eolas/zk/The_History_of_Computing_Swade.md

title	tags	created
The_History_of_Computing_Swade	literature computer-history	Friday, August 23, 2024

Title	Author	Publication date	Resource type
The History of Computing: A Very Short Introduction	Doron Swade	2022	Book

Timeline

A typical timeline approach rooted in major innovations.

• Ancient aids to counting: knotted cords and notched sticks
• Ancient aids to calculation: counting boards and abacii
• Early mechanical calculator devices in the 17th century (number wheels, Pascal, Leibniz)
• Modern aids to calculation: slide rules following the discovery of logarithms
• Mechanised, automated calculating engines of Babbage in the 19th century
• Punched-card machines leading to IBM in the early 20th century
• Analogue and electro-mechanical computers of the early 20th century inclusive of wartime computers
• Early valve-based (vacuum-tubed) digital computers (again wartime and early Cold War)
• The invention of the transistor and first fully-digital computers
• The invention of integrated_circuits
• Supercomputers
• Minicomputers
• Consumer personal computers
• Internet and later, Web
• Smart phones

First three phases of digital electronic computers:

• Wartime up to 1950s vacuum-tube era
• Transistor era up to 1963
• First microchip era ending in early 1970s

Terms

Term	Definition
automatic	can execute programs, process data and perform functions on its own once it has been started. Can monitor its own processes and make adjustments without human intervention
general-purpose	a computer designed to be able to solve a wide variety of problems and perform many different types of tasks as opposed to a computer built for a specific, limited purpose
programmable	the ability to change the operations a computer peforms without physically altering its hardware

Mechanical calculating devices in the 17th century

Focus was chiefly on creating a desktop calculator capable of four-function arithmetic.

The main contenders were the Pascaline of #Pascal (which only did cumulative addition) and the wheel or "stepped drum" calculator of #Leibniz that could do all operations (in theory).

Subsequent designs were based on these artefacts. In practice, neither worked consistently well with the carriage of tens remaining a sticking point.

The arithmometer (crank driven) and comptometer (key-driven) were descendents of the Leibniz design that became commercially viable by the 19th century along with other mechanical calculators. In the US, Burroughs dominated the market.

Babbage: mechanized, automated calculation

I wish to God these calculations had been executed by Steam (#Babbage)

With Babbage's machines we see an approach to computation that can only be understood against the backdrop of the Industrial Revolution in which they were conceived.

The idea is that the machine is a factory and number is the product. In the same way as the mechanised looms created textiles. It is the extension of a model of industrial production from goods/commodities to information.

Babbage conceived two machines: the Difference Engine (DE) and the Analytical Engine (AE). Neither were successfully built in his lifetime. The DE preceded the AE and was basically an advanced mechanical calculator whereas the AE approximated a general purpose computer.

Despite this, with the Difference Engine, in contrast to preceding aids to calculation, the steps of the computational algorithm were no longer directed by human intelligence but by internal rules embodied in the mechanism and automatically generated.

Difference Engine

The DE's single purpose was to calculate and output mathematical tables such as the results of polynomial equations. The idea was that you would input the variables of the equation and activate the machine and it would output the results. Associated with this concept was the idea that once it arrived at the answer a bell would ring and the machine would halt. This influenced #Turing later. It was non-programmable and designed for a specific set of calculations.

Analytical Engine

Conceived as a general-purpose computing machine capable of perfoming a wide range of calculations, programmable using punched cards similar to those used with Jacquard looms.

It more resembled modern computers in that Babbage used concepts that would later translate into the #vonNeumann architecture. There was a "mill" (CPU), "store" (memory) and input/output mechanisms. It also had a concept of looping and conditional branching.

Lovelace's insight

A central idea of Ada #Lovelace, expressed in her notes on the Analytical Engine is that number can represent entities other than quantity.

If we assign meaning to number, results arrived at by operating on number according to rules can say things about the world when mapped back onto the world using the meanings assigned to them.

Lovelace's insight was that the potential of computing lay in the power of machines to manipulate representations of the world contained in symbols.

Analogue computers

Both digital and analogue computers are automatic. They differ in how they represent quantities and how their outputs are derived.

With digital machines, quantity is represented as a string of discrete digits.

