Atanasoff’s Computer— its impact to the present Information Technology

Tokyo Metropolitan UniversityChikara Fukunaga

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Contents

• Overview of Atanasoff’s computer• Algorithm used in the computer• Logical circuits with vacuum tubes• Performance• Summary• Historical position of the computer

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Atanasoff’s computer• John Vincent Atanasoff and Cliff Berry developed a computing

machine (Atanasoff & Berry Computer; ABC) to solve linear simultaneous algebraic equations with max. 29 unknowns at Iowa State University in 1940

• Although the machine was for the specific purpose, was neither stored-program architecture nor universal, it is regarded now as the origin of the digital (electric) computer. He was regarded as an inventor of it

• We try to clarify the above reasons through this talk

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Джон Винсент Атанасов (1903-1995)

His father was an immigrant from Bulgaria

Principal structure of Atanasoff’s computer

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Synchronization and Control Scheme• Synchronization has been achieved by a purely mechanical way :

electric motor (900rpm) + worm gear (15:1) system

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Atanasoff’s Algorithm• Forward part – elimination of coefficients of x1 to xn one by one

• With max. 28 pairs (for j=2…29), number of unknowns reduced to 28, and 27,26, … finally we get value of Xn

• Backward substitution using the same algorithm used in forward part

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6….. x1

• aij=aik –

(akk/akj)aij is the principle calculation for both forward and backward

• Atanasoff tried to make (akk/akj) with only addition and subtraction

Algorithm 2 update of aij

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akj,j=k..n+1 to Keyboard drumaij,j=k..n+1 to Counter drum

Logical circuit for arithmetic calculation

Atanasoff newly – Introduced logical operation for Arithmetic calculation – devised the following logical table for full adder and subtractor

before the switching theory was born– And realized this logic

in a circuit with vacuum tubes (tri-poles) and resistors network

– Eventually established the base of present digital computer system

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InputAdder Output

Subtractor Output

A B Carry X Carry X Carry

0 0 0 0 0 0 0

0 0 1 1 0 1 1

0 1 0 1 0 1 1

0 1 1 0 1 0 1

1 0 0 1 0 1 0

1 0 1 0 1 0 0

1 1 0 0 1 0 0

1 1 1 1 1 1 1

Truth Table for 1bit full adder/subtractor

Logical circuits with vacuum tubes

• A combination circuit can be constructed with three logical components NOT, NAND and NOR.

• NOT, NAND and NOR can be realized with a resisters network and one tri-pole tube.

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High voltage

ON

~0 V (ground)Low VoltageLow voltage

OFF

~+Vplate

High Voltage

• We can construct the Adder output with combination of NOT,NAND and NOR

• Atanasoff established in this waylogic circuits of full adder/subtractor

Adder output from NOT,NAND and NOR

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InputAdder Output

Subtractor Output

A B Carry X Carry X Carry

0 0 0 0 0 0 0

0 0 1 1 0 1 1

0 1 0 1 0 1 1

0 1 1 0 1 0 1

1 0 0 1 0 1 0

1 0 1 0 1 0 0

1 1 0 0 1 0 0

1 1 1 1 1 1 1

• Computing time estimation fromA.R.Burks and A.W.Burks “The First Electronic Computer: The Atanasoff Story”, 1988, Univ. Michigan

• Anatasoff estimated time=n3/64 hours if we used a table calculator of that time (1940), and it was 380 hours with n=29

Performance

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Summary: What did Atanasoff established

• Digital electric computation– abandoned to use (old fashioned) analogue computers– brought “digital computation” into the calculation machine system

• Electric switching– used a vacuum tube as a simple on/off switch– implemented Boolean logic (truth table) calculation with vacuum tube

circuits• Memory

– Separated memory from arithmetic operation unit (new architecture)– Chose capacitor as the memory element, and refresh system ( DRAM)– developed Rotary drum memory

( magnetic drum, hard disk)• Sequential control system

– Introduced sequential and synchronization concept for machine control04.09.2009

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Historical position of Atanasoff’s computer

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Computer programming

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Programming sequence of a computer program will be expressed as follows ;– It usually consists of

• Sequential operation• Condition Jump (Branch)• Loop (repetition)

For carrying out such a complicated script, we need various hardware components for a computer– Memory (to store program,

variables and constants ）– Arithmetic and Logical Operation Unit– Registers for Arith./Logic Unit and status– Control system

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Follow up 1

Basic hardware structure of a processor

• A typical (simplest) structure will be depicted as

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Follow up 2

von Neumann architecture (1945)

The following conditions are required to be fulfilled in if a machine is regarded as a modern (universal) computer : – Memory access through the address (linear address)– Stored program architecture

• program and data are stored in mix in memory– Program logic dependency

• No distinction between program instructions and data in memory

• Distinction can be made only by the concerned program• If the logic in program is intentionally setup so, the

program can also modify instructions like data– Sequential instruction execution

• A register holds the address of the next instruction to be executed. Instructions are done one by one sequentially

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Follow up 3