---
tags: [literature, computer-history]
created: Friday, August 23, 2024
---

# History of Computing (Swade, 2022 )

| 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](Logarithms.md)
- 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](Integrated_circuits.md)
- 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.

![Photograph of Pascaline](../img/pascaline.jpg)

![Photograph of replica of Leibniz stepped drum machine](../img/leibniz-stepped-drum.jpg)

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.

![Photograph of Arithmometer](../img/arithmometer.jpg)

![Photograph of Comptometer](../img/comptometer.png)

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
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 performing 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 [von Neumann architecture](CPU_architecture.md) 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.

![Philips Hydraulic Computer](../img/hydraulic_computer.jpg)

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.

![Differential Analyser](../img/differential_analyser_bush.jpg)

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](Relays.md) 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 von
Neumann to calculate the blast yield of the atomic bomb.

![Harvard Mark One](../img/Harvard_Mark_1.jpg)

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.

![Calculating panel of the CMC](../img/complex-number-calculator-bell-labs.jpg)

![Teletype input of CMC](../img/stibitz-teletype.jpg)

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

![Z3](../img/Zuse-Z3.jpeg)

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)

![ABC Computer](../img/abc-computer.jpg)

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.

![The main control panel of the ENIAC](../img/eniac.jpg)

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.

Its 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 von Neumann 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 von Neumann
which is seen as the definitive statement of the modern **digital programmable
general-purpose computer**.

As a result of the paper, von Neumann 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 for logic operations and a
variety of different electronic methods for memory:

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

#### Manchester Baby (1948)

![The Manchester Baby Computer](../img/manchester_baby.png)

- An experimental computer intended to create the
  [von Neumann architecture](CPU_architecture.md) using
  [Williams_Tube_RAM](Williams_Tube_RAM.md)

- 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 (1949) J.Wilkes et al.

![EDSAC](../img/EDSAC.jpg)

- _Electronic Delay Storge Automatic Computer_

- Constructed by Maurice Wilkes and others at the Mathematical Laboratory of the
  University of Cambridge.

- The second digital stored-program computer after the Manchester Baby.

- It used vacuum-tubes for the arithmetical operations in the ALU and mercury
  [delay line memory](Delay_line_memory.md) for the RAM.

- Designed to be used by relatively non-specialist practitioners from other
  university departments who were expected to program it themselves. To this
  end, a formal programming paradigm was forged for the EDSAC which established
  the following:

  - subroutines as a library of common procedures available to programmers (e.g.
    printing a result, reading input tape, program checking, mathematical
    operations)
  - diagnostics: techniques for verifying program code and its correctness

![Programming Digital Electronic Computer book](../img/programming_a_digital_electronic_computter.jpg)

- The key players wrote the first textbook on programming in 1951: _The
  Preparation of Programs for an Electronic Digital Computer_ (Wilkes, Wheeler,
  and Gill)

#### The Automatic Computing Engine (ACE) (1946) Alan Turing

- Technical design provided by Alan Turing working at the Mathematics Division
  of the National Physical Laboratory. The product of Turing's theoretical work
  in "On Computable Numbers" where he proposes the concept of a
  [Turing_machine](Turing_machines.md) and based on his experience with early
  single-purpose computing devices at Bletchley.

- Due to secrecy over wartime work, it was hard for get Turing to build a fully
  electronic implementation since this would disclose advances made during the
  War. Tommy Flowers was intended to be brought in to build it but again this
  was scuppered over the classification of wartime technology. Had this not been
  the case, it is likely it would've been seen as on par with the EDVAC in its
  design, if not dwarfing it.

- Turing proposed a stored program architecture with high-speed memory. It would
  be more perfomant than the EDVAC as a result.

![The Pilot ACE computer](../img/pilot-ace.jpg)

- Turing's actual design was not implemented as it was thought too ambitious
  given how powerful it would need to be. Instead a smaller prototype was made,
  the Pilot ACE. It used vacuum-tubes for logic, and mercury delay lines for
  memory. Data and memory was input via punched cards.

