manipulation by retrieving relevant file information from the FCB and storing the information in an entry of the OFT.

386
Q

The open file table (OFT) is

A

The open file table (OFT) is: a data structure that keeps track of all files currently in use to facilitate efficient access to and manipulation of the files.

387
Q

The optimal page replacement algorithm

A

The optimal page replacement algorithm: selects the page that will not be referenced for the longest time in the future.

388
Q

The optimal working set of a process is

A

The optimal working set of a process is: the set of resident pages that will still be needed in the immediate future and thus should remain resident.

389
Q

The OS shell

A

The OS shell: is a command interpreter that accepts and interprets textual commands issued by the user via a keyboard.

390
Q

The page-fault-frequency replacement algorithm

A

The page-fault-frequency replacement algorithm: takes a direct approach to controlling the page fault rate by adjusting the current resident set based on how frequently consecutive page faults occur. By adjusting the resident set based on the frequency of consecutive page faults, the page-fault-frequency algorithm aims to retain frequently accessed pages in the main memory while evicting infrequently accessed pages.

391
Q

The parent process

A

The parent process: of a process p is the process that created p.

392
Q

The principle of locality states that

A

The principle of locality states that: locations accessed recently are more likely to be accessed again than locations accessed in the distant past.

393
Q

The priority of a process (or thread)

A

The priority of a process (or thread): is a numerical value that indicates the importance of the process relative to other processes.

394
Q

The rate monotonic (RM) algorithm schedules processes according to

A

The rate monotonic (RM) algorithm schedules processes according to: the period. The shorter the period, the higher the priority.

395
Q

The release resource function

A

The release resource function: allocates the resource r to the next process on the r’s waiting list. If the waiting list is empty, r is marked as free.

396
Q

The request resource function

A

The request resource function: allocates a resource r to a process p or blocks p if r is currently allocated to another process.

397
Q

The response time of a process is

A

The response time of a process is: the elapsed time from the submission of a request (pressing the Enter key or clicking a mouse button) until the response begins to arrive.

398
Q

The root of a tree-structured directory hierarchy is

A

The root of a tree-structured directory hierarchy is: the highest level directory, which does not have a parent directory.

399
Q

The rotational delay (rotational latency)

A

The rotational delay (rotational latency): is the time to wait for the desired data item to pass under the r/w head.

400
Q

The round-robin (RR) algorithm uses

A

The round-robin (RR) algorithm uses: a single queue of processes. The priority is determined solely by a process’s position within the queue. The process at the head of the queue has the highest priority and is allowed to run for Q time units. When Q ends, the process is moved to the tail of the queue and the next process now at the head of the queue is allowed to run for Q time units.

401
Q

The Scan scheduling algorithm

A

The Scan scheduling algorithm: mimics the behavior of an elevator in a building. The r/w head maintains a current direction of travel and services all request sequentially in the current direction. When the outermost request is reached, the direction is reversed and the algorithm services all requests in the opposite direction.

402
Q

The scheduler function

A

The scheduler function: determines which process should run next and starts the process.

403
Q

The second-chance page replacement algorithm

A

The second-chance page replacement algorithm: is a coarse-grain approximation of LRU. The algorithm uses the r-bit to divide all pages into only two categories: recently referenced and not recently referenced. A page is selected from the not-recently referenced category.

404
Q

The seek time

A

The seek time: is the time to move the r/w head from the current position to the track containing the desired data.

405
Q

The Shortest seek time first (SSTF) scheduling algorithm

A

The Shortest seek time first (SSTF) scheduling algorithm: considers the list of all pending requests and always selects the request that requires the shortest travel distance from the current position.

406
Q

The SJF (Shortest Job First) algorithm, also known as

A

The SJF (Shortest Job First) algorithm, also known as: SJN (Shortest Job Next), schedules processes according to the total CPU time requirements. The shorter the required CPU time, the higher the priority.

407
Q

The test-and-set instruction (TS)

A

The test-and-set instruction (TS): copies a variable into a register and sets the variable to zero in one indivisible machine cycle.

408
Q

The third-chance page replacement algorithm, also known as

A

The third-chance page replacement algorithm, also known as: the not-recently-used page replacement algorithm (NRU), is a coarse-grain approximation of LRU, which divides pages into 4 categories based on the 4 possible combination of the r- bit and the m-bit.

409
Q

The TLB’s hit ratio is

A

The TLB’s hit ratio is: the fraction of memory accesses that find a match in the TLB.

