LQ1 - Operating Systems - Introduction

operating system

program that acts as an intermediary between a computer user and computer hardware

1. User

2. Application Programs

3. Operating System

4. Computer Hardware

4 components of a computer system

kernel

The one program that runs at all times on the computer

system program

a type of program that is associated with the operating system, but is not part of the kernel

application program

a type of program not associated with the operating system

middleware

a set of software frameworks that provide services to application developers

operating system

it is a resource allocator and control program that efficiently uses HW and manages user program execution

shared computers

they must keep all users happy

dedicated systems

although they have dedicated resources, they still frequently use shared resources from servers

mobile devices

are resource poor, but optimized for usability and battery life

device controllers

connects through common bus to provide access to shared memory

true

true or false: I/O devices and CPU can execute concurrently?

operating system device driver

is found in each device controller type, in order to manage it

CPU

moves data from/to main memory to/from local buffers

local buffer

Each device controller has a ____ ____

interrupt

transfers control to the interrupt service routine

interrupt vector

It contains the addresses of all the service routines. It is the typical way to transfer control to the interrupt service routine.

trap or exception

a software-generated interrupt caused either by an error or a user request

interrupt

an operating system is _____ driven

it stores the registers and the program counter

how does the operating system preserve the state of the CPU?

interrupt handling

determines which type of interrupt has occurred. In this process, separate segments of code determine what action should be take for each type of interrupt.

1. CPU: device driver initiates I/O

2. I/O controller: initiates the I/O

3. I/O controller: input ready, output complete, or error generates interrupt signal

4. CPU: receives interrupt, transfer control to interrupt handler

5. CPU: interrupt handler processes data, returns from interrupt

6. CPU: resumes processing of interrupted task

Enumerate the interrupt-drive I/O Cycle in the correct order

1. After I/O starts, control returns to user program only upon I/O completion

2. After I/O starts, control returns to user program without waiting for I/O completion

What are the two methods for handling i/o?

system call

After I/O starts, control returns to user program without waiting for
I/O completion.

____ _____ requests to the OS to allow user to wait for I/O completion

device-status table

contains entry for each i/o device, indicating its type, address, and state

I/O device table

OS indexes into __ ___ __ to determine device status and to modify table entry to include interrupt

main memory

only large storage media that the CPU can access directly

main memory

is typically volatile and random access (in the form of dynamic random-access memory [DRAM]).

secondary storage

extension of main memory that provides large nonvolatile storage capacity

hard disk drives (HDD)

rigid metal or glass platters covered with magnetic recording material

1. tracks

2. sectors

disk surface is logically divided into ___, which are subdivided into ___

non-volatile memory (NVM) devices

faster than hard disks

1. registers

2. cache

3. main memory

4. nonvolatile memory

5. hard-disk drives

6. optical disk

7. magnetic tapes

rank this according to the storage device hierarchy

• cache

• hard-disk drives

• magnetic tapes

• main memory

• nonvolatile memory

• optical disk

• registers

caching

copying information into faster storage system

device driver

for each device controller to manage I/O. It provides uniform interface between controller and kernel.

direct memory access structure

used for high-speed I/O devices to be able to transmit information at close to memory speed

device controller

transfers blocks of data from buffer storage directly to main memory without CPU intervention

direct memory access structure

under this structure, only one interrupt is generated per block, rather than the one interrupt per byte

bootstrap program

simple code to initialize the system, load the kernel

system daemons

services provided outside of the kernel

operating system

starts the system daemons

• software error

• system call

types of software interrupt

system call

request for operating system service

multiprogramming

organizes jobs (code and data) so CPU always has one to execute

job scheduling

In multiprogramming, how is the one job selected ran?

interactive computing

is created when CPU switches jobs frequently to the point that users can interact with each job while it is running

dual mode (user mode and kernel mode) operation

allows OS to protect itself and other system components

mode bit

provides the ability to distinguish when system is running user code or kernel code

System call changes mode to kernel, return from call resets it to user

How to prevent user from explicitly setting the mode bit to kernel?

privileged

only executable in kernel mode

timer

prevents infinite loop (or process hogging resources)

process

a program in execution; a unit of work within the system.

