Charles Babbage Difference Engine

Barcamb 2010Nathan Lisgo | Technical Director | Panoetic Ltd

Charles BabbageDifference Engines

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My background

• Nathan Lisgo

• BSc Hons Computing

• Web Developer for over 10 years

• PHP, MySQL, Javascript, Flash

• Sept 2009 joined Panoetic

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Objectives

• Bio of Charles Babbage

• His Quest

• Pioneer of the computer?

• Doron Swade takes up the baton

• World exclusive

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Charles Babbage • 1791 - 1871

• Age 8 recovered from life-threatening fever

• 1810 - Arrived at Trinity College, Cambridge

• 1812 - Founded Analytical Society with peers

• 1812 - Transferred to Peterhouse, Cambridge

• 1814 - Received honorary degree without examination

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Anything for science

• Baked himself in an oven at 265 F

• Lowering himself into the mouth of a volcano

• Walking on water

• A restless innovator

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The character

• Radical, bold and defiant

• Protest was preferred to persuasion

• Being right meant it was ok to be rude

• Friends could do no wrong, his enemies could do no right

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His Quest7


I wish to God these calculations had been executed by steam

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Four sources of error

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• Calculation

• Transcription

• Setting of loose type

• Verification


The excitement of the enquiry had an unfavourable effect upon

my bodily health; and I was recommended to abstain entirely for a time from all thought of the

‘Calculating Engine’

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It was certainly fortunate for me, both at this period, and at many times, that I had no sufficiently distinct

view of the multitude of difficulties...which were destined to attend its course. Had these not opened upon me by degrees, I might perhaps never have

ventured on its execution.

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Planning

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• Designs

• Prototypes

• Diversions

• Redesigns


Difference Engine #213


Pioneer of the computer?

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• On switch - crank

• Micro program - stack of cams controlling operation of all parts

• Registers - 7 stacks of 31 rotating digits store and change numbers during calculation

• On screen display - results column

• Printer - prints on paper and stereotype plates

• Fault detection - machine was designed to jam rather than risk delivering an incorrect result


Printer

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• Variable line height

• Variable column width

• Gaps between groups of lines

• 1, 2, 3 or 4 columns

• Stereotypes in 2 font sizes simultaneously and adjusts line height accordingly

• Automatically line wrap or column wrap


Doron Swade

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• Museum curator

• Author

• Specialises in History of Computing

• Authority on Babbage


Difference Engine #2realised

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Authenticity

• Missing information: Methods of manufacturing, tolerance and finish

• Drew knowledge from 19th century machines

• Composition analysis on metals used by Babbage

• Resist the charge “You built the engine, but Babbage could not have”

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Finite Differences

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0 2 -1 4

1 1 3 4

2 4 7 4

3 11 11

4 22

x 2x²-3x+2 Diff 1 Diff 2


No substitute for seeing the machine run

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Questions?

http://panoetic.com@nlisgo

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http://panoetic.com

http://panoetic.com

Technology

Charles Babbage Difference Engine