1. COSC 1306 COMPUTER SCIENCE AND PROGRAMMING
Jehan-François Pâris 1

2. CHAPTER I THE COMPUTER

3. Chapter Overview The computing phenomenon Pervasiveness
Computers or computing?
Historical perspective
Four predecessors
The birth of computers
Its evolution 3

4. THE COMPUTING PHENOMENON

5. Computers as life changers
They are everywhere
They have changed our lives
Electronic mail
WWW
Online order processing
Ticketless travel

6. Case study
A friend of mine now teaches in a small University in Montevideo, Uruguay

7. Then Before the Internet, his life would have been difficult
No access to a good university library
Could only communicate with colleagues through
Expensive international calls
Slow Uruguayan postal service
Nearly total isolation from CS community

8. Now He has Full access to research papers posted online
Can communicate with colleagues through
, instant messages, Facebook, …
Skype
Submits papers to conferences through WWW
We write papers together!

9. My point Internet has abolished distance
Inexpensive personal computers allow us to work virtually everywhere
Still need a good Internet connection
Changed the lives of computer scientists and mathematicians working in
Small colleges in the boondocks
Decent universities in developing countries

10. Counterpoint Human contacts still count:
Main reason why scientists travel
No Internet access means exclusion
Case of most African countries

11. The iceberg
Most computing takes place where we do not see it

12. Examples Car computers Set-top box Digital television
Fly-by-wire planes
Smart phones
Many medical appliances

13. An analogy Mid-nineteenth century big textile factories used
Steam-powered looms
One steam engine powered several looms
Power went through transmission belts and pulleys
Dangerous

14. transmission belts

15. An analogy (cont'd)
Stream engines were progressively replaced by electrical motors
Quickly found it was better to have one smaller motor per loom
Got rid of transmission belts
Allowed more flexible plant layouts
Now electrical motors are everywhere
Car power windows, razors, toothbrushes, …

16. How it applies Started with a few giant "electronic brains"
Replaced by time sharing computers and individual terminals
Moved to personal computers
Each of us is now likely to have several computing devices

17. Counterpoint
Are we now living in the best of all possible worlds?

18. Social problems
Lack of privacy
Distraction
Nothing is forgotten

19. More pressing problems
What happens when computers that control critical aspects of our lives go wrong?
In 1985 a Canadian-built radiation-treatment device began blasting holes through patients' bodies. How a series of simple computer errors sabotaged a state-of-the-art medical wonder. (

20. The full report An Investigation of the Therac-25 Accidents
Nancy Leveson, U of Washington Clark S. Turner, UC Irvine
IEEE Computer, Vol. 26, No. 7, July 1993, pp

21. Another big problem
In fly-by-wire planes, pilots’ inputs are handled by an on-board computer
What happens when pilots’ inputs conflict with safety rules implemented in the on-board computer?

22. The answer It depends On Boeing planes, the pilot wins
Great for airlines with highly-trained pilots
Not so good otherwise
On Airbus planes, the computer wins
Great for airlines with not-so-well-trained pilots
Pilots can still override computer

23. An outcome
On June 1, 2009 Air France flight 447 from Rio to Paris crashed in mid-Atlantic
Cause of crash was aerodynamic stall
Preceded by problems with speed sensors
Inquiry noted that "pilots had not been trained to fly the aircraft in manual mode "
447

24. A long-term problem
An increasing large number of documents are exclusively stored in digital format without any hard copy
Most of your recent pictures
Your grades
Will they survive as well as hard copies do?

25. The issues Disk failures:
Hard to figure exact mean time to fail of hard drives
Ten thousand to one million hours
Ten thousand hours is slightly more than 11 years
An array of 150 disks will experience an average of one failure per month

26. The issues (cont’d) Offline storage media become rapidly obsolete
Who can read a 5.25” floppy?
A 4 MB floppy?
A 100MB Zip disk?

27. Can you read these?
On an old PC No No

28. But you can still read this

29. And this

30. SENATVS POPVLSQ[UE] The Senate and the people …
Or even this
SENATVS POPVLSQ[UE] The Senate and the people …

31. That’s not all Hard copies were easy to authenticate
Type of paper and ink that were used
Typewriter font
Electronic forgeries are harder to detect
Can use digital signatures
Become easier to break over time
Pictures can be “Photoshopped”®

32. My conclusion We are not in the best of all possible worlds
Rolling clock backward is not possible
The genie is out the bottle!
Must understand the issues and push for action
Course will only help you with first part

33. HISTORICAL PERSPECTIVE

34. Three stages
The ancestors
The pioneers
The continuation

35. The ancestors Their contributions made computing possible
Blaise Pascal
Joseph Marie Jacquard
Charles Babbage
Samuel Morse
Herman Hollerith
All died well before computers were invented

36. Blaise Pascal
Seventeenth-century French physicist, Christian polemist and philosopher
His contribution
First adding machine
He patented it!

