The APE(X)C, or All Purpose Electronic (X) Computer series was designed by
at
Birkbeck College
Birkbeck, University of London (formally Birkbeck College, University of London), is a public university, public research university, located in Bloomsbury, London, England, and a constituent college, member institution of the federal Universit ...
,
London
London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...
in the early 1950s. His work on the APE(X)C series was sponsored by the
British Rayon Research Association
The British Rayon Research Association was a research institute formed in 1946 by the British Rayon Federation and others.The Times, November 29, 1946 page 10 It was funded by the Department of Scientific and Industrial Research and by voluntary fu ...
.
[Early British computers, Simon Hugh Lavington 1980] Although the naming conventions are slightly unclear, it seems the first model belonged to the BRRA.
[History of Computing:Learning from the Past, Arthur Tatnall Springer, 2010] According to Booth, the X stood for X-company.
One of the series was also known as the APE(X)C or All Purpose Electronic X-Ray Computer and was sited at Birkbeck.
Background
From 1943 on, Booth started working on the determination of
crystal
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...
structures using
X-ray diffraction
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...
data. The computations involved were extremely tedious and there was ample incentive for automating the process and he developed an analogue computer to compute the reciprocal spacings of the diffraction pattern.
In 1947, along with his collaborator and future spouse
Kathleen Britten, he spent a few months with
von Neumann Von Neumann may refer to:
* John von Neumann (1903–1957), a Hungarian American mathematician
* Von Neumann family
* Von Neumann (surname), a German surname
* Von Neumann (crater), a lunar impact crater
See also
* Von Neumann algebra
* Von Ne ...
's team, which was the leading edge in computer research at the time.
ARC and SEC
Booth designed an electromechanical computer, the
ARC
ARC may refer to:
Business
* Aircraft Radio Corporation, a major avionics manufacturer from the 1920s to the '50s
* Airlines Reporting Corporation, an airline-owned company that provides ticket distribution, reporting, and settlement services
* ...
(Automatic Relay Computer), in the late 1940s (1947-1948). Later on, they built an experimental electronic computer named SEC (
Simple Electronic Computer, designed around 1948-1949) - and finally, the APE(X)C (All-Purpose Electronic Computer) series.
The computers were programmed by Kathleen.
The APE(X) C series
The APE(X)C series included the following machines:
* APE(X)C: Birkbeck College, London, first time operated in May 1952,
ready for use at the end of 1953
* APE(N)C:
Board of Mathematical Machines,
Oslo
Oslo ( , , or ; sma, Oslove) is the capital and most populous city of Norway. It constitutes both a county and a municipality. The municipality of Oslo had a population of in 2022, while the city's greater urban area had a population of ...
('N' likely stands for '
Norway
Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and t ...
'), also known as
NUSSE
* APE(H)C:
British Tabulating Machine Company
__NOTOC__
The British Tabulating Machine Company (BTM) was a firm which manufactured and sold Hollerith unit record equipment and other data-processing equipment. During World War II, BTM constructed some 200 "bombes", machines used at Bletchley P ...
(It is unclear what 'H' stands for - perhaps '
Hollerith
Herman Hollerith (February 29, 1860 – November 17, 1929) was a German-American statistician, inventor, and businessman who developed an electromechanical tabulating machine for punched cards to assist in summarizing information and, later, in ...
' as the company sold Hollerith
Unit record equipment
Starting at the end of the nineteenth century, well before the advent of electronic computers, data processing was performed using electromechanical machines collectively referred to as unit record equipment, electric accounting machines (EAM) o ...
* APE(R)C:
British Rayon Research Association
The British Rayon Research Association was a research institute formed in 1946 by the British Rayon Federation and others.The Times, November 29, 1946 page 10 It was funded by the Department of Scientific and Industrial Research and by voluntary fu ...
('R' stands for 'Rayon'
), ready for use in June 1952
* UCC:
University College, London
, mottoeng = Let all come who by merit deserve the most reward
, established =
, type = Public research university
, endowment = £143 million (2020)
, budget = Â ...
(circa January 1956)
* MAC or MAGIC (Magnetic Automatic Calculator): "built by
Wharf Engineering Laboratories
A wharf, quay (, also ), staith, or staithe is a structure on the shore of a harbour or on the bank of a river or canal where ships may dock to load and unload cargo or passengers. Such a structure includes one or more berths (mooring locatio ...
" (February 1955)
* The HEC (
Hollerith Electronic Computer
The Hollerith Electronic Computer (HEC) was produced by the British Tabulating Machine Company (BTM) and was based on a design by Professor Andrew Booth of Birkbeck College, London. It was Britain's first mass-produced business computer. The pro ...
