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Flashcards

OS Chapter 1 Flashcards

Joel Pearson Operating Systems English 39 cards

Cards in this deck (39)

  1. 1What are the four components of an operating system?1. The computer hardware
    2. The operating system
    3. System and Application programs
    4. Users
  2. 2Explain what it means for the OS to be a resource allocatorThe OS manages all the resources, and decides between conflicting requests in order to be efficient overall.
  3. 3Explain what it means for the OS to be a control programThe OS controls the execution of all the running programs, trying to prevent errors or improper use of the computer
  4. 4What is a "Kernel"?The one program that runs at all times on the computer. This is a possible definition for an Operating System.
  5. 5Does a solid, universal definition exist for Operating Systems?No, Operating systems can be understood to be:
    - The Kernel Itself
    -- The Kernel with System Programs
    -- Whatever the vendor ships when we asks for an Operating System (smart ass)
  6. 6What does a bootstrap program do?At the start up of the computer, the bootstrap program is booted to initialise all aspects of the system, and load the operating system kernel and start the execution.
  7. 7What is the difference between an interrupt and a trap/exception?A trap or exception is a software-generated interrupt caused by an error or the user request. An interrupt in general is usually caused by I/O
  8. 8What is the difference between main memory and secondary memory?MAIN MEMORY can be accessed directly by the CPU (Random access), and is volatile (not good for permenant storage).
    SECONDARY MEMORY is accessed by the disk (e.g. HDD or SSD) which is slower, but is also non-volatile.
  9. 9Recite the storage device heirarchy. What is the order based on? What is the different between the top 3 and the rest?-- (1) Registers, (2) Cache, and (3) Main Memory come first - these are access directly by the CPU. They faster to access.
    -- (4) SSD, (5) HDD, (6) Optical Disk, and (7) Magnetic tapes are slower, though faster types tend to be (understandably) more expensive.
  10. 10What are three advantages of multiprocessor (aka parallel / tightly coupled) systems?1. Increased Throughput
    2. Economy of Scale
    3. Increased Reliability
  11. 11What are two types of multiprocessor systems?-- Asymmetric Multiprocessing - each processor is assigned a specific task
    -- Symmetric Multiprocessing - each processor performs all tasks
  12. 12What is the difference between clustered and multiprocessor systems?Clustered systems are like multiprocessor systems, except the multiple systems can work togetehr
  13. 13What's the difference between Asymmetric and Symmetric clustering?Both relate to surviving failures of other nodes:
    - ASYMMETRIC: one machine is in 'hot-standby mode', ready to pick up on a failure
    - SYMMETRIC: all machines are running applications, monitoring each other.
  14. 14What's the difference between Timesharing / Multitasking and Multiprogramming / Batch System structures?BATCH SYSTEM: organises jobs (keeping a subset of jobs in memory) so CPU only has to execute one job at a time. It can switch to another job if it has to wait (e.g. for I/O)
    TIME SHARING: the CPU switches jobs frequently so users can interact with each job will it is running, creating interactive computing. (More detail later in course)
  15. 15What's the difference between a process and a program?A program is a passive entity, and a process is an active entity. Basically, a process is a program in execution. It needs access to memory, files, I/O, etc.
  16. 16What is the purpose of a program counter?To keep track of where a process is in it's execution. The counter specifies the location of the next instruction to execute.
  17. 17How many counters does a process have per thread?One
  18. 18Does all of a program and it's needed data need to be in the memory?No, a program requires "all or part of" it's instructions and reference data to be in the memory. Management management determines what we need in the memory and when.
  19. 19What are the key three activities of memory management?1. Keep track of which parts of the memory are currently being used and when
    2. Deciding what needs to be moved in and out of memory.
    3. Allocating and deallocating memory space as needed.
  20. 20What is the difference between protection and security?PROTECTION: any mechanism for controlling access of processes or users to resources defined by OS (basically, behave yourself)
    SECURITY: Defense of a system against internal or external attacks (e.g. viruses, theft, worms, etc.)
  21. 21Describe the traditional computing environmentStand-alone general purpose machines. The definition here is blurred as most systems interconnect with others.
  22. 22Describe the mobile computing environmentHandheld smartphones, tablets, etc... There are some extra features (e.g. touch screen, gyroscope), and allows new kinds of apps like augmented reality.
