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OS FINALS REV
| Question | Answer |
|---|---|
| What is an operating system? | A program or system software that acts as an interface between the user and the computer hardware and controls the execution of all kinds of programs |
| What are the three goals of an operating system? | Execute user programs, make the computer system convenient to use, use computer hardware efficiently |
| What are the four components of a computer system? | Computer hardware, application programs, users, operating systems |
| What are the common services offered by almost all operating systems? | User interface, program execution, file system manipulation, input/output operations, communication, resource allocation, error detection, accounting, security and protection |
| What are the three types of user interface? | Command line interface, batch based interface, graphical user interface |
| What is the kernel? | The central part of an OS which manages system resources and is always resident in memory, acting as a bridge between application and hardware |
| What is a bootloader? | A program that loads and starts the boot time tasks and processes of an OS, placing the OS into memory |
| What is a batch operating system? | An operating system where jobs are processed in batches without user interaction |
| What is a time-sharing operating system? | A multitasking OS where CPU switches jobs so frequently that users can interact with each job, creating interactive computing |
| What is a distributed operating system? | A system that uses multiple central processors to serve multiple real-time applications and users, with processors communicating through communication lines |
| What is a network operating system? | An OS that runs on a server and provides the capability to manage data, users, groups, security, applications, and networking functions |
| What is a real-time operating system? | An OS intended to serve real-time systems that process data as it comes in, mostly without buffer delay |
| What is a handheld operating system? | A mobile OS built exclusively for mobile devices such as smartphones, tablets, and wearable devices |
| What is an interrupt? | A signal emitted by hardware or software when a process or event needs immediate attention, alerting the processor temporarily to a high priority process |
| What is a hardware interrupt? | A signal created and sent to the CPU caused by some action taken by a hardware device |
| What is a software interrupt? | An interrupt that arises due to illegal and erroneous use of an instruction or data, also called traps |
| What is polling in interrupt handling? | The operating system sends a signal to each device asking if they have a request |
| What is a vectored interrupt system? | The requesting device sends an interrupt to the operating system |
| What is a single-processor system? | A system with one main CPU capable of executing a general-purpose instruction set |
| What is a multiprocessor system? | A system with multiple CPUs, also known as parallel-system or multicore |
| What are the advantages of multiprocessor systems? | Increased throughput, economy of scale, increased reliability |
| What is asymmetric multiprocessing? | Each processor is assigned a specific task with a boss processor controlling the system |
| What is symmetric multiprocessing? | Each processor performs all tasks within the OS, with all processors as peers and no boss-worker relationship |
| What is a multicore system? | Multiple computing cores on a single chip, more efficient than multiple chips with single core |
| What is a clustered system? | Multiple systems working together, usually sharing storage via a storage-area network |
| What is virtualization? | A technology that allows operating systems to run as applications within other operating systems |
| What is cloud computing? | Computing that delivers computing, storage and even applications as a service across a network |
| What are the three cloud computing service models? | Software as a Service (SaaS), Platform as a Service (PaaS), Infrastructure as a Service (IaaS) |
| What is an open-source operating system? | An OS released under a license where the copyright holder allows others to study, change, and distribute the software |
| What is a process? | A program in execution |
| What are the four sections of a process in memory? | Stack, heap, text, data |
| What does the stack contain in a process? | Temporary data such as method/function parameters, return address, and local variables |
| What does the heap contain in a process? | Dynamically allocated memory during run time |
| What does the text section contain in a process? | Current activity represented by the program counter and processor registers |
| What does the data section contain in a process? | Global and static variables |
| What are the five process states? | New, running, waiting, ready, terminated |
| What is a Process Control Block? | A data block containing information associated with a specific process including process state, program counter, CPU registers, scheduling information, memory information, accounting information, I/O status |
| What is context switching? | Switching the CPU from one process to another, saving the state of the old process and loading the saved state for the new process |
| What is a parent process? | The creating process that creates new processes |
| What is a child process? | A new process created by a parent process |
| What is cascading termination? | When a process terminates, all its children must also be terminated by the operating system |
| What is an independent process? | A process whose execution is deterministic, reproducible, and can be stopped and restarted without ill effects |
| What is a cooperating process? | A process that can affect or be affected by other processes, sharing data with other processes |
| What is the objective of multiprogramming? | To have some process running at all times to maximize CPU utilization |
| What is throughput? | The amount of work the system accomplishes in a given time interval |