), built by the British Tabulating Machine Company (later to become
International Computers and Tabulators
International Computers and Tabulators or ICT was a British computer manufacturer, formed in 1959 by a merger of the British Tabulating Machine Company (BTM) and Powers-Samas. In 1963 it acquired the business computer divisions of Ferranti. It ...
(ICT), then
International Computers Limited
International Computers Limited (ICL) was a British computer hardware, computer software and computer services company that operated from 1968 until 2002. It was formed through a merger of International Computers and Tabulators (ICT), English Ele ...
(ICL)), a commercial machine sold in several models and later known as the ICT200 series. There were likely the derivatives HEC 1, HEC 2, HEC 2M - M for 'marketable' denoting the machine's orientation toward commercial rather than scientific customers, and HEC 4 (before 1955)
Only one of each of these machines was built, with the exception of HEC (and possibly MAC) which were commercial machines produced in quite large numbers for the time, around 150. They were similar in design, with various small differences, mostly in I/O equipment. The APEHC was a
punched card
A punched card (also punch card or punched-card) is a piece of stiff paper that holds digital data represented by the presence or absence of holes in predefined positions. Punched cards were once common in data processing applications or to di ...
machine while the APEXC, APERC and APENC were
teletype
A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initia ...
rs (
keyboard
Keyboard may refer to:
Text input
* Keyboard, part of a typewriter
* Computer keyboard
** Keyboard layout, the software control of computer keyboards and their mapping
** Keyboard technology, computer keyboard hardware and firmware
Music
* Musi ...
and
printer
Printer may refer to:
Technology
* Printer (publishing), a person or a company
* Printer (computing), a hardware device
* Optical printer for motion picture films
People
* Nariman Printer ( fl. c. 1940), Indian journalist and activist
* Jame ...
, plus
paper tape
Five- and eight-hole punched paper tape
Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop
Punched tape or perforated paper tape is a form of data storage ...
reader and puncher). Also, the UCC had 8k words of storage, instead of 1k word for other machines, and the MAC used germanium diodes in replacement of many valves.
British Tabulating Machine Company machines
In March 1951, the British Tabulating Machine Company (BTM) sent a team to Andrew Booth's workshop. They then used his design to create the Hollerith Electronic Computer 1 (HEC 1) before the end of 1951. The computer was a direct copy of Andrew Booth's circuits with extra Input/output interfaces. The HEC 2 was the HEC 1 with smarter metal casings and was built for the
Business Efficiency Exhibition
Business is the practice of making one's living or making money by producing or buying and selling products (such as goods and services). It is also "any activity or enterprise entered into for profit."
Having a business name does not separate ...
in 1953. A slightly modified version of the HEC 2 was then marketed as HEC2M and 8 were sold. The HEC2M was succeeded by the HEC4. Around 100 HEC4s were sold in the late 1950s.
The HEC used standard
punched cards
A punched card (also punch card or punched-card) is a piece of stiff paper that holds digital data represented by the presence or absence of holes in predefined positions. Punched cards were once common in data processing applications or to d ...
; the HEC 4 had a printer, too, and it featured several instructions (such as
divide) and registers not found on the APEXC.
Technical description
An emulator for the APEXC series has been developed by
MESS
The mess (also called a mess deck aboard ships) is a designated area where military personnel socialize, eat and (in some cases) live. The term is also used to indicate the groups of military personnel who belong to separate messes, such as the o ...
. They describe its functioning as follows:
The APEXC is an incredibly simple machine.
Instruction and data words are always 32 bits long. The processor uses integer arithmetic with 2's complement representation. Addresses are 10 bits long. The APEXC has no RAM
Ram, ram, or RAM may refer to:
Animals
* A male sheep
* Ram cichlid, a freshwater tropical fish
People
* Ram (given name)
* Ram (surname)
* Ram (director) (Ramsubramaniam), an Indian Tamil film director
* RAM (musician) (born 1974), Dutch
* Ra ...
, except for a 32-bit accumulator and a 32-bit data register (used along with the 32-bit accumulator to implement 64-bit shift instructions and hold the 64-bit result of a multiplication
Multiplication (often denoted by the cross symbol , by the mid-line dot operator , by juxtaposition, or, on computers, by an asterisk ) is one of the four elementary mathematical operations of arithmetic, with the other ones being additi ...
). Instructions and data are stored in two magnetic drum
Drum memory was a magnetic data storage device invented by Gustav Tauschek in 1932 in Austria. Drums were widely used in the 1950s and into the 1960s as computer memory.
For many early computers, drum memory formed the main working memory ...
s, for a total of 32 circular magnetic tracks of 32 words. Since the rotation rate is 3750rpm
Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines.
Standards
ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
(62.5 rotations per second), the program execution speed can go from as high as the theoretical maximum of 1 kIPS to lower than 100IPS if program instructions and data are not contiguous. Nowadays, many say a pocket calculator
An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics.