  23. 23Describe the Distributed Computing EnvironmentCollection of separate systems networked (commonly through TCP/IP networking via LAN, WAN, etc.) do work together to create the illusion of a single system.
  24. 24Describe the Client-Server computing environment. What to computer server and file server systems do?Many client PCs interfact with a server via a network. Many systems are now 'servers', responding to client requests.
    -- A COMPUTER SERVER system provides an interfaces to client to request services.
    -- A FILE SERVER system provides an interface for clients to store and retrieve files.
  25. 25Describe the P2P Environment. How does a node join a P2P environment?Peer-to-Peer environments don't distinguish between clients and servers. All nodes can act as either or both.
    When a node joins a P2P network it either registers it's service with the networks central lookup service, or broadcasts requests, and respond to requests via discovory protocol.
  26. 26Describe Virtual Computing EnvironmentsWhen an OS allows other operating systems to run within it either through emulators or virtual machines.
  27. 27What are real-time embedded systems?Most prevalent form of computers
  28. 28What are the three main purposes of an operating system?1. To provide an environment where the compute can execute programs efficiently and conveniently
    2. To allocate computer resources to solve the given problem in a fair and efficient way
    3. As a control program to manage (1) the operation and control of I/O devices, and (2) the execution of user programs to prevent errors or improper use
  29. 29OSs generally care about efficiency, but when is it okay to be 'wasteful'?Single user systems maximise the use of the system to benefit the user - 'wasting' is okay provided it can deliver the needed services.
  30. 30What is the main problem OS programmers face in trying to write an operating system for a real time environment?Keeping the OS within the fixed time contraints of a real time system: not completing a certain task on time can lead to critical failure. When writing an OS, the writer must be sure his scheduling schemes don't allow late responses
  31. 31Should the definition of an operating system extend to include web browsers and mail programs?It can provide performance advantages by taking advantage of the features on the kernel, but (1) applications are applications, not part of the OS, (2) any performance benefits would be offset by vulnerabilities, (3) it leads to a bloated operating system (which isn't fun, look at Windows)
  32. 32How does the distinction between kernel mode and user mode function as a rudimentary form of protection (security) system?Outside of kernel mode, the CPU has limited capability, thereby enforcing protection of critical resources.
  33. 33Which of the following instructions should be privileged (I.e. not performable in user mode)?: (a) Set timer value, (b) read the block, (c) clear memory, (d) issue a trap instruction, (e) turn off interrupts, (f) modify entries in device-status table, (g) switch from user to kernel mode, (h) access I/O deviceA, C, E, F, H. Standard encapsulation sense.
  34. 34Some early computers protected the operating system by placing it in a memory partition that could be modified by the user OR the operating system. Describe two difficulties with this.The data required by the operating system would have to be stored in or passed through unprotected memory, which would be vulnerable to unauthorized users.
  35. 35Some CPUs can provide for more than two modes of operation. What are two possible uses for these multiple modes?- A finer grained security policy.
    - Different distictions within kernel mode
  36. 36Timers could be used to compute the current time. Provide a short description of how this could be accomplishedRepeatedly set a timer for some time in the future and go. When awaked by interrupt, it could update it's local state which keeps track of the number of interrupts,
  37. 37Why are caches useful? What problems do they solve, and what do they cause? Why not just make a cache as large as a disk?-- Caches are useful when two or more components needs to exchange data but do so at different speeds. Caches can provide a buffer of intermediate speed so the fast device can find the data it needs without waiting for the slower device.
    -- Trouble is, the data in the cache needs to be kept consistent with the disks, which can be a problem on multi-processor systems where more than one process can be accessing a datum(?)
    -- A component can by elimitated by a cache provided the cache can save it's state in the same way, and if caches are affordable. Both are unlikely (/snark)
  38. 38What does firmware mean?Read only, can't be changed by the user at all
  39. 39What does ROM and EPROM stand for?ROM: Read Only Memory
    EPROM: Erasable Programming Read Only Memory
    Related to Firmware

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Operating Systems Flashcards on OS Chapter 1 Flashcards, created by Joel Pearson on 09/10/2018.
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Joel Pearson
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