| What is a job queue? | A queue consisting of all processes in the system |
| What is a ready queue? | A queue containing processes residing in main memory that are ready and waiting to execute |
| What is a long-term scheduler? | Selects processes from secondary storage and loads them into memory for execution, controls the degree of multiprogramming |
| What is a short-term scheduler? | Selects processes from among those ready to execute and allocates the CPU to one of them |
| What is a medium-term scheduler? | Removes processes from memory to lessen the degree of multiprogramming, known as swapping |
| What is non-preemptive scheduling? | Once the CPU is allocated to a process, it keeps the CPU until it releases it by terminating or switching states |
| What is preemptive scheduling? | Divides time slots of CPU to a given process, allowing interruption of the current process |
| What is CPU utilization? | A measure of how busy the CPU is, ranging from 0 to 100 percent |
| What is throughput? | The amount of work completed in a unit of time, the number of jobs processed per time unit |
| What is turnaround time? | The interval from the time of submission to the time of completion of a process |
| What is waiting time? | The total amount of time a process spends waiting in the ready queue |
| What is response time? | The time from the submission of a request until the system makes the first response |
| What is First-Come First-Served scheduling? | The simplest CPU-scheduling algorithm where the process that requests the CPU first gets the CPU first |
| What is Shortest Job First scheduling? | A scheduling algorithm where the CPU is assigned to the process with the smallest next CPU burst |
| What is priority scheduling? | A scheduling algorithm where each process is assigned a priority, and the process with highest priority is executed first |
| What is Shortest Remaining Time First scheduling? | A preemptive SJF algorithm that preempts the currently executing process when a new process arrives with a shorter next CPU burst |
| What is Round-Robin scheduling? | A scheduling algorithm where each process gets a small unit of time called a time quantum, with the ready queue treated as a circular queue |
| What is a time quantum? | A small unit of time in Round-Robin scheduling, also called time slice |
| What is virtual memory? | A technique that allows execution of processes that may not be completely in memory, allowing programs to be larger than physical memory |
| What is demand paging? | A paging system where the OS swaps only the necessary pages into memory, never bringing a page into memory until it is required |
| What is a page fault? | An event that occurs when a process tries to use a page that is not in physical memory, causing a trap to the operating system |
| What is the valid-invalid bit? | An additional bit in the page table set to valid if a page is in memory, and invalid if the page is in secondary storage |
| What is pure demand paging? | Never bringing a page into memory until it is required |
| What is locality of reference? | The principle that programs do not access a new page of memory with each instruction execution, with most execution time spent on repeated instructions |
| What is page replacement? | The operating system removes or replaces one of the existing pages in memory to give way for an incoming page |
| What is a victim frame? | The frame selected by a page-replacement algorithm to be replaced |
| What is a modify bit or dirty bit? | A bit set whenever any word or byte is written into, indicating that the page has been modified |
| What is First-In First-Out page replacement? | The simplest page-replacement algorithm where the oldest page is chosen when a page must be replaced |
| What is Belady's Anomaly? | An instance where the page-fault rate may increase as the number of physical memory frames increases |
| What is the Optimal page replacement algorithm? | An algorithm that replaces the page that will not be used for the longest period of time |
| What is Least Recently Used page replacement? | An algorithm that replaces the page that has not been used for the longest period of time |
| What is address binding? | The process of mapping from one address space to another address space |
| What is compile time address binding? | Address binding where absolute addresses are generated during compilation |
| What is load time address binding? | Address binding where relocatable addresses are generated, translated to absolute addresses by the loader |
| What is execution time address binding? | Address binding used when a process can be moved from one memory to another during execution |
| What is dynamic loading? | A routine is not loaded until it is called, with all routines kept on disk in a relocatable load format |
| What is dynamic linking? | Libraries are linked at execution time, allowing program code size to remain small |
| What is a logical address? | An address generated by the CPU |
| What is a physical address? | An address seen by the memory unit |
| What is the Memory Management Unit? | A hardware device that performs run-time mapping from logical to physical addresses |
| What is memory allocation? | The process of reserving a partial or complete portion of computer memory for the execution of programs and processes |
| What is single partition allocation? | A memory management technique where some memory is set aside for the OS and the user program gets the rest |
| What are fixed partitions? | The oldest technique to put more than one process in main memory, with number of partitions fixed |
| What is first-fit allocation? | A memory allocation method where the first job claims the first available memory with space more than or equal to its size |
| What is best-fit allocation? | A memory allocation method where the OS allocates a job to the closest-fitting free partition in memory |
| What is fragmentation? | The problem where free memory space is broken into little pieces, preventing processes from being allocated to memory blocks |
| What is internal fragmentation? | Fragmentation that occurs when a partition is too big for a process |