37. La machine de Pascal Could only add and subtract Costly to build
Not a commercial success

38. Long-term impact
Showed that arithmetic operations could be performed by mechanical devices
Proof of concept
People kept building and using mechanical computing machines until the late sixties

39. Joseph Marie Jacquard Self-taught French inventor
Invented in 1801 a mechanical loom that simplified the weaving of fabrics with complex patterns (brocade, damask, …)
Key idea was to use punched cards to store the patterns

40. Jacquard loom

41. Long-term impact Jacquard loom was quickly adopted
Reduced manpower needs for weaving of fabrics with complex patterns
Caused a workers' revolt in Lyon in 1831
Still in use today
Showed that information could be stored in a machine-readable form

42. Charles Babbage English mathematician and mechanical engineer
Proposed a mechanical calculator that could tabulate polynomial functions
Not built until much later

43. Motivation
Polynomials were used—and are still used—to compute logarithms, sines, cosines and so on
Boole wanted to speed up the computation of numerical tables

44. The differential engine

45. Long-term impact
Boole went on to design a much more ambitious analytical engine
Prototype of a modern computer
Some difference engines were built later
One was used to produce printed logarithmic tables
Showed that computations can be programmed

46. Samuel Morse American painter and inventor Invented the telegraph
First practical application of electricity
"Queen Victoria's Internet"
Huge immediate impact on many human endeavors
Made the world smaller

47. Long-term impact
Was developed to avoid continued fighting after peace treaty (Treaty of Ghent 1814)
Did not guarantee universal peace among nations
Showed that information could travel fast over long distances

48. Herman Hollerith American statistician
Tried to speed up the processing of the 1890 census
Invented the tabulating machine

49. Tabulating machine and sorter

50. How they worked (I) Used punched cards Hollerith cards
Became obsolete in the late seventies

51. How they worked (II) When tabulating machine read a card, it could
Add the values stored in some columns to one of its registers
Instruct the sorter to open one of its slots
Next step was to make cards move within tabulator and sorter without any human intervention

52. Long-term impact
Tabulating machines were produced until the mid-seventies
Were used all around the world
Made IBM
While Babbage’s differential engine was purely mechanical, Hollerith tabulating machines were electromechanical.

53. More inventors (I) Charles Sanders Pierce
American philosopher, logician and inventor
Showed in 1880’s that Boolean algebra could be implemented by electrical circuits

54. Boolean algebra Uses two quantities (0 or 1; true or false)
Basic operations include
AND: p AND q is true iff both p and q are true
OR: p OR q is true unless both p and q are false
NOT: NOT p is true if p is false and false otherwise

55. Boolean algebra and circuits
Convention: Switch on is 1, switch off is zero
AND:
OR:

56. More inventors (II) John Atanasoff and Clifford Berry
Iowa State College
Built a very limited computer using vacuum tubes in the 1930’s

57. World War II
United States had to build very quickly large armed forces
Train and equip them
Needed better ballistic tables to predict naval gun trajectories
Resulted in development of two computers

58. Harvard Mark I Designed by Howard H. Aiken
Built by IBM from switches, relays and other electromechanical parts
First programmable computer
Read its instructions from a punched paper tape
Executed them in sequence
Loops were implemented by making a paper loop

59. ENIAC Electronic Numerical Integrator And Computer
Designed and built at University of Pennsylvania by a team headed by John Mauchly and J. Presper Eckert
Used vacuum tubes
Thousand times faster than Harvard Mark I
Came too late to contribute to war effort
Needed to be programmed externally

60. EDVAC Successor to ENIAC Designed by same authors
Used binary arithmetic
Simpler
Stored its programs in its memory
Could even modify them while running
(Von Neumann architecture)

61. Other WW II Computers
Set of top secret machines developed in UK to crack German Enigma code
Collectively known as Colossus
Existence was not known until much later

62. Binary arithmetic Used by all computers Two-digit arithmetic 0 and 1
Easier to implement
Two voltages HIGH and LOW

63. Binary numbers 0 same as decimal 0 1 same as decimal 1
1K = 1 followed by ten zeroes, same as 1,02410
1M = 1 followed by twenty zeroes  a million
1G = 1 followed by thirty zeroes  a billion

64. Deciphering decimal numbers
Both digit value and position count
937
Rightmost value indicates units
Value at its left indicates tens
Leftmost value indicates hundreds
We read 937 as nine hundred thirty-seven

65. Deciphering binary numbers
Both digit value and position count
110
Rightmost value indicates units
Value at its left should be multiplied by 2
Leftmost value should be multiplied by 4
We read 110 as 0×1 + 1×2 + 1×4 = 6

66. Binary addition and multiplication
0 + 0 = = = = 10
0 × 0 = 0 0 × 1 = 0 1 × 0 = 0 1 × 1 = 1

67. The Von Neumann architecture
Input
Output
Memory containing program and data
Processor
Datapath
Control
Storage subsystem came later

