Transcript Lecture 1 - Suraj @ LUMS

Tuesday, June 06, 2006
I hear and I forget,
I see and I remember,
I do and I understand.
-Chinese Proverb
Today
 Course Overview
 Why a course on operating systems?
 What is an operating system?
CS 381 : Operating Systems
 Course URL
http://suraj.lums.edu.pk/~cs381m05
 Folder on indus
\\indus\Common\cs381m05
 Website – Check Regularly: Course
announcements, Slides, Resources,
Policies …
 Course Outline
CS 381 : Operating Systems
 Several programming exercises will be
given throughout the course. The purpose of
these exercises will be to give students
practice in using the UNIX system calls,
library functions, and algorithms.
 The development environment will be C on
UNIX.
Assumptions
 Unix shell commands
 gcc, gdb, makefile
 Text editor emacs, vi
 C programming
Pre-requisites
 Computer Organization & Assembly
Language (CS 223)

Load registers, interrupts, DMA …
 Data Structures
What is an OS?
editor
browser
spreadsheet
compiler
OS
hardware
 Software between applications and reality: Makes reality
pretty!
 Abstracts the underlying hardware.
 Gives illusion of changing finite into (almost) infinite.
 Provides protection (from malicious or buggy
programs).
Components of a simple personal computer?
Components of a simple personal computer
Monitor
Bus
Operating System:
•Manages all the devices
•Provides users simpler interface to the
hardware
• Efficiency.
• Convenience, ease of use.
• Optimize utilization
• E.g. mainframes: expensive
• Fairness
Intermediary between a user of a computer and the computer
hardware.
Monitor
Bus
Extended Machine : Simpler Interface
Disk (Mechanical and Electrical components)
Disk I/O?
Monitor
Bus
Extended Machine : Simpler Interface
Disk I/O
•Instructions for loading device registers
•Motor On/Off, Speed, Movement of disk arm,
sectors/tracks …
•Different for different devices!
Hide Complexity
 E.g. File interface.
OS as Resource Manager
Orderly and controlled access,

Resolve conflicts
 Prevent illegal accesses
 Device I/O (Maintain queues)

E.g. Printers
 Sharing Resources


CPU (Time multiplexing)
Memory (Space multiplexing)
OS: Extended example of a complex system
Deal with complexity.
Millions of lines of code.
 Hardware and Operating Systems have
influenced each other.
Charles Babbage (1792-1871)


First analytical Engine
Purely mechanical
Vacuum Tubes (1945-55)




Calculating Engines
Entire rooms
Tens of thousands of Vacuum Tubes
(problems of burn outs)
Wiring up plug boards!
Seen a vacuum tube?
Vacuum Tubes (1945-55)
 Calculating Engines
 Entire rooms
 Tens of thousands of
Vacuum Tubes (problems
of burn outs)
 Wiring up plug boards!
Transistors (1955-65)


Reliability
FORTRAN Program
punched on cards
Problems:
•CPU idle time
•I/O speeds vs CPU
speeds (Mechanical
vs Electrical)
•Costly equipment
•What if a ; missed?
Transistors (1955-65)


Reliability
FORTRAN Program
punched on cards
Problems:
•CPU idle time
•I/O speeds vs CPU speeds (Mechanical vs
Electrical)
•Costly equipment
Early batch system




bring cards to 1401
read cards to tape
put tape on 7094 which does computing
put tape on 1401 which prints output
Mostly used for scientific and engineering calculations
• What if a ; missed?
 What if it runs over the cards of another
program?
 No protection between users
ICs and Multiprogramming (1965-1980)
•IBM 360 series: Software compatible
machines
•Enormous and complex operating
systems
•Costly machines
•Lead to multiprogramming
•CPU bound (scientific calculations)
•I/O bound
ICs and Multiprogramming (1965-1980)
•Software compatible machines
•Enormous and complex operating systems
•Costly machines
•Lead to multiprogramming
Protection
among
users!
Introduction of key techniques
 Multiprogramming
 Spooling (Simultaneous Peripheral
Operation On Line)
 From Batch systems to Timesharing
Introduction of key techniques (cont’d)
From Batch systems to Timesharing
 I/O “people’s speed”

Response time
 Memory management
 CPU scheduling
 Process Synchronization
MIT, Bell Labs and GE
“Machine that would support hundreds of
time sharing users”
MULTICS (MULTIplexed Information and
Computing Service)
 Ahead of time.
At Bell Labs …
One user version of MULTICS.
Developed into UNIX
Linus Benedict Torvalds
(August 1991)
“ I'm doing a (free) operating system (just a
hobby …) for 386(486) clones …”
 Linus himself didn't believe that his creation was
going to be big enough to change computing
forever.
 Linux version 0.01 was released by mid
September 1991, and was put on the net.
 Enthusiasm gathered around this project and codes
were downloaded, tested, tweaked, and returned to
Linus.
Personal Computers (1980 – Present)
 Large Scale Integration (LSI)
 Intel came with 8080 which became hugely
popular
 First microcontroller with disk

DOS (Disk Operating Systems)
• Seattle Computer Products
• MS-DOS (does not support multiprogramming)



Doug Engelbart (Mouse, GUI)
Apple GUI
Windows
Monitor
Bus
Disk I/O
•Commands and accepts responses
•Instructions for loading device registers etc.
•Different for different devices!
•Device drivers (by each controller manufacturer)
•One for each OS supported.
Device drivers
 Run inside the kernel.
 Dynamically loaded drivers.
Input/Output
 Controllers have registers for
communication
 Memory mapped I/O
 Separate I/O space
 Hybrid
Some design issues
I/O Space
 Special IN/OUT instructions (use of
assembly code)
Memory mapped
 Caching of device registers should not be
done!
 Multiple buses