Operating Systems Tim Ji Lecture 1

1
Operating SystemsTim JiLecture 1

• Outline
• Course Information
• History of Operating Systems
• Basic Components of OS
• Lab 1
• Become familiar with Linux
• Readings
• Chapter 1

2
1 Course Information

• Official Course Outline
• On course webpage, MS Word document
• Course Objectives/Learning Outcomes
• Understand OS algorithms
• Be able to write multitasking programs with a
  variety of inter-process communication methods
• Be able to write scheduling, paging algorithms
• Textbook Tanenbaum, Modern Operating Systems
  2nd Edition, Prentice Hall

3
(No Transcript)
4
Course Information (2)

• Instructor
• Name Tim Ji
• Email tji AT conestogac.on.ca
• Office 2A503, x2230
• Office hour Drop by my office or by appointment
• Grading
• 3 tests, 20 each 60
• Assignments Labs 40
• Assignments
• Due in class at the end of lecture, 20 reduction
  in the assignment mark for each school day it is
  late.
• The assignments must be your own work.
  Cheating/copying other peoples files will result
  in both papers receiving zero.

5
Course Information (3)

• Labs
• Lab tasks will be demonstrated in the following
  week lab, and lab reports must be submitted by
  the end of the lab. You have 1 week to finish the
  lab task.
• Course website
• http//www.conestogac.on.ca/tji/os
• Announcements, assignments, lecture handouts,
  etc.
• Check it out at least once per day.
• Study to pass
• You have to pass both the tests portion and the
  assignments portion
• Assignments/Labs marking
• Demonstrate your task in lab
• Answer questions regarding to your own task
• Programming style of printouts of your source
  code, for programming assignments/labs

6
Introduction to Operating Systems

• Topics
• Role and purpose of the operating system
• History of operating system development
• Functionality of a typical operating system
• Learning Objectives
• Explain the objectives and functions of modern
  operating systems.
• Describe how operating systems have evolved over
  time from primitive batch systems to
  sophisticated multiuser systems.
• Describe the functions of a contemporary
  operating system with respect to convenience,
  efficiency, and the ability to evolve.

7
Early Computers

• First Computer
• Charles Babbage (1791-1871) designed the first
  true digital computer called the analytical
  engine.
• That was purely mechanical and intended to do
  math operations
• The engine was supposed to be made of brass, and
  steam powered
• He did not actually built the machine but
  inspired others in the field.

8
Early Computers

• Babbage also thought of the concept of software
• And hired the first programmer (Lady Ada,
  Countess of Lovelace) for his analytical engine

9
Current Computer Systems

• A computer system consists of
• hardware
• system programs
• application programs

10
What is an Operating System (1)

• Microsoft Glossary
• The software that controls the allocation and
  usage of hardware resources such as memory,
  central processing unit (CPU) time, hard disk
  space, and peripheral devices (like speakers or a
  mouse).
• The operating system is the foundation software
  on which programs, such as Word or Excel, depend.
  
• An example of an operating system is Microsoft
  Windows XP.

11
What is an Operating System (2)

• Provide a service for clients - a virtual machine
  (top-down view)
• An operating system is a layer of the computer
  system (a virtual machine) between the hardware
  and user programs.
• Multiple processes
• Multiple address spaces
• File system

12
What is an Operating System (3)

• Resource manager (bottom-up view)
• An operating system is a resource manager. 
  Resource management includes
• Transforming resources - to provide an easier to
  use version of a resource
• Multiplexing resources - create the illusion of
  multiple resources
• Scheduling resources - when and who gets a
  resource
• The hardware resources it manages include
• Processors - process management system
• Memory - memory management system
• I/O devices - I/O system
• Disk space - file system

13
What is an Operating System (4)

• The hardware resources are transformed into
  virtual resources so that an operating system may
  be viewed as providing a virtual computers, one
  to each user. A virtual machine (top down view)
  consists of
• Processes - virtualization of the computer
  including a virtual processor that abstracts the
  cpu - user mode instruction set system calls
• Virtual memory - virtualization of physical
  memory
• Logical devices - virtualization of physical
  devices
• Files - virtualization of disk space

