Chapter I The Computer - Department of Computer Science

COSC 1306
Jehan-François Pâris
Chapter Overview
The computing phenomenon
 Pervasiveness
 Computers or computing?
Historical perspective
 Four predecessors
 The birth of computers
 Its evolution
Computers as life changers
They are everywhere
They have changed our lives
 Electronic mail
 Online order processing
 Ticketless travel
Case study
A friend of mine
was teaching in a
small university in
 He is now in a
university in El
Before the Internet, his life would have been
 No access to a good university library
 Could only communicate with colleagues
 Expensive international calls
 Slow Uruguayan postal service
Nearly total isolation from CS community
He has
 Full access to research papers posted online
 Can communicate with colleagues through
 Email, instant messages, Facebook, …
 Skype
 Submits papers to conferences through
We write papers together!
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
Human contacts still count:
 Main reason why scientists travel
No Internet access means exclusion
 Case of most African countries
The iceberg
Most computing
takes place where
we do not see it
Car computers
Set-top box
Digital television
Fly-by-wire planes
Smart phones
Many medical appliances
An analogy
Mid-nineteenth century big textile factories used
 Steam-powered looms
One steam engine powered several looms
 Power went through transmission belts and
 Dangerous
transmission belts
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,
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
Are we now living in the best of all possible
Social problems
Lack of privacy
Nothing is forgotten
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'
How a series of simple computer errors
sabotaged a state-of-the-art medical wonder.
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.
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
The answer
It depends
 On Boeing planes, the pilot wins
 Great for airlines with highly-trained
 Not so good otherwise
 On Airbus planes, the computer wins
 Great for airlines with not-so-well-trained
 Pilots can still override computer
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 "
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?
The issues
Disk failures:
 Hard to figure exact mean time to fail of
hard drives
One hundred thousand to one million
One hundred thousand hours is slightly
more than 11 years
An array of 150 disks will experience an
average of one failure per month
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?
Can you read these?
On an old PC
But you can still read this
And this
Or even this
The Senate and the people …
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”®
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
Three stages
The ancestors
The pioneers
The continuation
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
Blaise Pascal
Seventeenth-century French
physicist, Christian polemist
and philosopher
His contribution
 First adding machine
 He patented it!
La machine de Pascal
Could only add and subtract
Costly to build
Not a commercial success
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
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
Jacquard loom
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
Charles Babbage
English mathematician and
mechanical engineer
Proposed a mechanical
calculator that could
tabulate polynomial
 Not built until much later
Polynomials were used—and are still used—to
compute logarithms, sinus, cosines and so on
 Boole wanted to speed up the computation of
numerical tables
The differential engine
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
Showed that computations can be programmed
Samuel Morse
American painter and inventor
Invented the telegraph
 First practical application of
 "Queen Victoria's Internet"
Huge immediate impact on
many human endeavors
 Made the world smaller
Long-term impact
Was developed to avoid continued fighting after
peace treaty (Treaty of Ghent 1814)
 Did not guarantee universal peace among
Showed that information could travel fast over
long distances
Herman Hollerith
American statistician
Tried to speed up
the processing of the
1890 census
Invented the
tabulating machine
Tabulating machine and sorter
How they worked (I)
Used punched cards
 Hollerith cards
 Became obsolete in the late seventies
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
Long-term impact
Tabulating machines were produced until the
 Were used all around the world
 Made IBM
While Babbage’s differential engine was purely
mechanical, Hollerith tabulating machines were
More inventors (I)
Charles Sanders Pierce
 American philosopher, logician and inventor
 Showed in 1880’s that Boolean algebra could
be implemented by electrical circuits
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
Boolean algebra and circuits
Switch on is 1, switch off is zero
More inventors (II)
John Atanasoff and Clifford Berry
 Iowa State College
 Built a very limited computer using vacuum
tubes in the 1930’s
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
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
 Executed them in sequence
 Loops were implemented by making a paper
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
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)
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
Binary arithmetic
Used by all computers
Two-digit arithmetic
 0 and 1
 Easier to implement
 Two voltages HIGH and LOW
Binary numbers
0 same as decimal 0
1 same as decimal 1
10 same as decimal 2
11 same as decimal 3
100 same as decimal 4
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
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
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
Binary addition and multiplication
1 + 1 = 10
The Von Neumann architecture
Memory containing program and data
 Datapath
 Control
Storage subsystem came later
A single bus realization
A more recent realization
Northbridge chip is
much faster than
Southbridge chip
Trend is to include the
functionality of the
Northbridge in the CPU
 Intel
Sandy Bridge
 AMD Fusion
A laptop motherboard
Used vacuum tubes
 Were power hungry and unreliable
 First commercially successful computer
 Well established tabulating machine maker
 Started dominating the field in the mid to
late fifties
Overall organization
Quite similar to that of today’s computers
programs + data
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
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
An IBM 1401
Interactive systems
Came later
Allow users to interact with the OS through their
Include an interactive command language
 UNIX shells, Windows PowerShell
 Can also be used to write scripts
Time sharing (I)
Lets several interactive users to access a single
computer at the same time
Standard solution when computers were
Time sharing (II)
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
The fathers of UNIX
Ken Thompson and Denis Ritchie
Became the standard operating systems for
 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
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
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
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
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
Xerox PARC (I)
Founded by XEROX in 1970
 Laser printing
 Ethernet
 The GUI paradigm
 Object-oriented programming (Smalltalk)
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
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
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)
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
How IBM lost the PC market
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
How IBM lost the PC market
Chip makers learned to produce functionally
equivalent BIOS without violating IBM
 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
How IBM lost the PC market
Rivals could sell PCs at cheaper prices than
 Leaner cost structure
Could come with new models faster than IBM
 Less cumbersome review process
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
 Now competing with ARM chips
Digital divide