C.S. Scholten

In the summer of 1947, I was on vacation in Almelo. Earlier that year,
on the same day as my best friend and inseparable study mate, Brain
Jan Loopstra, I had successfully passed the qualifying exams in
mathematics and physics. The mandatory brief introduction to the three
major laboratories���the Physics Laboratory, the V.d. Waals Laboratory,
and the Zeeman Laboratory���was behind us, and we were about to start
our doctoral studies in experimental physics. For two years, we would
be practically working in one of the aforementioned laboratories.

One day, I received a telegram in Almelo with approximately the
following content: "Would you like to assist in building an automatic
calculating machine?" For assurance, another sentence was added:
"Mr. Loopstra has already agreed." The sender was "The Mathematical
Center," according to further details, located in Amsterdam. I briefly
considered whether my friend had already confirmed my cooperation, but
in that case, the telegram seemed unnecessary, so I dismissed that
assumption. Both scenarios were equally valid: breaking up our
long-standing cooperation (dating back to the beginning of high
school) was simply unthinkable. Furthermore, the telegram contained
two attractive points: "automatic calculating machine" and
"Mathematical Center," both new concepts to me. I couldn���t deduce more
than the name suggested. Since the cost of a telegram exceeded my
budget, I posted a postcard with my answer and resumed my vacation
activities. Those of you who have been involved in recruiting staff
will, I assume, be filled with admiration for this unique example of
recruitment tactics: no fuss about salary or working hours, not to
mention irrelevant details like pension, vacation, and sick leave. For
your reassurance, it should be mentioned that I was indeed offered a
salary and benefits, which, in our eyes, were quite generous.

I wasn't too concerned about how the new job could be combined with
the mandatory two-year laboratory work. I believed that a solution had
to be found for that. And a solution was found: the laboratory work
could be replaced by our work at the Mathematical Center.

Upon returning to Amsterdam, I found out the following: the
Mathematical Center was founded in 1946, with a goal that could
roughly be inferred from its name. One of the departments was the
'Calculation Department,' where diligent young ladies, using hand
calculators���colloquially known as 'coffee grinders'���numerically
solved, for example, differential equations (in a later stage,
so-called 'bookkeeping machines' were added to the machinery). The
problems dealt with usually came from external clients. The head of
the Calculation Department was Dr. ir. A. van Wijngaarden. Stories
about automatic calculating machines had also reached the management
of the Mathematical Center, and it was clear from the outset that such
a tool���if viable���could be of great importance, especially for the
Calculation Department. However, it was not possible to buy this
equipment; those who wanted to discuss it had to build it
themselves. Consequently, it was decided to establish a separate group
under the Calculation Department, with the task of constructing an
automatic calculating machine. Given the probable nature of this
group���s activities, it was somewhat an oddity within the Mathematical
Center, doomed to disappear, if not after completing the first
machine, then certainly once this kind of tool became a normal trade
object.

We were not the only group in the Netherlands involved in constructing
calculating machines. As we later discovered, Dr. W.L. v.d. Poel had
already started constructing a machine in 1946.

Our direct boss was Van Wijngaarden, and our newly formed two-man
group was temporarily housed in a room of the Physics Laboratory on
Plantage Muidergracht, where Prof. Clay was in charge. Our first
significant act was the removal of a high-voltage installation in the
room, much to the dismay of Clay, who was fond of the thing but
arrived too late to prevent the disaster. Then we thought it might be
useful to equip the room with some 220V sockets, so we went to
Waterlooplein and returned with a second-hand hammer, pliers,
screwdriver, some wire, and a few wooden (it was 1947!) sockets. I
remember wondering whether we could reasonably submit the exorbitant
bill corresponding to these purchases. Nonetheless, we did.

After providing our room with voltage, we felt an unpleasant sensation
that something was expected from us, though we had no idea how to
start. We decided to consult the sparse literature. This investigation
yielded two notable articles: one about the ENIAC, a digital (decimal)
computer designed for ballistic problems, and one about a differential
analyzer, a device for solving differential equations, where the
values of variables were represented by continuously variable physical
quantities, in this case, the rotation of shafts. The first article
was abominably written and incomprehensible, and as far as we
understood it, it was daunting, mentioning, for instance, 18,000
vacuum tubes, a number we were sure our employer could never
afford. The second article (by V. Bush), on the other hand, was
excellently written and gave us the idea that such a thing indeed
seemed buildable.