With analogue machines, quantity is a physical property in itself rather than a representation. This could be, for example: the lowering of a weight, the flow of a liquid, or an electrical charge. This physical behaviour is analagous to the system that is being modelled. Quantities are continuously variable values rather than discrete (discontinuous values).

Digital machines produce results by calculation whereas analogue machines produce results by measurement, e.g. the height of liquid in a tank or the time it taks for a tank to be emptied.

Examples of analogue computers

The Phillips Hydraulic Computer

This used fluid to model the workings of the British economy. It consisted of a series of transparent plastic tanks and pipes which were fastened to a wooden board.

Each tank represented some aspect of the UK national economy and the flow of money around the economy was illustrated by coloured water. At the top of the board was a large tank called the treasury. Water (representing money) flowed from the treasury to other tanks representing the various ways in which a country could spend its money. For example, there were tanks for health and education. To increase spending on health care a tap could be opened to drain water from the treasury to the tank which represented health spending.

Bush's Differential Analyser

This was designed to solve differential equations by integration. In contrast to the Philips Computer it was general enough to be used to solve problems from different contexts. Examples of these contexts: heat flow, ballistics, mechanics, population growth, chemical interactions, astronomy.

It was about the size of a room and used shafts, motors, discs and wheels to work.

Historiography

There is a tendency in the history of computing to downplay or diminish the contribution of analogue computing devices and to present them as just an inferior precursor to the inevitable dominance of digital electronic computers.

This is ahistorical and inaccurate.

Analogue (and electromechanical devices) overlapped with and coexisted with digital devices for 40 years, spanning the first three generations of digital electronic devices. The term "analogue" itself only came about when the need arose to distinguish digital devices from other types of computer. They were not "rivals" before this.

Electro-mechanical computers

Electro-mechanical devices (also known as "electronic analogue computers") are a sort of midway between full digital devices and analogue computers, forming a bridge between the two eras.

Their heyday was roughly 1935 - 1945.

Their key components were:

• relays for logic operations
• rotating shafts and gears for performing calculations
• punched cards or paper tape for input instructions and outputs

They were slower than fully digital computers as they were limited by the speed of moving components rather than the flow of electric charge. In addition the various mechanical parts were prone to wear and needed frequent replacement.

Examples of electro-mechanical computers

Harvard Mark 1 (1937-1944) - Aikin, IBM

Designed by Howard Aiken and built by IBM (1937-1944). Also known as the Automatic Sequence Controlled Calculator (ASCC). A general-purpose electro-mechanical computer it was most famously used at Los Alamos by #vonNeumann to calculate the blast yield of the atomic bomb.

It was more than 15m in length and weighed 5 tonnes comprising over 750,000 parts. It used paper tape and punched cards for input/output.

Complex Number Calculator (1940) - Bell Labs, Stibitz

Not general purpose nor was it programmable. It was hardwired to perform a specific set of operations on numbers and nothing else. It used relays like the others. Its distinguishing feature was that it used a teletype for input rather than cards or paper tape.

It comprised a panel (the calculating unit) and teletype (the input). One could remotely access the computer from the teletype in another location, providing it was connected to Bell Lab's telephone network.

Z3 (1941) - Konrad Zuse

First designed in 1938 and completed in 1941. Considered the first fully automatic, programmable digital computer although relay-based. Programs were stored on external punched tape and binary was used as the number system. Destroyed by Allied bombing in the War but a replica (pictured) was built in 1998.

Vacuum-tube devices

Vacuum-tube devices were the first fully electronic digital devices as they used vacuum-tubes for implementing binary logic rather than relay switches.

Canonical examples from this era are the ABC computer, the Collossus and most famously, the ENIAC.

The Antanasoff-Berry Computer (1939 - 1942)

Fully automatic, digital electronic computer but not programmable or really general-purpose, being created to do linear equations. It took decimal input and output but operated internally using binary arithmetic. The input was punched cards and the output was via a front-panel display.

Its importance stems from the fact that it was the first to use vacuum-tubes for the arithmetic calculations of the processor.

Colossus (1943-1945) - Tommy Flowers/Max Newman

Designed and built at the Post Office Research Station at Dollis Hill. Used for cracking the Lorenz messages of the German high command.

Mainly important (beyond its role in the War) for establishing the viability of vacuum-tubes over relays. It comprised 2.4 thousand tubes.

