COMP 225 - TEST 1

User Mode

a mode that provides an interface between an application and the OS, and only has access to hardware resources through the code running in kernel mode.

Top Down View

provide abstractions to application programs

Bottom Up View

Manage pieces of a complex system, orderly and controlled allocation of these resources

Resource Management Goals

Keep track if which programs are using which resources, mediate conflicting, requests from different programs and users

Time sharing

allocation of CPU to a program for short period, reallocate CPU to other program for short period

Space sharing

store parts of several programs in memory

Different generations of operating systems

First Generation (1945-55) vacuum tubes
Second Generation (1955-65) transistors and batch systems
Third Generation (1965-1980) ICS and Mulitprogramming
Fourth generation (1980-present) personal computer
Fifth Generation (1990-present) mobile computers

Programming in First Generation

Done by wiring up electrical circuits by connecting thousands of cables to plugholes to control machines basic functions, vacuum tubes used as switches (turned on or off in a circuit)

Batch System

a type of system developed for the earliest computers that used punched cards or tape for input, which were entered in a "batch"

Spooling

Simultaneous Peripheral Operation On-Line, reads jobs from cards onto disk when brought in.

Transistors

invented by Bell Laboratories in 1947, these tiny pieces of technology, which receive and amplify radio signals, make portable radios possible

MULTICS

Multiplexed Information and Computing Service

Minicomputers

type of computer that is designed to serve multiple users and process significant amounts of data; larger than a microcomputer, but smaller than a mainframe

UNIX

An operating system originally conceived in 1969 by Ken Thompson and Dennis Ritchie of AT&T's Bell Labs. In 1974, the UNIX code was rewritten in the standard programming language C. Today there are various commercial versions of UNIX.

Linux

an open-source version of the UNIX operating system

Processors

1. Fetches instructions from memory
2. Decodes the instruction
3. Executes instruction
Cycles until program finishes

Registers

Fast accessing storage inside the CPU
- no delay accessing any data
- least amount of space

Special Registers

-Program Counter (Address of next instruction)
-Stack Pointer (Address of top of stack)
- PSW (Program Status Word) various control bits

Multithreaded Chips

More transistors
-greater parallelism
-more cache
-deeper pipelines
-switch between threads in nanoseconds

Multicore Chips

-Each core has its own independent cpu
- allows for true parallelism

Memory Hierarchy

Cache Memory

a type of high-speed memory that a processor can access more rapidly than main memory
- main memory is divided into cache lines

L1 Cache

-inside CPU
-typically 16KB

L2 Cache

- inside CPU
-holds several megabytes
-takes one of two clock cycles to fetch

L3

- outside CPU on mother board
- feeds L2
- faster than main memory

Caching System Issues

- When to put a new item into the cache.
- Which cache lines to put the new item in.
- Which item to remove from the cache when a slot is needed
- Where to put a new evicted item in the larger memory

Main Memory

stores data and information and is usually volatile; data written and read in same amount of time regardless of location

ROM

Read Only Memory- Permanent instructions that cannot be changed.
- non-volatile
- contains bootstrap loader to start PC
- fast, inexpensive

EEPROM

Electronically Erasable Programmable Read Only Memory
- can be erased and rewritten per bytes
- non-volatile

Flash Memory

a type of EEPROM
- can be erased and rewritten in larger chunks

CMOS

complementary metal-oxide semiconductor
- volatile
-holds current time and date

Disks

a memory device consisting of a flat disk covered with a magnetic coating on which information is stored
- 1000 times slower than RAM
- Metal platters rotate at 7200 RPM
- Mechanical arm pivots over platters
- reading and writing

Solid State Disks

- Stores data in flash memory
- Less capacity than hard drives

Virtual Memory

- Possible to run programs larger than physical memory of computer
- Brings in the idea of caching
- Carried out by Memory Management Unit (part of CPU)

Controller

chip or set of chips that physically controls the device
- accepts command from operating system
-offers interface to operating system.

Device Driver

software gives commands and accepts responses, and interacts with controller.

3 Ways Driver is loaded

- Relink kernel with new driver, reboot
- Make entry into OS file telling OS to find driver and load when booted
- OS Loads driver, no reboot needed

Steps in I/O

- User make call for I/O
- Driver takes over
- Polls device to see when completed
- When completed driver deals with data
- Operating system returns control to user
- BUSY WAITING

Interrupts

device signals when complete

Buses

Communication system that transfers data between components inside a computer.

