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Computer history LEOK:
Period 1964 - 1974

LEOK's own computer centre

At the end of the sixties, LEOK started to reserve funds to buy a computer system for a new to establish computer centre as part of the Laboratorium Elektronische Ontwikkelingen Krijgsmacht (LEOK). The primary objective was to buy a process-control computer. At the same time, the computer system had to be equipped with enough software and input/output equipment to support program development and scientific research purposes. After market analysis, a system configuration based upon the Ferranti FM 1600B-computer was recommended on grounds of price, delivery time and quality of the instruction set and organisation of the input/output.

The contract was placed end of 1969 (after some delays), causing a computerless-period between the end of the 3D-simulator project in 1970 and the acceptance of the Ferranti FM 1600B system.

In the mean time, limited spare capacity of the SIMREK system of the Royal Netherlands Navy in Den Helder could be used. Thus, the newly Computation/programming group (Rekenafdeling/programmeergroep) had to limit their activities to the preparation of the installation of LEOK's own Ferranti FM1600B computer. Fortunately, the RAREK computer became available earlier than expected as the 3D-project ended and the system was made available to the LEOK.

Ferranti FM1600B computer

Ferranti Ferranti
Ferranti Ferranti
Ferranti computer
(photo's made during the conveyance of the system)
Click thumbnail for enlarged photo

In the summer of 1971, LEOK's own Ferranti FM1600B was accepted. The photo's above, made during the conveyance of the system, give an impression of the total system and the input/output equipment.

The computer system comprised a central processing unit, 16K core memory (later 40K), 22 interrupt channels which connected the following input/output equipment:

Ferranti FM1600B The software comprised compilers for ALGOL 60, FORTRAN II and CORAL 64, a FIXPAC asembler, a subroutine library and utilities. CORAL 64 was at that time the NATO programming standaard, block structurered as Algol 60, for applications in real-time environments. The compiler had six passes! Calculations could be performed in integer, floating point, or fixed point (where the comma moved around). The advantage was an optimum precision and maximum speed.
FIXPAC (FixedPoint Autocode) was the assembler. Instructies were based on three adresses, e.g., Va=Vb+Vc - V was written as the Greek character 'nu').

Programs were started from papertape. During compilation of a program, multiple passes of the compilation process resulted in intermediate code on papertape. The computer was controlled from the operator panel. We developed our own operating system that allowed the use of magnetic tape. After these modifications the de bootstrap recognised the magnetic tape drive as a "boot device". We called that "BOS". Later on, a larger operating system "EOS" was loaded from magnetic tape . It had a simple command structure and a very universal IO-interface. A own-developed text editor, like the one on a PDP 8 was added. Compilers were disassembled and adapted to make use of the IO-interface("I recal that my collegue Pim O. worked hard for several months to get the Algol compiler working. Finally, it produced an "Eureka" stating "It is ok now, boys"). A Tektronix phosphorus memory screen was used as operator station. Finally the noisy Teletype could be switched off. The operasting system was sold to Ferranti for an extra block of memory. EOS was used, with disk instead of magnetic tape, for the Mechlua trainer project

An important project which used the Ferranti was Torpeval (2D-phase). Information recorded at ships of the Royal Netherlands Navy was processed by the LEOK. The outcome was presented in the form of tables and plots. Printing and plotting of the Torpeval results required the writing of Torpeval in assembly code. Later, LEOK changed the ALGOL and FORTRAN compiIers/runtime systems in such a way that the output devices could be addressed in a more high-level way causing programming to become quicker and easier.

The hardware was extended with the needed core memory till 32K (total) and a display-terminal.

The Ferranti system was used for:


Mechlua trainer

End of 1969, a 2400 baud synchronous terminal connection was made with the Control Data CDC 6400 of the Physics Laboratory RVO-TNO. Two TNO-collegues of the Prins Maurits Laboratory had implemented that code in Basic Plus, the standard language for the DEC Resource Time Sharing System or RSTS/E operating system on PDP-11's. Basic Plus was a completely unstructurered Basic derivative. It had statement modifiers: additional clauses placed at the end of a Basic statement. The kick was to write your program in only a limited number of statements, with one command spanning to more than half a page. At the same time, plans were developed to couple the RAREK to the CDC 6400 and to fit the Ferranti FM1600B with a time-sharing operating multi-user system. However, before these plans were realised, the Ferranti was replaced by a DIGITAL PDP 11/60. This configuration was extended later with a DIGITAL PDP 11/44 and a PDP 11/34.

The largest project of the LEOK during that period was the Mech Lua (Luchtafweer = Anti-air) Trainer (MLT) based on Ferranti FM1600B computers. These trainers are still (1998!) in use in Ede (they are 'retired' now). One of the TNO-FEL employees concluded in the beginning of 1998: "It is remarkable to see such a system still working, it even does not make a worn-out impression!"

Anecdote: Navy-blue papertape

An important LEOK project required the processing of measurements recorded in many hundreds of meters of papertape. The measurements were made on board of Royal Netherlands Navy ships. The problem was that the Ferranti had an "ultra modern" papertape reader which used light cells. Our Royal Netherlands Navy used mechanical papertape equipment and "cheap" white (uncolored) papertape. The light cells of the Ferranti papertape reader were extremely sensitive, causing "read-through" the Navy white papertape. In short, all "bit positions" were read as "holes".
Copying would be a tedious task and could introduce errors (given the reliability of equipment at that time). Secondly, LEOK possessed no papertape duplication equipment. Thus, one single option was left: coloring the papertape. Several bottles of ink were emptied in a wastepaperbasket. The papertapes were then slowly transported through the ink. After drying of the now (Navy)-blue papertape, the measurement data could be processed flawlessly.

Analog and hybrid computation

This section will be expanded in the future. More information about analog computation can be found in the museum of the University of Amsterdam.



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