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Transcript
Q: The following statement explains which structure?
“Used for high-speed I/O devices able to transmit information at speeds close to memory
speeds”
A: Direct access memory structure.
Q: In direct access memory structure, what is the function of the DEVICE
CONTROLLER?
A: Device controller transfers blocks of data from buffer storage directly to main memory
without CPU intervention
Q: In direct access memory structure, a number of interrupts equal to the number of
blocks of data is needed to be generated to access this block of data, (T/F)
A: False
Q: In direct access memory structure, ONLY ONE interrupt is generated per block, rather
than the one interrupt per byte, (T/F)
A: True
Q: Draw a hierarchy showing the memory structure. Indicate the highest and the slowest
speeds.
A:
Q: Consider Von Neumann architecture, explain how the instruction is executed in three steps.
A:
1. Fetch instruction from memory into IR, Instruction Register
2. Decode the instruction. Fetch operands if needed and store them in some
internal registers.
3. Execute the instruction. Store results, if any, back to memory.
Q: Ideally, we want the programs and data to reside in main memory permanently. This
arrangement usually is not possible. Why?
A: For the following two reasons:
1. Main memory is usually too small to store all needed programs and data permanently.
2. Main memory is volatile storage device that loses its contents when power is turned off
or otherwise lost.
Q: What are the two characteristics of main memory?
A:
o Main memory – only large storage media that the CPU can access directly
 Random access
 Typically volatile
Q: Secondary storage – extension of main memory that provides large nonvolatile storage capacity
(T/F)
A: True
Q: Magnetic disks – rigid metal or glass platters covered with magnetic recording material, (T/F)
A: True
Q: In magnetic disks, disk surface is logically divided into tracks, which are subdivided into sectors, (T/F)
A: True
Q: What is the function of the disk controller?
A: The disk controller determines the logical interaction between the device and the computer
Q: How is the storage system is organized?
A: Storage systems is organized in hierarchy of: Speed, Cost and Volatility
Q: Define the concept of caching?
A: Caching is copying information into faster storage system; main memory can be viewed as a cache for
secondary storage
Q: Important principle, performed at many levels in a computer (in hardware, operating system,
software) (T/F)
A: True
Q: Explain how the caching is done?
A: In two steps:
1. Information in use copied from slower to faster storage temporarily
2. Faster storage (cache) checked first to determine if information is there:
 If it is, information used directly from the cache (fast)
 If not, data copied to cache and used there
Q: Define a process?
A: A process is a program in execution. It is a unit of work within the system.
Program is a passive entity, process is an active entity.
Q: What are the resources the process needs to accomplish its task?
A: CPU, memory, I/O, files and data initialization
Q: What does process termination require?
A: Process termination requires reclaiming of any reusable resources
Q: What is the function of the program counter?
A: The program counter specifies the location of the next instruction to execute.
Q: How many program counters does the single-threaded process have?
A: Single-threaded process has one program counter.
Q: How about the multi-threaded process?
A: Multi-threaded process has one program counter per thread
Q: Typically system has many processes, some user, and some operating system
running concurrently on one or more CPUs (T/F)
A: True
Q: In process management, what activities the operating system is responsible
for?
A: The operating system is responsible for the following activities in connection
with process management:
• Creating and deleting both user and system processes
• Suspending and resuming processes
• Providing mechanisms for process synchronization
• Providing mechanisms for process communication
• Providing mechanisms for deadlock handling
Q: In memory management, what activities the operating system is responsible
for?
A: Memory management activities:
1. Keeping track of which parts of memory are currently being used and
by whom
2. Deciding which processes (or parts thereof) and data to move into
and out of memory
3. Allocating and de-allocating memory space as needed
Q: In storage management, OS provides uniform, logical view of information storage,
(T/F)
A: True
Q: Abstracts physical properties to logical storage unit, the file. (T/F)
A: True
Q: Each medium is controlled by device (i.e., disk drive, tape drive), (T/F)
A: True
Q: What are the varying properties of storage devices?
A: Varying properties include access speed, capacity, data-transfer rate, access
method (sequential or random)
Q: In file-system management, Files usually organized into directories, (T/F)
A: True
Q: What does access control do?
A: Access control on most systems determines who can access what
Q: In file system management, what activities the operating system is responsible
for?
A: OS activities include
 Creating and deleting files and directories
 Primitives to manipulate files and directories
 Mapping files onto secondary storage
 Backup files onto stable (non-volatile) storage media
Q: In which case do we need to use mass storage (disks)?
A: Usually disks used to store data that does not fit in main memory or data that
must be kept for a “long” period of time
Q: Disk subsystem determines the system overall speed, (T/F)
A: True
Q: In disk management, what activities the operating system is responsible for?
A: OS activities in disk management are:
1. Free-space management
2. Storage allocation
3. Disk scheduling
Q: What does WORM stand for?
A: It stands for write-once, read-many-times … example: ROM
Q: What does RW stand for?
A: It stands for read-write … example: RAM
Study the following material hard……..
Performance of Various Levels of Storage
Migration of Integer A from Disk to Register
• Multitasking environments must be careful to use most recent value, no
matter where it is stored in the storage hierarchy
• Multiprocessor environment must provide cache coherency in hardware
such that all CPUs have the most recent value in their cache
• Distributed environment situation even more complex
– Several copies of a datum can exist
Various solutions are out there!!
I/O Subsystem
• One purpose of OS is to hide peculiarities of hardware devices from the
user
• I/O subsystem responsible for
Memory management of I/O including buffering (storing data
temporarily while it is being transferred), caching (storing parts of
data in faster storage for performance), spooling (the overlapping of
output of one job with input of other jobs)
General device-driver interface
Drivers for specific hardware devices