Operating Systems Pre-midterms

Operating system

A program that controls the execution of application programs and is an interface between applications and hardware

processor

The operating system relinquishes the control of the _____________

executed

An operating system is a program that is _______________

1. Convenience

2. Efficiency

3. Ability to evolve

Objectives of an Operating System

• Application Programs

• Utilities

• Operating System

• Computer Hardware

What are the layers of a Computer System

Utilities and Operating System

Which layer of the OS does the programmer interact with?

Application Programs

Which layer of the OS does the end user interact with?

Computer Hardware

Which layer of the OS does the OS designer interact with?

1. Program development

2. Program execution

3. Access I/O devices

4. Controlled access to files

5. System Access

6. Error detection and response

7. Accounting

List the services provided by the OS

Nucleus

What is the other name for the kernel

main memory

The kernel is a portion of the operating system within the ____________________.

monitor

Job control is a special type of programming language that provides instruction to the _______________.

compiler, data

The job control language provides instructions on what _____________ and ______________ to use.

Memory protection

Which hardware feature does not allow the memory area containing the monitor to be altered?

Timer

Which hardware feature prevents a job from monopolizing the system?

Privilege instructions

Which hardware feature makes it so that certain machine-level instructions can only be executed by the monitor?

Interrupts

Which hardware feature was not present in early computer models?

User

Memory protection makes sure that user programs execute in __________ mode

System

Memory protection makes sure that monitor execute in __________ mode

Uniprogramming

Type of programming wherein the processor must wait for I/O instructions to complete before proceeding

Multiprogramming

Type of programming wherein when one job needs to wait for I/O, the processor can switch to another job

Batch Multiprogramming

What is is the usage of multiprogramming to handle multiple interactive jobs.

Time Sharing

Compared to Batch Multiprogramming, this minimizes processor use and commands are entered at the terminal.

Process

A ___________ is a program in execution.

An executable program, associated data needed by the program, execution context of the program

The three components of a process

Execution context

All the information the operating system needs to manage the process

Virtual Memory

Which part of the memory implements long-term storage

Files

Within the virtual memory, information is stored in named objects called ___________

Paging

Allows a process to be comprised of a number of fixed-size blocks

page number

The virtual address is a _______________ and an offset within the page

Main memory

Consists of a number of fixed-length frames, each equal to the size of a page.

Secondary memory (disk)

Can hold many fixed-length pages

Availability

Concerned with protecting the system against interruption

Confidentiality

Assuring that users cannot read data for which access is unauthorized

Data integrity

Give equal and fair access to resources

Authenticity

Discriminate among different classes of jobs

Efficiency

Maximize throughput, minimize response time, and accommodate as many uses as possible

System structure

The _______________ allows us to view the system as a series of levels.

Microkernel architecture

Assigns only a few essential functions to the kernel including address spaces, interprocess communication (IPC), and basic scheduling.

Multithreading

Divides a process into threads that can run concurrently.

Thread

Dispatchable unit of work that executes sequentially and is interruptable.

Distributed operating systems

Provides the illusion of a single main memory space and single secondary memory space

Object-oriented design

Enables programmers to customize an operating system without disrupting system integrity

Process Management

An Operating System’s fundamental task is ________________________

Program code (possibly shared), a set of data, a number of attributes describing the state of the process

A process consists of

process control block

It is created and processed by the operating system and allows support for multiple processes.

Trace

A list of the sequence of instructions that are executed.

Dispatcher

A small program that switches the processor from one process to another.

Not-running

In a two-state process model, the state may be in two states: running and _____________

Process Creation

The OS builds a data structure to manage the process

Process spawning

When the OS lets a running process create another.

Parent

The ______________ process is the original and creating process

Child

In process swapping, the _________ process is the new process

Interrupt

A HALT instruction generates an ___________ alert to the OS

HALT instruction

The way that a process can indicate its completion may be through a __________________ (1)

A user action (e.g. log off, quitting an application)

The way that a process can indicate its completion may be through a __________________ (2)

A fault or error

The way that a process can indicate its completion may be through a __________________ (3)

Parent process terminating

The way that a process can indicate its completion may be through a __________________ (4)

New

The first state of a five-state process model

Ready

The second state of a five-state process model

Running

The third state of a five-state process model

Blocked

The fourth state of a five-state process model

Exit

The fifth state of a five-state process model

Blocked

The state that follows after an event wait

Ready

When the process experiences a timeout, it returns to the ______________ state

Suspended

The blocked state becomes a ___________________ state when swapped to disk

Ready/Suspend

The state of a process (with two suspend states) when it fails to activate and reach the Ready state.

Block/Suspend

The state of a process (with two suspend states) when it fails to activate and reach the Blocked state.

Swapping

The reason for suspension where the OS needs to release sufficient main memory to bring in a process that is ready to execute.

Timing

The reason for suspension where the process may be suspended while waiting for the next time.

Memory tables

OS control structure used to keep track of both main and secondary memory.

I/O Tables

OS control structure used to manage the I/O devices and channels of the computer.

Files table

OS control structure that provides information about files.

File management system

Maintains the information within a file table

Process table

OS control structure used to know the details of the processes.

Process control block

The most important data structure in an OS because it defines the state of the OS.

Process image

The collection of program, e.g., data, stack, and attributes.

Process Identification

Category of process control block wherein each process is assigned a unique numeric identifier.

Processor State Information

Category of process control block that consists of the contents of processor registers.

Process Control Information

Category of process control block that consists of the additional information needed by the OS to control and coordinate the various active processes.

User mode, system mode

Most processors support at least two modes of execution, namely:

User mode

Mode of execution with less privilege.

System mode

Mode of execution with more privilege executed at the OS’ kernel.

Interrupt

Possible event where a process switch may occur.

Use: Reaction to an asynchronous external event

Trap

Possible event where a process switch may occur.

Use: Handling of an error or an exception condition

Supervisor call

Possible event where a process switch may occur.

Use: Call to an operating system function

Non-process Kernel

The operating system code is executed as a separate entity that operates in privileged mode.

administrator, supervisor, or root access

Highest level of privilege within the OS

prevent anything (user or process) from gaining unauthorized privileges

A key security issue in the design of any OS.

Masquerader

Outsider system access threat

Misfeasor

Insider system access threat

Clandestine user

Outsider or insider system access threat

Intrusion detection

Systems typically designed to detect human intruders and malicious software behavior.

Authentication

Has two stages: Identification and Verification

Access Control

A policy governing access to resources.

Auditing function

An ______________ monitors and keeps a record of user access to system resources.

Firewalls

Traditionally a dedicated computer that interfaces with computers outside a network and has special security precautions built into it to protect sensitive files on computers within the network.

Resource ownership

Process characteristic wherein process includes a virtual address space to hold process image.

Scheduling/execution

Process characteristic which follows an execution path that may be interleaved with other processes.