Chapter 2 (Operating System Overview) Flashcards
What are the three main OS objectives?
Convenience
Efficiency
Ability to evolve
What does it mean for an OS to have the ability to evolve?
Adapt to new features, changes, and updates
What does the OS provide?
Interface
T/F The OS acts to insulate the user or programmer from hardware details, making it easier to access and use the system
T
What are some services the OS may provide?
Program development Program execution I/O device access File access System access Error detection Accounting
What is ISA?
Instruction Set Architecture
What does the instruction set architecture do?
Defines the set of machine language instructions that a computer can follow
What is ABI?
Application Binary Interface
What does the application binary interface do?
Defines a standard for binary portability across programs
What is API?
Application Programming Interface
What does the application programming interface do?
Gives a program access to the hardware resources and services available in a system through the user ISA supplemented with high-level language library calls
How can a computer be viewed?
As a set of resources
What if applications had ownership of system resources?
Sharing resources would be difficult
T/F It is better to let the OS own the resources, so the OS decides which programs get which resources
T
What are the problems with users and applications interacting directly with the hardware?
Scheduling
Setup time
Users had access to the system one at a time, this could be called….
Serial processing
Machine utilization was also important because
Machines were expensive
What is a resident monitor?
A monitor program that resides in memory
How does a monitor increase efficiency?
Scheduling each job in turn automatically, and by reducing setup time through a JCL
What is JCL?
Job Control Language
What does a JCL do?
Specifies setup steps for the monitor
What are desirable hardware features to support a batch OS?
Memory protection
Timer
Privileged Instructions
Interrupts
What is memory protection hardware feature in a batch operating system?
Prevents the monitor from being overwritten
What is a time hardware feature in a batch operating system?
Prevents a job from monopolizing the system
What is privileged instructions hardware feature in a batch operating system?
Only the monitor can do certain things
What is interrupts hardware feature in a batch operating system?
Provides better way to handle transfer of control from the monitor to user programs
What two modes of operation does a processor normally support?
User mode
Kernel mode
What is user mode for a processor?
For user programs
What is kernel mode for a processor?
For the OS
T/F The user mode for a processor has no limitations
F, it does
T/F Some main memory and some CPU time is given to the monitor
T
What is uniprogramming?
Running one program at a time
T/F Multiprogramming is an extension of uniprogramming
T
T/F Batch systems run programs in the “background” and generally don’t have direct user interaction
T
Define a process
A program in execution
Processor is kept busy by switching between programs in response to events such as I/O activity
Multiprogrammed batch systems
Processor time is shared among a number of active users by giving each user a slice of time
Time-sharing systems
Supports applications written to perform a query or update against a database by a user, such as an airline reservation system
Real-time transaction systems
What are some problems with running multiple programs at the same time?
Improper synchronization
Failed mutual exclusion
Nondeterminate program operation
Deadlocks
What is Improper synchronization?
Need a reliable way for one program to wait on another
What is Failed mutual exclusion?
Need to prevent multiple programs from accessing a resource such as a file at the same time
What is Nondeterminate program operation?
Need program results to be independent of other programs running at the same time
What are deadlocks?
Need to avoid situations in which programs are waiting on each other
What parts does a process have?
Executable program
The data the program is using
Execution context
What is the execution context of a process?
Includes the information required by the OS to control the process
What are the requirements for multiple processes in memory?
Isolation
Automatic allocation and management
Support for modular programming
Protection and access control
Long-term storage
What is isolation in memory management?
Keep process from accessing or overwriting the memory of another
What is automatic allocation and management in memory management?
Programmer should not worry about memory mgmt
What is support for modular programming in memory management?
Create, destroy, alter size of modules dynamically
What is protection and access control in memory management?
Restrict or grant access as needed
What is long-term storage in memory management?
Persist after computer is off
What is virtual memory?
Allows a program to have a logical view of memory
T/F Virtual memory gives the program a view of memory that may be much larger than physical memory
T
A ____ swaps pieces of programs, called pages, that are the same size. This makes it easy to replace one piece with another
Paging system
What does a virtual memory address consist of?
Page number
Offset
What does the paging system do?
Maps the logical page to the physical page
T/F Pages are swapped from disk to main memory as the program runs
T
Protecting the system against interruption
Availability
Protecting against unauthorized access to data
Confidentiality
Protecting against unauthorized modification
Data integrity
Protecting against false identities
Authenticity
What are three factors to consider in scheduling?
Fairness
Differential responsiveness
Efficiency
What is fairness in scheduling?
Processes should get equal treatment (if same class and priority)
What is Differential responsiveness in scheduling?
may need to discriminate among different classes of jobs with different needs
What is Efficiency in scheduling?
maximize throughput and minimize response time
How may scheduling be implemented?
Queues of processes
A “____” queue contains processes currently in main memory
Short-term
A “____” queue contains processes waiting to run
Long-term
What are five categories of modern OS design?
Microkernel architecture
Multithreading
Symmetric multiprocessing
Distributed operating systems
Object-oriented design
T/F The kernel contains the most frequently used functions
T
What is monolithic kernel architecture?
All one piece
What is a microkernel architecture?
Assigns only a few essential functions to the kernel
What is a thread?
A dispatchable unit of work
T/F A process may have multiple threads of execution, where each thread belongs to the process and shares its resources, but executes independently and concurrently with other threads of the process
T
T/F Multithreading is more efficient than creating sperate processes
T
What is one way to manage several processors?
SMP
What characteristics do SMP systems have?
Multiple processors
These processors share the same main memory and I/O facilities
All processors can perform the same functions
T/F An SMP OS can schedule threads on any available processor in the system
T
What are the SMP Advantages Versus Uniprocessor
Performance
Availability
Incremental growth
Scaling
Multiple machines may be managed together with a distributed operating system
Distributed OS
T/F A distributed OS lags behind uniprocessor and SMP systems
T
Can object-oriented design techniques be applied to the operating system
Yes
What is MTTF?
Mean time to failure
What is MTTR?
Mean time to repair
How is availability calculated?
MTTF / (MTTF + MTTR)
Spatial redundancy
Multiple components
Temporal redundancy
Repeating an operation after an error occurs
Information redundancy
Use of error correction or detection techniques
Helps to prevent a fault in one application from affecting another
Process isolation
Helps ensure correct operation and detection of problems such as deadlock
Concurrency controls
Provides a greater degree of isolation as well as redundancy
Virtual machines
Save state so that recovery is possible in the event an error occurs
Checkpoints and rollbacks