Therefore, it had to be a differential analyzer, and a mechanical one
at that. As we now know, we were betting on the wrong horse, but
first, we didn���t know that, and second, it didn���t really
matter. Initially, we were not up to either task simply because we
lacked any electronic training. We were supposed to master electricity
and atomic physics, but how a vacuum tube looked inside was known only
to radio amateurs among us, and we certainly were not. Our own
(preliminary) practicum contained, to my knowledge, no experiment in
which a vacuum tube was the object of study, and the physics practicum
for medical students (the so-called 'medical practicum'), where we had
supervised for a year as student assistants, contained exactly one
such experiment. It involved a rectifier, dated by colleagues with
some training in archaeology to about the end of the First World
War. The accompanying manual prescribed turning on the 'plate voltage'
only tens of seconds after the filament voltage, and the students had
to answer why this instruction was given. The answers were sometimes
very amusing. One such answer I won���t withhold from you: 'That is to
give the current a chance to go around once.'

Our first own experiment with a vacuum tube would not have been out of
place in a slapstick movie. It involved a triode, in whose anode
circuit we included a megohm resistor for safety. Safely ensconced
behind a tipped-over table, we turned on the 'experiment.' Unlike in a
slapstick movie, nothing significant happened in our case.

With the help of some textbooks, and not to forget the 'tube manuals'
of some manufacturers of these useful objects, we somewhat brushed up
on our electronic knowledge and managed to get a couple of components,
which were supposed to play a role in the differential analyzer, to a
state where their function could at least be guessed. They were a
moment amplifier and a curve follower. How we should perfect these
devices so that they would work reliably and could be produced in some
numbers remained a mystery to us. The solution to this mystery was
never found. Certainly not by me, as around this time (January 1948),
I was summoned to military service, which couldn���t do without
me. During the two years and eight months of my absence (I returned to
civilian life in September 1950), a drastic change took place, which I
could follow thanks to frequent contacts with Loopstra.

First, the Mathematical Center, including our group, moved to the
current building at 2nd Boerhaavestraat 49. The building looked
somewhat different back then. The entire building had consisted of two
symmetrically built schools. During the war, the building was
requisitioned by the Germans and used as a garage. In this context,
the outer wall of one of the gymnasiums was demolished. Now, one half
was again in use as a school, and the other half, as well as the attic
above both halves, was assigned to the Mathematical Center. The
Germans had installed a munitions lift in the building. The lift was
gone, but the associated lift shaft was not. Fortunately, few among us
had suicidal tendencies. The frosted glass in the toilet doors (an old
school!) had long since disappeared; for the sake of decorum, curtains
were hung in front of them.

Van Wijngaarden could operate for a long time over a hole in the floor
next to his desk, corresponding with a hole in the ceiling of the room
below (unoccupied). Despite his impressive cigar consumption at that
time, I didn���t notice that this gigantic ashtray ever filled up.

The number of employees in our group had meanwhile expanded somewhat;
all in all, perhaps around five.

The most significant change in the situation concerned our further
plans. The idea of a differential analyzer was abandoned as it had
become clear that the future belonged to digital computers. Upon my
return, a substantial part of such a computer, the 'A' (Automatische
Relais Rekenmachine Amsterdam), had already been realized. The main
components were relays (for various logical functions) and tubes (for
the flip-flops that composed the registers). The relays were Siemens
high-speed relays (switching times in the order of a few
milliseconds), personally retrieved by Loopstra and Van Wijngaarden
from an English war surplus. They contained a single changeover
contact (break-before-make), with make and break contacts rigidly set,
although adjustable. Logically appealing were the two separate coils
(with an equal number of windings): both the inclusive and exclusive
OR functions were within reach. The relays were mounted on octal bases
by us and later enclosed in a plastic bag to prevent contact
contamination.

They were a constant source of concern: switching times were
unreliable (especially when the exclusive OR was applied) and contact
degradation occurred nonetheless. Cleaning the contacts ('polishing
the pins') and resetting the switching times became a regular pastime,
often involving the girls from the Calculation Department. The setting
was done on a relay tester, and during this setting, the contacts were
under considerable voltage. Although an instrument with a wooden
handle was used for setting, the curses occasionally uttered suggested
it was not entirely effective.

For the flip-flops, double triodes were used, followed by a power tube
to drive a sufficient number of relays, and a pilot lamp for visual
indication of the flip-flop state. Since the A had three registers,
each 30 bits wide, there must have been about 90 power tubes, and we
noted with dismay that 90 power tubes oscillated excellently. After
some time, we knew exactly which pilot lamp socket needed a 2-meter
wire to eliminate the oscillation.