68. A single bus realization

69. A more recent realization
Northbridge chip is much faster than Southbridge chip
Trend is to include the functionality of the Northbridge in the CPU chip
Intel Sandy Bridge
AMD Fusion

70. A laptop motherboard

71. THE FIRST GENERATION Used vacuum tubes
Were power hungry and unreliable
UNIVAC
First commercially successful computer
IBM
Well established tabulating machine maker
Started dominating the field in the mid to late fifties

72. The UNIVAC I

73. Overall organization Quite similar to that of today’s computers CPU
MAIN MEMORY
programs + data
CPU
PERIPHERALS

74. Evolution Revolution was started by UNIVAC
IBM quickly become the leader
Was a true computer company
Well introduced in most businesses
Already used IBM tabulating machines
In the sixties and seventies, most people identified IBM as “the” computer maker

75. Batch systems
Allow users to submit a batches of requests to be processed in sequence
Include a command language specifying what to do with the inputs
Compile
Link edit
Execute and so forth 75

76. An IBM 1401 76

77. Interactive systems Came later
Allow users to interact with the OS through their terminals:
Include an interactive command language
UNIX shells, Windows PowerShell
Can also be used to write scripts 77

78. Time sharing (I)
Lets several interactive users to access a single computer at the same time
Standard solution when computers were expensive 78

79. Time sharing (II)

80. UNIX (I)
Started at Bell Labs in the early 70's as an attempt to build a sophisticated time-sharing system on a very small minicomputer.
First OS to be almost entirely written in C
Ported to the VAX architecture in the late 70’s at U. C. Berkeley:
Added virtual memory and networking 80

81. Ken Thompson and Denis Ritchie
The fathers of UNIX
Ken Thompson and Denis Ritchie 81

82. UNIX (II) Became the standard operating systems for workstations
Selected by Sun Microsystems
Became less popular because
Two many variants
Berkeley BSD, ATT System V, …
PCs displaced workstations
Windows has a better user interface 82

83. UNIX Today Several free versions exist (FreeBSD, Linux):
Source code of these free versions is available at no cost
Ideal platform for OS research
UNIX/Linux-based kernels used by
Apple OS X and iOS operating system
Android operating systems
Chrome OS is barely modified Linux 83

84. Time sharing (III)
Time sharing become much less important by the end of the eighties
Personal computers became almost as cheap as terminals
Time sharing could not support graphical user interfaces

85. Why?
A graphical user interface must transfer a lot of data between the processor and the display unit
Cannot do it if distance exceeds a few feet
The workstation was born
Combines a computer with its display

86. Graphical user interfaces
Called GUIs (pronounced goo-eys): Macintosh, Windows, X-Windows, Linux
Require a dedicated computer for each user
Pioneered at XEROX Palo Alto Research Center
Popularized by the Macintosh
Dominated the market with Microsoft Windows 86

87. Xerox PARC (I) Founded by XEROX in 1970 Invented Laser printing
Ethernet
The GUI paradigm
Object-oriented programming (Smalltalk) 87

88. Xerox PARC (II)
All their inventions were brought to market by other concerns
Popular belief is that Xerox management blew it
In reality
Alto workstations were very expensive
Smalltalk was very slow
Group was too small to deliver a full system 88

89. The personal computer
By 1971, it was possible to put a very simple CPU on a single chip
Intel 4004 was a four-bit microprocessor designed for a desktop calculator
Followed by an 8-bit version 8008
Used to build very basic personal computers

90. Evolution (I) 1977: Apple ][ First widely successful mass-produced PC
Killer app was Visicalc spreadsheet
1981: IBM PC
Big success because people trusted IBM
Microsoft designed the OS (PC-DOS)

91. Evolution (II) 1984: Macintosh First mass-produced PC with GUI
Was not an instant success
Rescued by laser printer
1992: Windows 3.1
MSDOS + Windows 3.1 offered the first GUI solution for IBM PCs

92. How IBM lost the PC market (I)
IBM PC used “off-the-shelf” components
Microsoft retained the rights to sell PC-DOS to other computer makers (MS-DOS)
Sole specific part was BIOS
Very basic operating system stored in read-only memory
Loads MS-DOS/Windows in main memory
© IBM

93. How IBM lost the PC market (II)
Chip makers learned to produce functionally equivalent BIOS without violating IBM copyright
Reverse engineering:
Define IBM BIOS by all its outputs for all possible inputs
Hire people who had never seen the IBM BIOS to rewrite it

94. How IBM lost the PC market (III)
Rivals could sell PCs at cheaper prices than IBM
Leaner cost structure
Could come with new models faster than IBM did
Less cumbersome review process

95. The new frontiers Smaller devices:
Now-defunct PDAs, smart phones, tablets
Cheaper than PCs (but tablets)
Much bigger market
New microprocessor architectures:
Intel—and AMD—pulverized the competition (Motorola 68000, MIPS, PowerPC, Sun SPARC)
Now competing with ARM chips

96. Challenges
Openness
Digital divide
Addiction