1. passive entity

2. active entity

program is a ____ _____, whereas process is an ____ ____

false

true or false: process termination does not require the reclaim of any reusable resources

program counter

single threaded process has one ____ ____ that specifies the location of the next instruction to execute

multi-threaded process

has one program counter per thread

process management

the operating system is responsible for the following activities in connection with ____ ____:

1. Creating and deleting both user and system processes

2. Suspending and resuming processes

3. Providing mechanisms for process synchronization

4. Providing mechanisms for process communication

5. Providing mechanisms for deadlock handling

true

true or false: to execute a program, all (or part) of the instructions must be in memory

memory management

determines what is in memory and when

memory management activities

includes:

• keeping track of which parts of memory are currently being used and by whom

• deciding which processes (or parts thereof) and data to move into and out of memory

• allocating and de-allocating memory space as needed

file

abstracts physical properties to local storage unit

access control

allows for the determination of who can access what

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

caching

information in use copied from slower to faster storage temporarily

false

true or false: must not be careful to use most recent value, no matter where it is stored in the storage hierarchy

cache coherency

multiprocessor environment must provide ____ ____ in hardware such that all CPUs have the most recent value in their cache

I/O subsystem

is responsible for

• memory management of I/O

• general device-driver interface

• drivers for specific hardware devices

protection

any mechanism for controlling access of processes or users to resources defined by the OS

security

defense of the system against internal and external attacks

user identities

include name and associated number, one per user

group identifier

allows set of users to be defined and controls managed, then also associated with each process and file

privilege escalation

allows user to change to effective id with more rights

virtualization

allows operating systems to run applications within other OSes

emulation

used when source CPU type different from target type. It is generally the slowest method.

interpretation

is used when computer language not compiled to native code

virtualization

OS natively compiled for CPU, running guest OSes which is also natively compiled

virtual machine manager

provides virtualization services

distributed systems

collection of separate, possibly heterogeneous, system networked together

network

is a communications path

TCP/IP

the most common network type

• Local Area Network (LAN)

• Wide Area Network (WAN)

• Metropolitan Area Network (MAN)

• Personal Area Network (PAN)

types of networks:

network operating system

provides features between systems across networks, wherein there is an illusion of a single system

false

most systems use a single general-purpose processor

true or false: most systems use multiple general-purpose processors

multiprocessor system

also known as parallel systems and tightly-coupled systems, they are systems which are growing in use and importance because of their increased throughput, economy of scale, and increased reliability.

asymmetric multiprocessing

a multiprocessor system with each processor assigned a specific task

symmetric multiprocessing

a multiprocessor system with each processor performing all tasks

clustered systems

• similar to multiprocessor systems, but with multiple systems working together.

• it provides high-availability service which survives failures

• it usually shares storage using storage-area network (SAN)

asymmetric clustering

a clustered system where there is one machine in hot-standby mode

symmetric clustering

has multiple nodes running applications, monitoring each other

traditional computing environment

• stand-alone general purpose machines

• it is blurred as most systems interconnect with others through the internet

portals

provide web access to internal systems

network computers (thin clients)

are like web terminals

wireless networks

mobile computers interconnect via ___ ____

mobile computing environment

• has OS features like GPS, gyroscope, and allows for augmented reality.

• IEEE 802.11 wireless or cellular data networks for connectivity

client server computing

dumb terminals supplanted by smart PCs, wherein system servers as a response to client requests

compute-server system

provides an interface to client to request services

file-server system

provides interface for clients to store and retrieve files

peer-to-peer

• another model of distributed system.

• it does not distinguish between clients and servers, instead all nodes are considered peers.

discovery protocol

nodes broadcast request for service and respond to requests for service via ___ ___

cloud computing environment

delivers computing, storage, even app as a service across a network