Computer Technology Limited (CTL) was a British computer company founded in 1965. In 1984 it merged into its holding company and was called Information Technology Limited (ITL).
Founder
Iann Barron
Iann Marchant Barron (16 June 1936 ā 16 May 2022) was a British computer engineer and entrepreneur.
During vacation work in 1956ā67 at Elliott Brothers while still at Cambridge he designed the Elliott 803. On leaving University he joine ...
had worked for
Elliott Automation
Elliott Brothers (London) Ltd was an early computer company of the 1950sā60s in the United Kingdom. It traced its descent from a firm of instrument makers founded by William Elliott (instrument maker), William Elliott (1780 or 1781-1853) in ...
but left to form CTL when he couldn't persuade Elliott to incorporate his ideas in their next generation of computers. CTL was financed by the
American Research and Development Corporation
American Research and Development Corporation (ARDC) was a venture capital and private equity firm founded in 1946 by Georges Doriot, Ralph Flanders, Merrill Griswold, and Karl Compton.
ARDC is credited with the first major venture capital su ...
and
Pergamon Press
Pergamon Press was an Oxford-based publishing house, founded by Paul Rosbaud and Robert Maxwell, that published scientific and medical books and journals. Originally called Butterworth-Springer, it is now an imprint of Elsevier.
History
The cor ...
.
The first CTL computer, the Modular One, appeared for sale in 1968.
Modular One
The Modular One was a 16-bit computer built with
Emitter Coupled Logic
In electronics, emitter-coupled logic (ECL) is a high-speed integrated circuit bipolar transistor logic family. ECL uses an overdriven bipolar junction transistor (BJT) differential amplifier with single-ended input and limited emitter current to ...
(ECL) and was competitive with other first generation
minicomputers
A minicomputer, or colloquially mini, is a class of smaller general purpose computers that developed in the mid-1960s and sold at a much lower price than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, ...
.
Features
A key feature, from which it derived its name, was that it was composed of separate processor, memory and peripheral modules sharing a common interface and physical form factor, so allowing them to be put together in any combination, housed one or two high in modular racking. Standard modules were roughly 50 cm wide and deep, 70 cm tall, and complete with power supply, typically weighed in excess of 25 kg. Modules were interconnected using a single type of interface, comprising two identical cards to be plugged into two modules to be connected, these cards themselves linked by a flat ribbon cable either one or two metres long. Thus, memory was just another peripheral (such as a printer) but was both input and output.
Every interaction over these interfaces comprised a 3-way handshake, which in the case of a processor accessing a memory module, consisted of send address, receive data, and send new data, a scheme well suited to the destructive read followed by rewrite required by
magnetic-core memory
Magnetic-core memory was the predominant form of random access, random-access computer memory for 20 years between about 1955 and 1975.
Such memory is often just called core memory, or, informally, core.
Core memory uses toroids (rings) of a ...
of the time. These three phases were mediated by voltage edges rather than pulses, as this was thought to be faster. Furthermore, the input and output impedances of ECL were comparable to the characteristic impedance of ribbon cable. This, together with the small voltage swings between the "0" and "1" states made for low noise, reflection-free communication.
Processors naturally had a number of interface slots bussed together, allowing connection to memory and peripheral modules as required. Memory modules had several, allowing them to be accessed by more than one processor as well as by disc controllers for DMA. Disc controllers could be connected to two processors as well as memory modules. All modules had a "1.x" type designation, for example, the original processor module was 1.11, memory modules were 1.2x, character peripherals were 1.3x, discs were 1.4x and magnetic tape devices were 1.5x. The standard interface was designated 1.01.
The various building blocks could be assembled and configured to produce a
fault-tolerant computer system
Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the ...
.
Distinctive features of the processor were memory-mapped I/O and an early version of segmented memory (similar to the later
Intel 8086
The 8086 (also called iAPX 86) is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus (allowi ...
but having both base and limit). The processor had 3 segment registers referred to as X, Y and Z. The X segment was read/execute only and used to map code segments (corresponding to CS in the x86 architecture). It was not possible to execute code in the Y and Z segments, which were used for data (roughly corresponding to DS and ES in x86). There were 8 addressing modes allowing access to data mapped by the segment registers in various ways.
