1.2 - The ICT 1900 Range in 1966


After the introduction of 1901, the first manifestation of the 1900 Range was complete. The following is an extract from an ICT brochure (Nov. ’66), describing the full range and emphasizing what, at the time, was considered important and innovative in the ICT 1900.


I.C.T. has designed the 1900 Series from the beginning as a complete series of systems, in which all central processors and peripherals are of one family and all equipment, programs and data representation are compatible. All necessary facilities both for commercial and scientific applications are incorporated. In scope the Series extends from a configuration priced as low as £28,000 to one of £750,000 or more. This is what it offers to every user:

Freedom of Choice The 1900 Series has an extensive range of compatible processors and peripherals, enabling the user to choose the initial configuration best suited both to the volume and to the type of work that he is ready to load onto the system now. He can start economically, without overspending either in terms of manpower or money.

Freedom to Expand The 1900 Series thrives on growth both in volume of work and in scope of operations in any application. It grows with the user as he grows. It provides additional facilities as he needs them. Whether the requirement is on site or far afield, the communications facilities of the equipment permit virtually unlimited expansion. The 1900 Series is designed round the concept of Standard Interface, through which standardized sets of signals transfer information between all processors and all peripheral devices. All components thus become fully interchangeable. Complete flexibility is provided throughout the system, and new peripheral devices can be attached to an existing processor. Conversely, if and when more work capacity is required more core storage can be added or a more powerful central processor can be substituted, the existing peripheral units being retained. Processors communicate with each other and with the peripherals of their own and other systems. Expansion through the linking of a network of individual systems is therefore made possible.

A Single Programming Investment The I.C.T. 1900 Series is simple to program because it has been designed around comprehensive and simple programming languages, which are common to every processor in the series. The original investment in programming is not lost as the user expands his 1900 Series installation, and indeed will not be lost whatever developments take place within the I.C.T. range of computing systems.

Simplicity in Operation Communication with the 1900 Series is simple. A typewriter passes instructions to the computer system in plain language and from there "Executive" —the Master Program—takes over. "Executive" is a special program provided by I.C.T. which supervises the operation of the system for the user. It reports upon the progress of programs and the state of peripheral devices, controls the transfer of information and generally oversees the functions of each component device in the system. It also continuously monitors performance, to ensure accuracy and to avoid any possibility of error.

Vast Variety and Capacity of Storage The I.C.T. 1900 Series provides data storage devices from magnetic drums, through exchangeable disc stores to the largest scale file storage devices, such as the magnetic card file. These provide immediate access at a cost lower than comparable systems. The user can therefore choose from a selection of random access devices in the area of cost appropriate to his work, and open the door to a new approach in management techniques.



Detailed specification

This section shows the full scope of the choice in central processors, input and output peripherals, storage, display devices and communications available now.

Central Processors

All central processors may be specified; all designed to obey the same instruction code so that programs written for the smallest machine can be processed by any in the series. All the processors are expansible on site and can be replaced by a more powerful processor. This is possible because all peripheral devices—input, output, storage and communications—are attached to the processor via I.C.T. Standard Interface.

Instruction Code

The instruction code, common to all machines in the series, is extremely powerful and very comprehensive. Functions which are performed by circuits in the faster processors are called by "Extracodes" in the simpler versions.

Standard Interface

This feature makes it possible to connect peripherals of different functions and speeds to the central processor, handling transfers to and from the peripheral to which it is connected. Devices of the future will also be linked to the processor by this means.


1901 Processor: The smallest in the range, this processor is designed to provide a new low-cost data processing system that is suitable for the small to medium-sized business. The 1901 has either 4,096, 8,192 or 16,384 words of core store with a cycle time of 6 microseconds. Like all 1900 Series processors, the word length in the store is 24 binary digits. Three standard interface channels are provided with provision for three more. The number of peripheral devices employed can however exceed the number of channels available because certain peripheral devices, for example a group of magnetic tape units, may be connected to one interface channel via a common control unit.

In addition to the already extensive range of peripheral units developed for the 1900 Series, further low-cost units have also been developed specifically to match the performance of the 1901. In particular, a new medium capacity magnetic tape system has been devised. This employs "cassette" storage that provides greater protection for the magnetic tape, thus greatly eliminating the need for expensive air conditioning, and providing far easier loading and unloading.

1902 and 1903 Processors: Capable of operating with single or dual programming Executive control, these processors can drive large numbers of peripheral devices with maximum simultaneity. They can be specified with communications facilities and therefore work in real time. The 1902 has 4,096, 8,192, 16,384 or 32,768 words of core store with a cycle time of 6 microseconds. The 1903 has 8,192 or 16,384 words with a cycle time of 1.8 microseconds or 32,768 words with a cycle time of 2 microseconds.