PCIe

- dedicated point to point connection
- serial bus architecture

DMI

Bus that connects hub of legacy devices to CPU
fast enough for:
-hard drive
- USB
- Ethernet
- legacy devices

Plug and Play

technology that allows a hardware component to be attached to a computer so that it is automatically configured by the operating system, without user intervention

BIOS (Basic Input/Output System)

-contains low level I/O software
-detects how much ram is installed
-detects I/O devices installed and operating
-new devices are configured
-determines boot device (usually hard disc)
-operating system read in and started
-devices drivers loaded into kernel

Mainframe Operating Systems

Room size computers
offers 3 kinds of server
-batch system-process without user interrupt
-transaction process - handles large numbers
-time sharing - allows multiple remote users

--specialized operating system used to run Mainframe

Server Operating Systems

serve multiple users at once
allowing sharing or resources
-FreeBSD
-LINUX
-Database

Kernel Mode

- operating system can execute every instruction
- operating system can use every hardware feature

Operating System

system software that acts as a "go-between", allowing computer hardware and other software to communicate with each other, provides programmers with set of abstractions

Multiplexing

sharing resources by time or space

Multiprocessor Operating Systems

Multiple CPUs in one system
-Parallel computers
-multi-computers
-multiprocessors

Personal Computer Operating System

provide good support to one user

Embedded Operating Systems

A specialized OS that runs in various electronic devices
Very small, normally fits on a single chip
All software installed in ROM
Examples: GPS devices, ATMs, sensors, microwave ovens, etc.

Sensor-Node Operating Systems

-Networks of tiny computers
-Run on batteries - short lived
-Connect to base via radio transmission

Real-Time Operating Systems

requiring minimal user interaction, guaranteeing certain response times for particular computing tasks

Hard Real-time

task must be serviced by its deadline

Soft Real TIme

Missing a dealine is acceptable

Process

A program in execution

Address space

a memory location from 0 to some max, a set of addresses that a process can use to address memory

Process as container

reads and writes from to address space

Process Table

to keep track of all the processes, the scheduler maintains a block of information in main memory

Child Process

A process that was started by another process (parent process).

Pros of Address Space

-Multiple programs in memory at the same time
-Needs protection from other programs

Files

data stored in a container

Root Directory

the top of the file management structure

File Mounting

Allows user to specify path names to external storage medium

Special Files

makes i/o devices look like regular files so regular system calls can be used to read/write to them

Pipe

Pseudofile that connects two processes

process table

During multiplexing running process are suspended, it must be in the same state when restarted and must be saved

Child Process

a process created by another process

Address Space

multiple programs in memory at same time, done in hardware

virtual memory

Space on a hard disk or other storage device that simulates random access memory.

files

data stored in a container, grouped by directories, system calls exist to read and remove files

file mounting

allows user to specify path names to external storage medium

Metric Unit nano (n):

10^-9

Metric unit- Milli

10^-3

Metric Unit Micro

10^-6

Metric Unit Kilo

10^3

Metric Unit Mega

10^6

Metric Unit Giga

10^9

Metric Unit Tera

10^12

process creation 4 principal events

1. system initialization2. execution of a process creation system call by a running process3. a user request to create a new process4. initiation of a batch job

operating systems 2 main functions

providing abstractions to user programs and managing the computer's programs

system calls

is like making a special kind of procedure call, only system calls enter the kernel and procedure calls do not

Linux "ls" command

list files and directories

linux "cd" command

change directory

linux "cp file1 file2"

copy file1 and call it file2

linux "mv file1 file2" command

move or rename file1 to file2

linux "touch <name>" command

create an empty file

linux "rm file"

remove a file

linux "cat file"

display a file

linux "less file"

display a file a page at a time

linux "file <filename>"

find out what type of file it is = text, zip, jpg, etc.

linux "mkdir" command

make a directory

linux "rmdir" command

remove a directory

linux "sudo su-" command

switches over to the root account

linux "history" command

show all commands typed into terminal. saves up to 1000 commands in most linux versions

multiprogramming

CPU switches from process to process -> sequential processes; illusion of parallelism

running

using the CPU at that instant

ready

runnable; temporarily stopped to let another process run

blocked

unable to run until some external event happens