| What is external fragmentation? | Fragmentation that occurs when a partition is available but too small for any waiting job |
| What is Multiple Variable Partition Technique? | A memory management technique where region sizes vary dynamically, with OS viewing memory as one large block called a hole |
| What is a hole? | One large block of available memory in variable partition technique |
| What is compaction? | The solution to external fragmentation that shuffles memory contents to place all free memory together in one large block |
| What is paging? | A memory management technique that permits a program's memory to be non-contiguous, dividing main memory into frames and processes into pages |
| What is a frame? | Fixed-sized blocks that main memory is divided into for paging |
| What is a page? | Blocks that a process is broken into for paging |
| What is a page table? | A table used to translate logical addresses to physical addresses in paging |
| What is segmentation? | A memory management technique where each job is divided into several segments of different sizes, each loaded into non-contiguous memory |
| What is a magnetic disk? | The bulk of secondary storage for modern computer systems |
| What is a track? | The logical division of a disk surface |
| What is a sector? | The subdivision of a track on a disk |
| What is a cylinder? | All the tracks on one drive that can be accessed without moving the heads |
| What is Constant Linear Velocity? | A disk reading method where density of bits per track is uniform, with more sectors on outer tracks |
| What is Constant Angular Velocity? | A disk reading method where number of bits per track is uniform, with disk rotation staying constant |
| What is physical formatting? | The process of breaking a new disk into sectors that the computer can understand |
| What is a bootstrap program? | The initial program that runs when a computer is powered up or rebooted |
| What is a bad block? | A block that becomes unreadable and not writable due to disk failure |
| What is a free-space list? | A list maintained by the system to keep track of free disk space |
| What is the bit vector method? | A free-space management technique where a single bit represents each block |
| What is the linked list method? | A free-space management technique where all free disk blocks are linked together with a pointer to the first free block |
| What is the grouping method? | A free-space management technique where addresses of n free blocks are stored in the first free block |
| What is the counting method? | A free-space management technique where the system keeps the address of the first free block and the number of free contiguous blocks |
| What is contiguous allocation? | A file allocation method where each file occupies a set of contiguous addresses on the disk |
| What is linked allocation? | A file allocation method where each file is a linked list of disk blocks |
| What is indexed allocation? | A file allocation method where pointers to blocks are grouped in one location called the index block |
| What is File Allocation Table? | A table with one entry for each disk block, used for linked allocation |
| What is disk scheduling? | The process where the OS improves average disk service time by scheduling requests for disk access |
| What is FCFS disk scheduling? | The simplest disk scheduling algorithm where requests are serviced in the order they arrive |
| What is SSTF disk scheduling? | Shortest Seek Time First, selects the request with the minimum seek time from the current head position |
| What is SCAN disk scheduling? | The read-write head moves from one end of the disk to the other, servicing requests as it reaches each track |
| What is C-SCAN disk scheduling? | Circular SCAN, moves head from one end to the other but immediately returns to the beginning without servicing on return trip |
| What is LOOK disk scheduling? | A version of SCAN where head is only moved as far as the last request in each direction |
| What is C-LOOK disk scheduling? | A version of C-SCAN where head is only moved as far as the last request in each direction |
| What is the act of fraudulently using email to try to get the recipient to reveal personal data? | Phishing |
| What is the capability of a system to fulfill its mission in the presence of attacks failures or accidents? | System Survivability |
| What is the verification that an individual trying to access a system is authorized to do so? | Authentication |
| What is the most extreme protection method where data is put into a secret code? | Encryption |
| What attack floods a target site with demands for data causing repeated unproductive tasks? | Denial of service |
| What intrusion allows unauthorized users to search through directories or files for information? | Browsing |
| What attack involves unauthorized monitoring or modification of a user’s transmission? | Wire tapping |
| What method refers to entering systems by guessing authentic passwords? | Repeated trials |
| What is an undocumented entry point installed by a programmer or diagnostician? | Trap doors |
| What attack uses discarded materials like disks CDs or printouts to gain system access? | Trash collection |
| What is the variation of phishing targeting a specific organization’s employees? | Spear phishing |
| What phishing attack uses SMS text messages? | Smishing |
| What phishing attack uses voice mail to trick victims? | Vishing |
| What program resides on computers attached to the network and examines passing data packets? | Sniffers |
| What attack disguises communication from an unknown source as a trusted source? | Spoofing |
| What malware disables a computer until a ransom is paid? | Ransomware |
| What set of programs allows administrator level access without the user’s knowledge? | Rootkits |
| What destructive program triggered by a specific event is called? | Logic bomb |
| What destructive program triggered by a specific time is called? | Time bomb |
| What science identifies individuals using biological characteristics like fingerprints or iris? | Biometrics |
Created by:
froguto7