The memory segmentation, together with two execution states (
Normal State and non-interruptible privileged
Special State) made possible the implementation of a self-protecting operating system kernel (known as the Executive, or Exec). Such ideas were popular in British computer academia at the time and later were adopted by some US designs such as the
Motorola 68000
The Motorola 68000 (sometimes shortened to Motorola 68k or m68k and usually pronounced "sixty-eight-thousand") is a 16/32-bit complex instruction set computer (CISC) microprocessor, introduced in 1979 by Motorola Semiconductor Products Sector ...
and
Intel 80286
The Intel 80286 (also marketed as the iAPX 286 and often called Intel 286) is a 16-bit microprocessor that was introduced on February 1, 1982. It was the first 8086-based CPU with separate, non-multiplexed address and data buses and also the fi ...
. Furthermore, the power system was set up as a peripheral with interrupt capabilities that gave the machine the ability to power down gracefully in an emergency.
Sales history
The Modular One was comparatively expensive. It was somewhat exotic in that its modular design resulted in almost every system delivered being somewhat different, which created a high maintenance burden.
Many universities were equipped with Modular One systems, in part due to the government of the time having a 'buy British' policy. Acting as a front-end processor for the
ICL 1900
ICT 1900 was a family of mainframe computers released by International Computers and Tabulators (ICT) and later International Computers Limited (ICL) during the 1960s and 1970s. The 1900 series was notable for being one of the few non-American ...
mainframe, driving multiple online terminals or as a remote batch job entry station, was a major market for the Modular One.
[
It never sold widely outside of the UK, and even in the UK it was surpassed in sales by ]Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...
(DEC) and Data General
Data General Corporation was one of the first minicomputer firms of the late 1960s. Three of the four founders were former employees of Digital Equipment Corporation (DEC).
Their first product, 1969's Data General Nova, was a 16-bit minicomputer ...
before the end of the 1970s.[
Over the mid 1970s to mid 1980s the systems were cost reduced with TTL bitslice technology and 8-bit microprocessor communications controllers, retreating from the radical modular design, but it never gained a significant market share.
]
Legacy
Very few Modular One computers now remain, possibly only the example being that restored by Redhawk Systems Ltd.
Operating system
The operating system kernel was referred to as the Exec. Several simple ones (E1, E2 and E3) were developed in the early years of the company. E4, first in-house release around 1973, written entirely in assembler
Assembler may refer to:
Arts and media
* Nobukazu Takemura, avant-garde electronic musician, stage name Assembler
* Assemblers, a fictional race in the ''Star Wars'' universe
* Assemblers, an alternative name of the superhero group Champions of A ...
, was a multitasking kernel using Dijkstra semaphores to protect internal data structures from conflicts. It was based on an early version of object-oriented
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of pro ...
principles, though lacking most of what are now considered essential features of the paradigm, such as inheritance.
Objects included Activities (now more commonly known as tasks or processes), Segments (of memory), Files, Semaphores and Clocks. Another object type, the Sphere, was a run-time protection domain within which all other object types (including other Spheres) existed. Objects could be created in arbitrary quantities, and were each referenced through a Run Time Name, or RTN. Since an object could be referenced by several RTNs belonging to different spheres, they could easily be shared between programs, and were deleted only when the object's reference count of RTNs fell to zero. Linked lists were used very extensively within E4 to manage data structures, in fact the RTN list was about the only linear list there was. (The system generation process included a phase prosaically called "knitting" comprising a combination of macro expansion and procedural elements, by which the initial data structures were dynamically "knitted" together to create an input file for the assembler.)
The ease with which multiple processor, store and peripheral modules could be built into a system, plus the need to extend the upper capability limits, prompted the development of a dual processor variant of E4. This was built entirely from standard modules except for a small synchronisation board which prevented both processors operating simultaneously in special state, and a very minor modification to one of the processors' interface to store zero, allowing each processor to address a small dedicated memory area for processor-specific variables such as the current activity. However, the results were somewhat disappointing as E4 naturally spent a significant proportion of its time in special state even though efforts had always made to limit special state routines to 100uS at a time. Even running processor-bound user programs, the performance achieved was only of the order of 150% of that of a single processor, and no dual processor E4 systems were ever sold.
There was some similarity to Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
in the use of (mainly) device-independent serial byte oriented streams in the file system and interprocess communication, in contrast to the record-oriented file systems then dominant in commercial data processing. E4 also supported real-time priorities and virtual memory at the Segment level.
E4 had a primitive command line interface but a multi-access operating system known as Modus was built on top of it for much greater flexibility and ease of use. This consisted of a "Nucleus" which looked after a collection of "Engines". An Engine was typically associated with a peripheral device and processed work from a queue, for example taking print jobs from a print queue and printing them. A special case was the Read Engine, which was the command processor. This was either associated with a terminal device (in which case it had a terminal device but no queue), or was a batch processor (in which case it had a queue but no device).
