OS Chapter 1

Device Driver (SW)

in the os for each device controller, manages th I/O and provides interface between controller (mouse key boear ect.) ant the OS or kernal

Registers and cashe

SRAM, very fast and large, volitile memory used for temporary storage

Main memory

DRAM smaller cost effective only large storage that the CPU can access directly, non volitile

secondary stoage

non volitile extension of main memory example is SSD- faster than hard disk, is more popular is light weight

storage hiearchy

speed, cost volititlity

cashing

copying info into faster storage system

storage device hirarchy

registers, cashe, MM, nonvolitile memory, hard disk drive, optical disk, mgnetic tapes

polling I/O direct access

CPU must wait after each I/O opperation (busy wait)

Interupt triggered I/O event

the CPU will not wait after each I?o rather when an IO opperation completes it will trigger this that halts the CPU

Direct Access Memory (DMA)

for large data transfer, moving directly from IO wiht out going thougth the CPU

trap

software generated interupt

interupt cycle

fetch → decode →execute →interupt? → fetch

interupt vector

contains all of the addresses of the interupt service routine (ISR)

interrupt service routine

a special type of subroutine or function that handles hardware interrupts.

maskable interupt

can be temperarily disbaled, imporatn if you want to defer the handling of an interupt

non maskable interupt

can not be disabled and must be served immeditly

single proccessor

single core small systems ie phone pr PC

multiporccessor

aka parrallell system or tighlty coupled, advantages are increased though put economy of scale and increased readibillity

asyemetric multiporccessing

each proccessot is assigned a spesific task

symetric multiprocessing

(most common) each processor preforms all tasks

clustered system

a group of independent computers CPUs that work together to achieve a common goal.

what does the os do

resource allocator, control program

kernal

the program that is always running aka the os

system programs (SP)

some of the services provided out side of the kernal, anythign not in the kernal but is in the OS, dependant on the type of OS

System daemons

what the SP are loaded into at boot time, run the entire time the kernal is running

SP types

1. File Management

• Examples: copy, rm, ls, mkdir (Unix)

2. Status Information

• Examples: ps (Unix: process status), who (Unix: user info), regedit (Windows)

3. File Editing

• Examples: Text editors

4. Programming Language Support

• Examples: cc (C compiler), javac (Java compiler)

5. Program Loading and Execution

• Examples: Loaders, debuggers

6. Communications

• Examples: ssh (secure connection), ftp (file transfer)

7. Application Programs

• Examples: Web browsers, games, electronic pages

dual mode

operations allows the OS to protect its self and other system components

user mode

unprotected mode bit = 1

kernal mode

protected aka privilaged mode, mode bit = 0

privilaged instruction

can cause harm if badly implemnted, only executable in kernal mode, if a system call is made in user mode the mode switches to kernal mode

privilage mode intruction exammples

• I/O instructions and Halt instructions.

• Turn off all maskable Interrupts.

• Set the Timer.

• Clear the Memory or Remove a process from the Memory.

• Modify entries in a Device-status table (port)

System call

a way for a program to request services or resources from the operating system

virtualization

allows different OSes to run on the same machine at the same time

Emulation

process of mimicking the behavior of one system on a different system

Virtual Machine Manager

uns the guest OSes, manages their resource use, and protects each guest from the others