Debatable the extent to which the Collosus can be called the first digital computer since it was not general purpose and not fully programmable.

Furthermore it was not even a complete solution in its context of application. The codebreakers would be given a certain advantage using the Collosus (narrowing the field of possible deciphering keys) but still need to use manual methods to break the code. It made decipher time shorter rather than executing the full diciphering. In contrast to, say, the Bombe computer that would identify the key for the days transmissions.

It's actual influence is also hard to gauge because of the secrecy that remained in place after the War. Apart from those who worked on it, its technical advancements were not public knowledge until the late 1970s.

ENIAC (1945) John Mauchly/J.P Eckert

The Electronic Numerical Calculator and Integrator

The main motivation for creating the ENIAC was military: the US Army needed speed and accuracy when calculating artiliary firing tables and munition trajectory so that shells could hit their intended targets. Accuracy depended on myriad factors: gun elevation, shell shape and weight, explosive charge, distance, wind, temperature etc. Previously this had been done by human computers under the aegis of the Ballistic Research Laboratory.

It was not completed until after VE day but was used at Los Alamos after the War and retired in 1955.

The BRL commissioned the Moore School of Engineering at the University of Pennsylvania for the construction of an automatic electronic calculator.

It used vacuum-tubes, along with switches and realys. It used decimal rather than binary and had punch card input and output. It was crudely programmable and could be set up to work on different problems by rearranging the different components using switches and plugboards. But this took roughly two days.

It's design was very influential because it was made public and not classified.

EDVAC (1944-49) John Mauchly/J.P Eckert/ John von Neumann

Built at the Moore School for the BRL as a successor to ENIAC by Mauchly and Eckert whilst ENIAC was still operational. It's architecture arose out of discussions between #vonNeumann and Mauchly and Eckert and was necessitated by the need to calculate the behaviour of the fissile materials in the atomic bomb.

It resulted in the famous First Draft of a Report on the EDVAC by #vonNeumann which is seen as the definitive statement of the modern digital programmable general-purpose computer.

As a result of the paper, #vonNeumann effectively got the credit for the invention even though it synthesised ideas from the ENIAC and the contributions of others to the EDVAC.

There was lots of disputed provenance and claims of plagiarism generally. Antanasoff won a legal claim against Eckert and Mauchly for stealing ideas from the ABC to make ENIAC.

// Add more on the hardware.

Concept of the internal stored program

• Key innovation of the EDVAC was the internal stored program (ISP).
• Solution to the problem of preceding computers requiring down-time when switching between applications and problem sets.
• Circuitry would need to be reconfigured before the computer could run on the next problem
• ISP removed the friction:
  • the instructions comprising the program would be prepared on tape or punched cards and read into electronic memory
  • the hardware configuration of the machine would remain the same accross different programs and require no reconfiguration, only the input program data would change
• This was basically the invention of software. Both instructions and data shared the same memory space once they were read-in. Before, the data would be stored in memory but the instructions would be read one-by-one from the external storage media.
• Key consequences:
  • flexibility (no need for re-wiring)
  • speed: fetching instructions from memory is quicker than fetching from external storage devicde
  • self-modification: since they were in memory, programs could modify themselves during their execution (e.g. use branching conditions) and treating one program as data for another. This enabled more complex algorithms and also opened the possibility of higher-level languages and compilers
  • simplified architecture: both programs and data in memory
  • generalisation: computers could switch between different tasks simply by loading different programs

Post-EDVAC devices

There were several notable devices which attempted to implement the architecture described in the First Draft using vacuum tubes:

• the Manchester "Baby"
• the Cambridge EDSAC
• Turing's ACE computer

Manchester Baby

• An experimental computer intended to create the von Neumann architecture using Williams_Tube_RAM
• Developed at the Univesity of Manchester and completed in 1948.
• Considered the first electronic stored-program computer and first to contain all the elements of a modern electronic digital computer.

EDSAC

• Electronic Delay Storge Automatic Computer
• Constructed by Maurice Wilkes and others at the Mathematical Laboratory Cambridge University (UK).
• The second digital stored-program computer after the Manchester Baby.
• It used vacuum-tubes for the arithmetical operations in the ALU and mercury delay lines for the RAM.