These processors are equipped with up to eight standard interface channels. A multiplexor unit could handle up to 63 communications lines.

Extended Mathematical Units: To provide on the 1901, 1902 and 1903 the high speed mathematical computing facilities more usually associated with the larger central processors, I.C.T. has developed special units that can be fitted and/or floating point arithmetic circuits and replace the slower extra-code facilities provided by the Executives. When one of these units is fitted no reprogramming is required, the appropriate unit being automatically used instead of the extra-code. In this way the speed of arithmetic can be measured by up to 90 times.

1904 and 1905 Processors: These are multi-programming machines and can handle up to four main programs, each with two sub-programs, at the same time. There is automatic protection against programs corrupting one another, and "Executive" allocates priority to the different jobs in accordance with the instructions of the operator. The 1904 and 1905 processors are available with 8,192, 16,384 or 32,768 words of 2 microseconds core store, and can accommodate 18 general channels, for devices such as paper tape and card equipment, and 5 fast channels, for fast peripherals such as magnetic tapes and discs. The 1905 has an autonomous floating point unit which works concurrently with other functions of the processor.

1906 and 1907 Processors: These are also multi­programming machines and have faster processing units than the 1904 and 1905. They handle up to 16 main programs each with 3 sub-programs, with full program protection and priority allocation.

They have core stores of 32,768 words which can be incremented to 262,144 words with a core store cycle time of either 2.1 or 1.1 microseconds. 1906 and 1907 have 18 general channels via standard interface and may be specified with as many fast channels as may be required.

A further enhancement to the productivity of the 1906 and 1907 is a choice of one or more store access controls which improve processing performance to an even greater extent. The 1907 has an autonomous floating point unit, which works concurrently with other functions of the processor.

Wide range of peripheral devices

Data Input

Punched Cards : 80 column card readers operate at 300 and 900 cards a minute. 40 column card readers operate at 600 cards a minute.

Paper Tape: Readers operate on 8 track paper tape, using the ISO 7 data bit code (5, 6.7 track may also be used), at 1,000 or 300 characters a second.

Magnetic Ink Character Recognition: The I.C.T. 8500 document sorter/reader reads magnetic ink encoded data and can sort documents at a speed of 1,200 a minute.

Universal Document Transport: This device can read mark coded documents in a range of size. Future variants will also be able to read ISO B fount alpha-numeric characters.

Data Output

Punched Cards: 80 column card punches operate at 33,100, 300 and 350 cards a minute.

Paper Tape: Paper tape punches operate at 110 characters a second.

Line Printers: Printers with 96,120 or 160 characters to the line operate at 300 or 600 or 1.350 lines per minute.


Magnetic Tape

The magnetic tape systems are to international standards and operate at 20,800, 41,700, 60,000 or 96,000 characters a second.

Four-deck, cassette loaded, magnetic tape operates at 10,000 characters a second.

Direct Access Storage

I.C.T. provides a wide selection of direct access stores.

Magnetic Drum: Three sizes of magnetic drum provide capacities of 131,072, 524,228 or 2,097,000 characters each. Up to four drums maybe linked to one Control.

Exchangeable Disc Stores: These comprise a number of disc transports. Each transport may be loaded by the operator with a disc cartridge, which comprises six discs with a capacity of 4,090,000 or 8,190,000 characters. The average access time is 97.5 milliseconds and the data transfer is 208,000 characters a second.

Fixed Disc Stores: Three versions are available, providing a capacity of 100,600,000, 218,400,000 or 419.400,000 characters. The average access time is 152.5 milliseconds and the transfer rate is 150,000 characters a second.

Magnetic Card File: Interchangeable magazines of magnetic cards give storage for 340,000,000 characters to each file unit. There can be multiple files in the 1900 system giving a maximum capacity of 5,400,000,000 characters. The average time to select a card is 393 milliseconds. Transfer rate between the file and central processor is 80,000 characters a second. Each file unit contains 8 magazines and each magazine stores over 40 million characters.



The cathode-ray tube (CRT) display presents the contents of any part of the storage as letters, figures or symbols on a display screen, which may be situated at a distance from the computer. It permits the display of vectors and graphical data and has light pen and 35 mm. camera options available, the latter operating at 20 frames per second. A further method of display is available in a range of graph plotters either 12" or 31" wide with step sizes of either 5 or 10 thousandths of an inch. Speeds are either 12 or 18 thousand steps per minute along either axis.


These allow a wide choice of transmission speed and type of communications circuit. Processors can be connected to one another remotely or within the same installation and can communicate with a variety of remote peripheral devices for data collection and distribution, and for interrogation of file data.