14
What is an Operating System (5)

• The general functions of an operating system
• Allocation - assigns resources to processes
  needing the resource
• Accounting - keeps track of resources - knows
  which are free and which process the others are
  allocated to.
• Scheduling - decides which process should get the
  resource next.
• Protection - makes sure that a process can only
  access a resource when it is allowed
• Basic Functions
• Process management
• Resource management
• Device managment
• Memory management
• File management

15
History of Operating Systems (1)

• First generation 1945 - 1955
• Technology vacuum tubes plugboards
• Programming setting some switches
• Programming language machine language
• Tasks tables of sine, cosine, logarithms
• OS none

16
A Famous Remark

• "I think there is a world market for maybe five
  computers."
• Thomas Watson, chairman of IBM - 1943

17
History of Operating Systems (2)

• Second generation 1955 1965
• Technology Transistors
• Programming Punched cards
• Programming languages FORTRAN Assembly
• Tasks Scientific
• Computer Mainframes
• OS Batch system
• Universities started to buy computers (millions )

18
Early Batch System

• bring cards to IBM 1401 machine (good at card
  reading)
• read cards to tape
• put tape on IBM 7094 which does computing
• put tape on IBM 1401 which prints output offline

19
Famous Remarks

• "I have traveled the length and breadth of this
  country and talked with the best people, and I
  can assure you that data processing is a fad that
  won't last out the year.
• The editor in charge of business books for
  Prentice Hall - 1957

20
History of Operating Systems (3)

• Third generation 1965 1980
• Technology ICs
• Programming Punched cards
• Programming languages FORTRAN Assembly
• Tasks Scientific commercial
• Computers IBM 360, DEC PDPs
• OS Multiprogramming/timesharing, spooling
• OSes Developed
• MULTICS (father of all modern OSes)
• UNIX (System V, BSD)
• POSIX (by IEEE)
• MINIX (by Tanenbaum)
• Linux (derived from MINIX)

21
Famous Remark

• There is no reason anyone would want a computer
  in their home.
• Ken Olson, president, chairman and founder of
  Digital Equipment Corp. - 1977

22
History of Operating Systems (4)

• Fourth generation 1980-Present
• Technology VLSI
• Programming High level
• Programming languages C/C, Java,
• Computer PC
• OS Windows, MacOS, Linux
• Cheap PCs

23
Famous Remark

• We don't see Windows as a long-term graphical
  interface for the masses.
• A Lotus Software Development official, while
  demonstrating a new DOS version - 1989

24
The Operating System Zoo (1)

• Mainframe operating systems
• Room-size computers
• High I/O capacity
• Offers
• Batch processing (no interaction, such as large
  reports)
• Transaction processing (large number of small
  requests)
• Timesharing (multiple users sitting in front of
  clients)

25
Famous Forcast

• "Computers in the future may weigh no more than
  1.5 tons."
• Popular Mechanics, forecasting the relentless
  march of science, 1949

26
The Operating System Zoo (2)

• Server operating systems
• Offer services like print, file, or web
• UNIX, Windows 2000, Linux
• Multiprocessor operating systems
• Parallel computing
• Personal computer operating systems
• Single user with a good GUI, such as Windows 98,
  Windows 2000, Macintosh OS, Linux

27
The Operating System Zoo (3)

• Real-time operating systems
• E.g. industrial process control systems where
  each job must be completed in the specified time.
• Hard real-time (nuclear reactor control systems)
  or soft-real time systems (e.g multimedia
  systems) depending on the acceptance of missing
  deadlines
• Embedded operating systems
• Real-time systems with some resource constraints
  like memory, CPU, power.
• Smart card operating systems
• Extremely primitive OS running on credit card
  sized devices with a CPU.

28
Computer Hardware
Monitor
Bus

• Components of a simple personal computer

29
CPU

• Brain of the computer
• ALU (Arithmetical- Logical Unit)
• CU (Control Unit, fetch-execute-decode
  instructions)
• Has a certain set of instructions it can
  recognize and execute
• Basic CPU cycle
• Fetch the next instruction
• Decode it to determine its type and operands
• Execute it
• ..
• Programs are list of instructions executed by the
  CPU
• When the computer powers up, CU of CPU starts the
  fetch-decode-execute cycle
• Instructions may be OS instructions or other
  programs