410
Q

The turnaround time

A

The turnaround time: of a process is the time between arrival and departure, and is the sum of the total CPU time and the waiting time.

411
Q

The working set (WS) of a process at time t is

A

The working set (WS) of a process at time t is: the set of pages referenced during the past d memory operations preceding t.

412
Q

The working set page replacement algorithm

A

The working set page replacement algorithm: uses a trailing window of size d superimposed on the RS to determine the size and composition of the working set at time t.

413
Q

Thrashing is

A

Thrashing is: an execution state during which most of the time is spent on moving pages between the memory and the disk while the CPU is mostly idle and no process is making any real progress.

414
Q

threat

A

threat: The potential for a security violation.

415
Q

time sharing

A

time sharing: Multiple processes may run on one physical CPU using a technique known as time sharing.

416
Q

Time-sharing / multitasking

A

Time-sharing / multitasking: is an extension of multiprogramming where the CPU is switched periodically among all active computations to guarantee acceptable response times to each user.

417
Q

TLB

A

TLB: The TLB is a hardware cache used in processors to accelerate virtual address to physical address translation. It stores recently accessed mappings between virtual addresses and physical addresses.

418
Q

track

A

track: On an HDD platter, the medium that is under the read-write head during a rotation of the platter.

419
Q

transfer rate

A

transfer rate: The rate at which data flows.

420
Q

TrustZone (TZ)

A

TrustZone (TZ): ARM processor implementation of the most secure protection ring.

421
Q

Under the multilevel feedback (MLF) algorithm

A

Under the multilevel feedback (MLF) algorithm: a newly arriving process enters the highest-priority queue, N, and is allowed to run for Q time units. When Q is exceeded, the process is moved to the next lower priority queue, N-1, and is allowed to run for 2Q time units. The quantum size is doubled with each decreasing priority level.

422
Q

unified buffer cache

A

unified buffer cache: In file I/O, a cache used for both memory-mapped I/O and direct file I/O.

423
Q

unified virtual memory

A

unified virtual memory: In file I/O, the use of page caching for all types of I/O (explicit file system I/O and page fault I/O).

424
Q

universal serial bus (USB)

A

universal serial bus (USB): A type of I/O bus.

425
Q

UNIX file system (UFS)

A

UNIX file system (UFS): An early UNIX file systems; uses inodes for FCB.

426
Q

unstructured data

A

unstructured data: Data that are not in a fixed format (like a database record) but rather are free-form (like a twitter.com tweet).

427
Q

USB drive

A

USB drive: Nonvolatile memory in the form of a device that plugs into a USB port.

428
Q

User authentication

A

User authentication: is the act of verifying the identity of a person who wishes to connect to a computer or a network.

429
Q

User mode

A

User mode: is the CPU state where only non-privileged instructions may be used.

430
Q

utility storage

A

utility storage: An inServ feature in which storage space can be increased as needed.

431
Q

Vectored I/O

A

Vectored I/O: An I/O method in which multiple sources or destinations of I/O are specified in one command structure.

432
Q

Virtual CPU

A

Virtual CPU: A CPU that the process assumes is available only to itself.

433
Q

Virtual memory (VM) is

A

Virtual memory (VM) is: a collection of one or more logical address spaces, each of which may exceed the size of physical memory.

434
Q

virtual memory fork

A

virtual memory fork: The vfork() system call, which forks a child process, suspends the parent, and lets the child share the parent’s address space for both read and write operations (changes are visible to the parent).

435
Q

Virtualization

A

Virtualization: is the act of creating the illusion of having one or more objects with more desirable characteristics than the real object.

436
Q

volume control block

A

volume control block: A per-volume storage block containing data describing the volume.

437
Q

volume

A

volume: A container of storage; frequently, a device containing a mountable file system (including a file containing an image of the contents of a device).

438
Q

wear leveling

A

wear leveling: In nonvolatile memory, the effort to select all NAND cells over time as write targets to avoid premature media failure due to wearing out a subset of cells.

439
Q

With a linked block allocation scheme

A

With a linked block allocation scheme: the blocks containing a file may be scattered throughout the disk.

440
Q

With an indexed block allocation scheme

A

With an indexed block allocation scheme: file blocks may reside anywhere on the disk. An index table is provided for each file, which keeps track of the blocks belonging to the file.

441
Q

Worst-fit

A

Worst-fit: takes the opposite approach from best-fit by always choosing the largest available hole for any request.

C191 Operating Systems for Programmers (26 decks)

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