### Further applications of the EDSAC architecture

### LEO I

- Built by Lyons Tea Company to manage business affairs (payroll, inventory,
  stock management)

- Marked a shift from military and academic contexts for computers to business
  and data management.

### IAS machines

![The MANIAC computer](../img/MANIAC_computer.jpg)

Several machines were built at the Institute for Advanced Study utilising the
"von Neumann" architecture and associated advancements such as vacuum-tubes and
Williams' tubes. There was the original IAS machine (1952) as well as the
JOHNNIAC (1954) and MANIAC (1956).

Although their purpose was military (Los Alamos), their designs were public and
widely studied making them influential outside of academia.

### UNIVAC (1951)

![UNIVAC_computer](../img/univac-1.jpg)

Mauchley and Eckert, who had designed the ENIAC left the Moore School and went
into business: Eckert-Mauchley Computer Corporation. This was bought by
Remington Rand and in subsequent years became the main competitor to IBM.

In this capacity they built the UNIVAC: _Universal Automatic Computer_. It's
name being an embodiment of its nature as a general-purpose, electronic digital
computer.

It used vacuum-tubes for logic and mercury delay lines for memory. It had
multiple means of input/output including: directly via an operator console
(basically a typewriter keyboard), magnetic tape for input and output, along
with punched cards.

![UNIVAC operator console](../img/univac-operator-console.jpeg)

It was the first computer specifically designed to include business and
administrative use. This was underscored by its first client: the US Census
Bureau.

A key event was its succesful prediction of the 1952 general election. It
correctly predicted a landslide for Eisenhower (against expectations). (This was
so unlikely, they actually fudged the data because they thought the machine was
way off.) It was a novelty on the results night but it cemented a certain
concept of the computer in the public imagination - large, room sized machines
with blinking lights.

Swade notes that Eckert and Mauchley effectively launched the US commercial
computer industry with the UNIVAC.

## IBM

- First created in 1911 as a merger of four companies all involved in some
  capacity in business data processing. The most significant of these was the
  Hollerith Tabulating Machine Company who's punched card machines had been used
  in the 1890 census, greatly reducing its collation time

- Named IBM in 1924

- UNIVAC represented the encroachment of computing devices into IBM's market of
  punched-card based data-processing and effectively put IBM on notice.

- To attack the threat IBM brought out three crucial machines: the 701, 702
  and 650.

- IBM's approach to marketing their computers was to emphasise the comfort of
  continuity over the shock of the new represented by the UNIVAC. IBM had
  already captured the business market. Their computers would be more of the
  same, just faster and more powerful than their punched card machines due to
  the electronics. To this end they initially did not call their devices
  'computers'.

- IBM were ultimately totally successful in their pivot to the computing market.
  By 1960 it owned over 70% of the data processing and computer market.

### IBM 701 ("Defense Calculator") (1952)

![Control unit of the IBM 701](../img/ibm-701-control-unit.jpeg)

IBM's first electronic computer. It directly competed with the UNIVAC for
government contracts. It followed the prevailing approach of vaccuum tubes for
logic and had a variety of storage methods: Williams tubes,
[magnetic tape](Magnetic_tape.md) , and magentic drums.

701s were used at Los Alamos and avionics companies. Some were also used to
manage payroll in business contexts.

### IBM 702 ("Tape Processing Machine") (1953)

![Advertisement for the IBM 702](../img/ibm-add.jpeg)

Focused primarily on business applications and targetted at businesses rather
than government contracts. Less powerful than the 701.

### IBM 650 (1953)

![IBM 650](../img/ibm-650.jpg)

Low-cost general purpose machine using magnetic drum memory. Marketed as slower
but more affordable than the 700 range. It was mass-produced unlike the others
which were built for specific customers. It was in fact the first mass-produced
computer in the world. It proved the breakout star in IBMs initial line up and
sometimes called "IBM's Model T".

![IBM_650 console panel](../img/ibm-650-console-panel.jpg)

IBM offerred 650s to univesities at a 60% discount on the condition that the
universities would establish courses in computing. This was shrewd as it meant
that a whole generation of engineers and computer scientists learned on 650s and
would prefer them in their research. It also created a pool of skilled users
that would go on to work at IBM.