At a later stage, a drum (initially, the instructions were read from a
plugboard via step switches) functioned as memory; for input and
output, a tape reader (paper, as magnetic tape was yet to be invented)
and a teleprinter were available. A wooden kitchen table served as the
control desk.

Relays and tubes might have been the main logical building blocks, but
they were certainly not the only ones. Without too much exaggeration,
it can be said that the A was a collection of what the electronic
industry had to offer, a circumstance greatly contributed to by our
frequent trips to Eindhoven, from where we often returned with some
'sample items.' On the train back, we first reminisced about the
excellent lunch we had enjoyed and then inventoried to determine if we
brought back enough to cover the travel expenses. This examination
usually turned out positive.

It should be noted that the A was mainly not clocked. Each primitive
operation was followed by an 'operation complete' signal, which in
turn started the next operation. It is somewhat amusing that nowadays
such a system is sometimes proposed again (but hopefully more reliable
than what we produced) to prevent glitch problems, a concept we were
not familiar with at the time.

Needless to say, the A was so unreliable that little productive work
could be done with it. However, it was officially put into use. By
mid-1952, this was the case. His Excellency F.J. Th. Rutten, then
Minister of Education, appeared at our place and officially
inaugurated the A with some ceremony. For this purpose, we carefully
chose a demonstration program with minimal risk of failure, namely
producing random numbers �� la Fibonacci. We had rehearsed the
demonstration so often that we knew large parts of the output sequence
by heart, and we breathed a sigh of relief when we found that the
machine produced the correct output. In hindsight, I am surprised that
this demonstration did not earn us a reprimand from
higher-ups. Imagine: you are the Minister of Education, thoroughly
briefed at the Department about the wonders of the upcoming computing
machines; you attend the official inauguration, and you are greeted by
a group explaining that, to demonstrate these wonders, the machine
will soon produce a series of random numbers. When the moment arrives,
they tell you with beaming faces that the machine works excellently. I
would have assumed that, if not with the truth, at least with me, they
were having a bit of fun. His Excellency remained friendly, a
remarkable display of self-control.

The emotions stirred by this festivity were apparently too much for
the A. After the opening, as far as I recall, no reasonable amount of
useful work was ever produced. After some time, towards the end of
1952, we decided to give up the ARRA as a hopeless case and do
something else. There was another reason for this decision. The year
1952 should be considered an excellent harvest year for the
Mathematical Center staff: in March and November of that year, Edsger
Dijkstra and Gerrit Blaauw respectively appeared on the scene. Of
these two, the latter is of particular importance for today's story
and our future narrative. Gerrit had worked on computers at Harvard,
under the supervision of Howard Aiken. He had also written a
dissertation there and was willing to lend his knowledge and insight
to the Mathematical Center. We were not very compliant boys at that
time. Let me put it this way: we were aware that we did not have a
monopoly on wisdom, but we found it highly unlikely that anyone else
would know better. Therefore, the 'newcomer' was viewed with some
suspicion. Gerrit���s achievement was all the greater when he convinced
us in a lecture of the validity of what he proposed. And that was
quite something: a clocked machine, uniform building blocks consisting
of various types of AND/OR gates and corresponding amplifiers,
pluggable (and thus interchangeable) units, a neat design method based
on the use of two alternating, separate series of clock pulses, and
proper documentation.

We were sold on the plan and got to work. A small difficulty had to be
overcome: what we intended to do was obviously nothing more or less
than building a new machine, and this fact encountered some political
difficulties. The solution to this problem was simple: formally, it
would be a 'revision' of the A. The new machine was thus also called A
(we shall henceforth speak of A II), but the double bottom was
perfectly clear to any visitor: the frames of the two machines were
distinctly separated, with no connecting wire between them.

For the AND/OR gates, we decided to use selenium diodes. These usually
arrived in the form of selenium rectifiers, a sort of firecrackers of
varying sizes, which we dismantled to extract the individual rectifier
plates, about half the diameter of a modern-day dime. The assembly���the
selenium plates couldn't tolerate high temperatures, so soldering was
out of the question���was as follows: holes were drilled in a thick
piece of pertinax. One end of the hole was sealed with a metal plug;
into the resulting pot hole went a spring and a selenium plate, and
finally, the other end of the hole was also sealed with a metal
plug. For connecting the plugs, we thought the use of silver paint was
appropriate, and soon we were busy painting our first own
circuits. Some time later, we had plenty of reasons to curse this
decision. The reliability of these connections was poor, to put it
mildly, and around this time, the 'high-frequency hammer' must have
been invented: we took a small hammer with a rubber head and rattled
it along the handles of the units, like a child running its hand along
the railings of a fence. It proved an effective means to turn
intermittent interruptions into permanent ones. I won't hazard a guess
as to how many interruptions we introduced in this way. At a later
stage, the selenium diodes were replaced by germanium diodes, which
were simply soldered.