The filing system, SDFS, was not part of the kernel but was a separate program. A multi-key indexed file system MKFS was also developed, and together with a transaction processing system and a report generator, formed the basis of many sales into commercial applications.
Modus and many of the applications were written in the high level language Coral 66
Corals are marine invertebrates within the class (biology), class Anthozoa of the phylum Cnidaria. They typically form compact Colony (biology), colonies of many identical individual polyp (zoology), polyps. Coral species include the important C ...
. Compilers for COBOL
COBOL (; an acronym for "common business-oriented language") is a compiled English-like computer programming language designed for business use. It is an imperative, procedural and, since 2002, object-oriented language. COBOL is primarily us ...
and FORTRAN IV were also available for the Modular One.
Later history
Founder Iann Barron left in 1971, following the collapse of a major customer. He went on to form Inmos and develop the transputer
The transputer is a series of pioneering microprocessors from the 1980s, intended for parallel computing. To support this, each transputer had its own integrated memory and serial communication links to exchange data with other transputers. T ...
. He was replaced as Chairman by Tom Margerison, from London Weekend Television
London Weekend Television (LWT) (now part of the non-franchised ITV London region) was the ITV network franchise holder for Greater London and the Home Counties at weekends, broadcasting from Fridays at 5.15 pm (7:00 pm from 1968 unt ...
.[
During the 1970s CTL operated modestly successfully in a number of niche markets, while larger American competitors, such as ]Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president unt ...
(DEC) with their PDP range, increased market share. In 1980 two sibling companies Office Technology Limited (OTL) and Network Technology Limited (NTL), and a holding company Information Technology Limited (ITL) were created.[
In 1981 entrepreneur Tony Davies became Managing Director. Under Davies CTL began buying in hardware, to be re-badged as CTL systems, recognising CTL could not afford to develop hardware at all levels. The first was a ]Convergent Technologies
Convergent Technologies was an American computer company formed by a small group of people who left Intel Corporation and Xerox PARC in 1979. Among the founders were CEO Allen Michels, VP Engineering Bob Garrow, head of marketing Kal Hubler, and ...
8086 system which created a price competitive small system for CTL. In 1984 all the subsidiaries were merged into the holding company Information Technology Limited (ITL), replacing the CTL name. Nominally this was an efficiency measure, but it also positioned the company better for a possible public offering on the stock markets.[
During the mid 1980s, the company decided that the future lay in open systems and CTL attempted to make the transition to ]Unix
Unix (; trademarked as UNIX) is a family of multitasking, multiuser computer operating systems that derive from the original AT&T Unix, whose development started in 1969 at the Bell Labs research center by Ken Thompson, Dennis Ritchie, and ot ...
with re-badged systems from Motorola
Motorola, Inc. () was an American Multinational corporation, multinational telecommunications company based in Schaumburg, Illinois, United States. After having lost $4.3 billion from 2007 to 2009, the company split into two independent p ...
and Sequoia Systems. However, sales of CTL's proprietary systems fell off before the new systems could be ramped up to replace them.
The company was taken over by ACT in 1989, primarily for its customers and extensive support network, which effectively ended CTL's era as a computer manufacturer.[
]
Headquarters
In 1969, Computer Technology hired then up-and-coming architect Norman Foster
Norman or Normans may refer to:
Ethnic and cultural identity
* The Normans, a people partly descended from Norse Vikings who settled in the territory of Normandy in France in the 10th and 11th centuries
** People or things connected with the Norm ...
to design their new headquarters north of London, in Hemel Hempstead
Hemel Hempstead () is a town in the Dacorum district in Hertfordshire, England, northwest of London, which is part of the Greater London Urban Area. The population at the 2011 census was 97,500.
Developed after the Second World War as a ne ...
. Foster responded to the company's need for an open office plan, as well as a compressed building schedule, by designing an innovative inflatable structure or "air tent" that was critically lauded by the architectural press at the time of its unveiling.
See also
* Digico Limited
The Company name 'Computer Technology Limited' is currently registered and in use by: https://www.computer-technology.co.uk/
References
{{Reflist, 30em
1965 establishments in England
Companies based in Hertfordshire
Computer companies established in 1965
Defunct computer companies of the United Kingdom
Minicomputers