Donald Knuth dedicated _The Art of Computer Programming_ to the 650.

It used [magnetic drum memory](./Magnetic_drum_memory.md) along with
vacuum-tubes.

### IBM 1401 (1959)

![IBM 1401](../img/ibm-1401.jpg)

Another IBM mainframe. Transistors replaced vacuum-tubes. Magnetic core storage
replaced magnetic drum storage. It was housed in rectangular light-blue cabinets
and the ubiquity of the 1401 in industry earned IBM the moniker 'Big Blue'.

### IBM System/360 (1964)

![IBM 360](../img/ibm-360.jpg)

Named to suggest all-round compatibility - a family of mainframes designed to
cover commercial and scientific applications. Considered one of history's most
successful computers.

Up until this point all IBM computers had a programming language unique to the
specific processor. At that point there were about seven IBM computer models in
active use and they were all incompatible with each other.

![IBM 360 promo poster](../img/ibm-360-in-use.jpeg)

In contrast the 360 computers all used the same programming language. This meant
they were interoperable with each others. Because the there were variants in the
360 ranges, customers could purchase a smaller system knowing they could expand
it if their needs grew, without reprogramming their application software.

## Magnetic core devices: Whirlwind and SAGE

Two devices that leveraged the new technology of
[magnetic_core_memory](Magnetic_core_memory.md) where the Whirlwind and SAGE
computers. The ENIAC was also updated to use magnetic cores.

![Whirlwind magnetic core memory](../img/whirlwind-magnetic-cores.JPG)

The Whirlwind computer (1953) was a flight simulator and the first to use
magnetic cores. Crucially was able to operate in realtime for output.

The SAGE computer (_Semi-Automatic Ground Environment_) emerged as a response to
the Soviet acquisition of the atomic bomb in 1949. The Americans realised they
needed a much better early warning and air defence system that would allow them
to identify bombers in their airspace and dispatch fighters.

To achieve this, it was necessary to detect enemy bombers with radar and compute
an interception course. Alterations in the bomber flight path required
continuous updates and real-time computation of directions for the responding
fighter.

The resulting computer was SAGE (made by IBM) which was modelled on Whirlwind,
using magnetic cores. SAGE computers were spread accross the continental US in
sectors and managed by NORAD.

![SAGE command post](../img/SAGE_command_post.jpg)

The SAGE system was operation between 1958-1984, receiving continual
improvements and updates. In addition to magnetic cores it introduced many
technological innovations that influenced computers generally: interactive
screens, printed circuit boards, mass-storage devices, digital communication
over telephone lines, time-sharing, along with advances in software.

Because so many private companies worked as contractors on SAGE (IBM, Burroughs,
Bell Labs, RAND Corp), the military technology (both hardware and software) made
its way from the military context to business and consumer computing.

An example of a civilian application of SAGE technology was airline booking
systems, where booking reservation data needed to be processed in realtime. IBM
worked with American Airlines to introduce this.

## Transistor and integrated circuit revolution

The arc of modern computing history (and its main eras) can be presented as

- vacuum-tubes
- [transistors](Transistors.md)
- [integrated_circuits](Integrated_circuits.md)

The transistor was invented at Bell Labs in 1947 by William Shockley and others.
They were not created with computers in mind. Instead they were first used in
hearing aids (1953) and transistor radios (1954).

From the mid-1950s onwards they started being used in military computers.

They had several advantages over vacuum-tubes: they were durable and reliable
with no required startup time, they were power efficient and small.

The actual period where transistors alone were supreme in the form of a
transistor board was relatively short-lived and rapidly gave way to ICs.

Computers of the transistor era had the following components separate from each
other: the transistors, wired connections, resistors and capacitors. Integrated
circuits put these all on the same piece of silicon.

They were first manufactured by Fairchild Semiconductor which was an offshoot of
Shockley's Shockley Semiconductor Laboratory.

The initial marked for ICs was military and scientific: the Minuteman ICBM and
computers of the Apollo spacecraft. This laid the groundworkd for later
commercial use and the personal computer revolution.

## Mini-computers

Mini computers did not threaten mainframes but they opened up a new class of
user. They were vastly cheaper than a mainframe and only the size of a small
fridge.

