Chapter 2 (Operating System Overview) Flashcards by scott johnson

What are the three main OS objectives?

Convenience
Efficiency
Ability to evolve

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What does it mean for an OS to have the ability to evolve?

Adapt to new features, changes, and updates

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What does the OS provide?

Interface

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T/F The OS acts to insulate the user or programmer from hardware details, making it easier to access and use the system

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What are some services the OS may provide?

Program development
Program execution
I/O device access
File access
System access
Error detection
Accounting

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What is ISA?

Instruction Set Architecture

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What does the instruction set architecture do?

Defines the set of machine language instructions that a computer can follow

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What is ABI?

Application Binary Interface

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What does the application binary interface do?

Defines a standard for binary portability across programs

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What is API?

Application Programming Interface

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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

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How can a computer be viewed?

As a set of resources

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What if applications had ownership of system resources?

Sharing resources would be difficult

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T/F It is better to let the OS own the resources, so the OS decides which programs get which resources

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What are the problems with users and applications interacting directly with the hardware?

Scheduling

Setup time

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Users had access to the system one at a time, this could be called….

Serial processing

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Machine utilization was also important because

Machines were expensive

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What is a resident monitor?

A monitor program that resides in memory

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How does a monitor increase efficiency?

Scheduling each job in turn automatically, and by reducing setup time through a JCL

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What is JCL?

Job Control Language

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What does a JCL do?

Specifies setup steps for the monitor

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What are desirable hardware features to support a batch OS?

Memory protection

Timer

Privileged Instructions

Interrupts

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What is memory protection hardware feature in a batch operating system?

Prevents the monitor from being overwritten

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What is a time hardware feature in a batch operating system?

Prevents a job from monopolizing the system

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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

What is uniprogramming?

Running one program at a time

T/F Multiprogramming is an extension of uniprogramming

T/F Batch systems run programs in the “background” and generally don’t have direct user interaction

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

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

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

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/F Multithreading is more efficient than creating sperate processes

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

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

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