30
CPU Modes

• A bit in PSW controls the mode
• Kernel Mode
• CPU can execute every instruction in its
  instruction set
• CPU can use every feature of the hardware
• OS runs in kernel mode
• User Mode
• Only a subset of instructions can be run
• And a subset of hardware features are accessed
• Generally all instructions involving I/O and
  Memory protection are disallowed in that mode
• To obtain OS services, a user program must make a
  system call that traps into kernel mode and
  invokes the OS
• Trap instruction switches from user mode to
  kernel mode and starts the operating system
  (system calls and errors such as division by zero
  causes trap instructions)

31
Pipelining

• Parallelize the fetch, decode, execute sequence
• Three stage pipeline While executing
  instruction N, decode instruction N1, and fetch
  instruction N2
• What happens when a conditional branch occurs in
  an instruction?

32
CPU Pipeline

• (a) A three-stage pipeline (three instructions
  processed in 1 cycle)
• (b) A superscalar CPU (with multiple execution
  units)

33
Pipelining
Execute N Decode N1 Fetch N2
Fetch N
Execute N1 Decode N2 Fetch N3
Decode N Fetch N1
Execute N2 Decode N3 Fetch N4
Instruction N
Instruction N 1
Instruction N2
Instruction N3
Instruction N 4
One CPU Cycle
34
Memory Hierarchy (1)

• Typical memory hierarchy
• numbers shown are rough approximations

35
Memory Hierarchy

• Magnetic Tape
• Backup purposes and for storing very large data
  sets.
• One dimensional, only sequential access is
  possible
• Reliable (no tape crashes, or time based data
  corruption)
• Was the main data storage medium of the past
• Optic CDs
• Faster than tape
• Used for permanent storage (now rewritable)

36
Memory Hierarchy

• Magnetic disks
• Are faster than tapes and CDs
• They are the main storage medium these days
• Data stored in concentric cylinders
• Disk head moves in discrete steps
• Each position of the disk head identifies a track
  (divided into multiple sectors, typically 512
  bytes)
• Rotates continuously with a certain speed (e.g.
  7200 rpm)

37
Memory Hierarchy

• Disks and tapes are mechanical devices, therefore
  they are slow compared to (RAM and Cache)
• Main Memory (Random Access Memory)
• Volatile
• Much Much faster than magnetic disks but more
  expensive too
• Cache
• Faster than RAM and more expensive
• CPU requests first go to cache, and if they are
  there (cache hit) then fine, if not there (cache
  miss) then RAM is accessed
• There can be multiple cache levels
• Cache is divided into cache lines (usually 64
  bytes at each line)

38
Memory Hierarchy

• Registers
• They are the fastest accessible memory locations
• Placed at the CPU.
• They are usually of size 32 bits, or 64 bits
  depending on the CPU type

39
Memory Hierarchy

• Read Only Memory (ROM)
• Write once, read many times
• Low level I/O cards
• Code for starting the computer
• Electrically Erasable Rom (EEPROM)
• Non volatile
• Flash RAM
• Non volatile

40
Memory Hierarchy

• CMOS (Complementary Metal Oxide Semiconductor)
• Volatile but can be sustained with mother board
  battery for years.
• May give checksum errors when being corrupted
• Very small, 64 bytes.
• Holds the current time and date, configuration
  parameters (like which disk to boot from etc.)

41
Yet another famous quote!

• "640K ought to be enough for anybody."
• Bill Gates, 1981

42
I/O Devices

• An input device transfers data from a mechanism
  like keyboard, mouse, touch screen, or microphone
  into a CPU register. CPU will then store the data
  into Main Memory
• For output devices, CPU fetches the information
  from main memory to its registers and transfers
  this information via the bus to an output device
  like screen, speaker, or printer.
• Communication devices serial and parallel
  ports, infrared transmitter/receivers, wireless
  network cards, network interface cards

43
DISK
PRINTER
PRINTER CONTROLLER
DISK CONTROLLER
CPU
MEMORY CONTROLLER

• Device controllers have microprocessors.
• They can work in parallel.
• They can tell CPU when they are done.

MEMORY
44
How I/O Can Be Done

• Three methods
• Busy waiting through system call
• Interrupt
• DMA (Direct Memory Access)

45
Lab 1 Get Familiar with Linux

• Introduction to Linux
• Lab material is available on the course webpage
• Follow the lab task specifications -- your marks
  depend on it.

46
Readings

• Tanenbaum, Chapter 1