The main player was DEC (Digital Equipment Corporation) starting in the
mid-1960s. The introduced the PDP-8 in 1965 (Programmed Data Processor). The
PDP-8 used transisotrs and magnetic core memory. It was affordable to smaller
businesses if not yet, consumers.

![The PDP-8](<../img/540px-PDP-8_(1).jpg>)

The internals were made public and DEC encouraged making the machine extensible
by users being permitted to create their own programs and specialised
applications. This was a very different culture to IBM where technicians were
required and machines were typically leased.

By 1988, DEC was the second largest computer company after IBM. This led to
additional companies entering the mini-computer market: Data General, Honeywell,
Hewlett-Packard.

Mini-computers died as a category in the mid-1990s in the wake of the PC.

## The Personal Computer

The PC emerged out of advances in IC chip design - this was the engine of the
PC.

Intel (newly founded by Robert Noyce and Gordon Moore) were charged with making
custom chips for a Japanese calculator company. Instead of creating the custom
chips, they advised the company to use a general purpose chip that could handle
general computing as well as the basic calculator functions. This generic chip -
the Intel 4004 - was the microprocessor combined with three other ICs
(comprising 2.3k transistors) that comprised the fundamental building blocks of
the von Neumann architecture.

![Intel 4004 chip](../img/intel-4004.jpg)

However it took until the Apple II in 1977 for the phrase "personal computer" to
enter the lexicon and become an identifiable class.

The broader context for this was the computer hobbyists in Silicon Valley/Menlo
Park (particularly the Homebrew Club of amateur computer engineers) along with
idealistic figures from the 60s counterculture (such as Stuart Brand) who began
associating computing technology as a tool of personal liberty and fulfillment.

### Microsoft and Apple

The PC "boom" began with the Altair 8800. This was a mail-order kit that
required manual assembly. It was released by Micro Instrumentation Telemetry
Systems (MITS) in 1975. It couldn't do much but had expansion capability
(memory, teletype interface, casette player for data storage).

![Altair 8800](../img/altair-8800.jpg)

Bill Gates and Paul Allen made a proposal to MITS: they would write software
that would allow users to program the Altair in BASIC. They agreed and were
prepared to distribute the software. As a result Gates and Allen founded
Microsoft in 1975.

Around the same time, Steve Wozniak (member of the Homebrew club) built the
Apple I as a single-board hobbyist project. He made this available to buy via
mail order and formed Apple with Steve Jobs in 1976 to manage the enterprise.

![Apple I](../img/apple1.jpg)

By 1977 they had investment capital and brought out the Apple II. This was sold
preassembled with casing and required no soldering. It had expansion slots for
third-party vendors to create compatible devices and had colour graphics.

The design of the Apple II was published in _Byte_ in order to invite
crowd-sourced plugins and extensions. One of these was the Z-80 softcard which
allowed it to run the CP/M OS (created by the company Digital Research) giving
ready-made access to software such as a word-processor, spreadsheets and
databases.

![Apple 2](../img/apple2.jpg)

Other competitors in the PC market at this time were Radioshack's TRS-80 and the
Commodore PET.

### IBM

All the while it was hobbyist and tinkerers driving the PC market, IBM had no
real interest. When PCSs started being used by businesses and their capacity
grew to include typical business applications (databases, spreadsheets) it
sensed an incursion into its market.

![IBM PC](../img/ibm-pc.jpg)

Thus, in 1981, IBM launched the "IBM Personal Computer" which rapidly became the
industry standard. This had the effect of legitimising the concept of a PC.
There was overwhelming demand. In their marketing IBM melded home and office use
to capture both markets at once.

The internal specification of the IBM PC was freely available (dubbed 'open
architecture'), in contrast to IBM's business computers, to encourage software
expansion. Cards could be created to fit in its expansion slots adding graphics,
sound, additional memory and networking capability.

IBM originally contracted Digital Research to create software based on CP/M but
this fell through. Microsoft got the deal to supply the OS which became MS-DOS
(Microsoft Disk Operating System). Henceforth every PC and PC-clone came with
DOS bundled.