The first solid-state electronic calculator was created in the early 1960s. Pocket-sized ...
is faster.
One oddity is that there is no program counter
The program counter (PC), commonly called the instruction pointer (IP) in Intel x86 and Itanium microprocessors, and sometimes called the instruction address register (IAR), the instruction counter, or just part of the instruction sequencer, is ...
: each machine instruction includes the address of the next instruction. This design may sound weird, but it is the only way to achieve optimal performance with this cylinder-based memory.
The machine code is made of 15 instructions only, namely addition
Addition (usually signified by the Plus and minus signs#Plus sign, plus symbol ) is one of the four basic Operation (mathematics), operations of arithmetic, the other three being subtraction, multiplication and Division (mathematics), division. ...
, subtraction
Subtraction is an arithmetic operation that represents the operation of removing objects from a collection. Subtraction is signified by the minus sign, . For example, in the adjacent picture, there are peaches—meaning 5 peaches with 2 taken ...
, multiplication, load (3 variants), store (2 variants), conditional branch
A branch is an instruction in a computer program that can cause a computer to begin executing a different instruction sequence and thus deviate from its default behavior of executing instructions in order. ''Branch'' (or ''branching'', ''branc ...
, right arithmetic bit shift, right bit rotation, punched-card input, punched-card output, machine stop, and bank-switching (which is never used on the APEXC, since it only has 1024 words of storage, and addresses are 10-bit-long). A so-called vector mode enables to repeat the same operation 32 times with 32 successive memory locations. Note the lack of bitwise and/or/xor and division. Also, note the lack of indirect addressing modes: dynamic modification of opcodes is the only way one may simulate it.
Another oddity is that the memory bus and the ALU are 1-bit-wide. There is a 64 kHz
The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that on ...
bit-clock and a 2 kHz word-clock, and each word memory and arithmetic operation is decomposed into 32 1-bit memory and arithmetic operations: this takes 32 bit cycles, for a total of 1 word cycle.
The processor is fairly efficient: most instructions take only 2 word cycles (1 for fetch, 1 for read operand and execute), with the exception of stores, shifts and multiplications. The APEXC CPU qualifies as RISC
In computer engineering, a reduced instruction set computer (RISC) is a computer designed to simplify the individual instructions given to the computer to accomplish tasks. Compared to the instructions given to a complex instruction set comput ...
; there is no other adequate word.
Note there is no read-only memory
Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing sof ...
(ROM), and therefore no bootstrap loader
In computing, booting is the process of starting a computer as initiated via hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its main memory, so some ...
or default start-up program whatsoever. It is believed that no executive or operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs.
Time-sharing operating systems schedule tasks for efficient use of the system and may also in ...
was ever written for the APEXC, although there were subroutine
In computer programming, a function or subroutine is a sequence of program instructions that performs a specific task, packaged as a unit. This unit can then be used in programs wherever that particular task should be performed.
Functions may ...
libraries
A library is a collection of materials, books or media that are accessible for use and not just for display purposes. A library provides physical (hard copies) or digital access (soft copies) materials, and may be a physical location or a vir ...
of sorts for common arithmetic, I/O and debug tasks.
Operation of the machine is normally done through a control panel which allows the user to start, stop and resume the central processing unit
A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, an ...
, and to alter registers and memory when the CPU is stopped. When starting the machine, the address
An address is a collection of information, presented in a mostly fixed format, used to give the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along w ...
of the first instruction of the program to be executed must be entered in the control panel, then the run switch must be pressed. Most programs end with a stop instruction, which enables the operator to check the state of the machine, possibly run some post-mortem debugging procedures (a core dump
In computing, a core dump, memory dump, crash dump, storage dump, system dump, or ABEND dump consists of the recorded state of the working memory of a computer program at a specific time, generally when the program has crashed or otherwise terminat ...
routine is described in an APEXC programming book), then enter the address of another program and run it.
Two I/O devices were supported: a paper tape reader, and a paper tape puncher. The puncher output could be fed to a printer ('teletyper') unit when desirable. Printer output is emulated and is displayed on screen. Tape input was either computer-generated by the APEXC, or hand-typed with a special 32-key keyboard (each tape row had 5 data holes (<-> bits), which makes 32 different values).[http://mess.redump.net/sysinfo:apexc Multi Emulator Super System technical description of the APEXC series]
Further reading
* Andrew D. Booth Technical Developments: The Development of A.P.E.(X).C. (i
Automatic Computing Machinery, Mathematical Tables and Other Aids to Computation (MTAC) Volume 8, Number 46, April, 1954
References
{{reflist
1940s computers
1950s computers
Computer-related introductions in 1948
Crystallography
Early British computers
One-of-a-kind computers