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

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 devices

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.