The AND/OR gates were followed by a triode amplifier and a cathode
follower. A II also got a drum and a tape reader. For output, an
electric typewriter was installed, with 16 keys operable by placing
magnets underneath them. The decoding tree for these magnets provided
us with the means to build an echo-check, and Dijkstra fabricated a
routine where, simultaneously with printing a number, the same number
(if all went well) was reconstructed. I assume we thus had one of the
first fully controlled print routines. Characteristic of A II���s speed
was the time for an addition: 20 ms (the time of a drum rotation).

A II came into operation in December 1953, this time without
ministerial assistance, but it performed significantly more useful
work than its predecessor, despite the technical difficulties outlined
above.

The design phase of A II marks for me the point where computer design
began to become a profession. This was greatly aided by the
introduction of uniform building blocks, describable in a
multidimensional binary state space, making the use of tools like
Boolean algebra meaningful. We figured out how to provide ARRA II with
signed multiplicative addition for integers (i.e., an operation of the
form (A,S) := (M) * (��S') + (A), for all sign combinations of (A),
(S), and (M) before and of the result), despite the fact that ARRA II
had only a counter as wide as a register. As far as I can recall, this
was the first time I devoted a document to proving that the proposed
solution was correct. Undoubtedly, the proof was in a form I would not
be satisfied with today, but still... It worked as intended, and you
can imagine my amusement when, years later, I learned from a French
book on computers that this problem was considered unsolvable.

In May 1954, work began on a (slightly modified) copy of ARRA II, the
FERTA (Fokker's First Calculating Machine Type A), intended for
Fokker. The FERTA was handed over to Fokker in April 1955. This entire
affair was mainly handled by Blaauw and Dijkstra. Shortly thereafter,
Blaauw left the service of the Mathematical Center.

In June 1956, the ARMAC (Automatic Calculating Machine Mathematical
Center), successor to A II, was put into operation, several dozen
times faster than its predecessor. Design and construction took about
1�� years. Worth mentioning is that the ARMAC first used cores, albeit
on a modest scale (in total 64 words of 34 bits each, I believe). For
generating the horizontal and vertical selection currents for these
cores, we used large cores. To drive these large cores, however, they
had to be equipped with a coil with a reasonable number of
windings. Extensive embroidery work didn���t seem appealing to us, so
the following solution was devised: a (fairly deep) rim was turned
from transparent plastic. Thus, we now had two rings: the rim and the
core. The rim was sawed at one place, and the flexibility of the
material made it possible to interlock the two rings. Then, the coil
was applied to the rim by rotating it from the outside using a rubber
wheel. The result was a neatly wound coil. The whole thing was then
encased in Araldite. The unintended surprising effect was that, since
the refractive indices of the plastic and Araldite apparently differed
little, the plastic rim became completely invisible. The observer saw
a core in the Araldite with a beautifully regularly wound coil around
it. We left many a visitor in the dark for quite some time about how
we produced these things!

The time of amateurism was coming to an end. Computers began to appear
on the market, and the fact that our group, which had now grown to
several dozen employees, did not really belong in the Mathematical
Center started to become painfully clear to us. Gradual dissolution of
the group was, of course, an option, but that meant destroying a good
piece of know-how. A solution was found when the Nillmij, which had
been automating its administration for some time using Bull punch card
equipment, declared its willingness to take over our group as the core
of a new Dutch computer industry. Thus it happened. The new company,
N.V. Elektrologica, was formally established in 1956, and gradually
our group���s employees were transferred to Elektrologica, a process
that was completed with my own transfer on January 1, 1959. As the
first commercial machine, we designed a fully transistorized computer,
the XI, whose prototype performed its first calculations at the end of
1957. The speed was about ten times that of the ARMAC.

With this, I consider the period I had to cover as concluded. When I
confront my memories with the title of this lecture, it must be said
that 'designing computers' as such hardly existed: the activities that
could be labeled as such were absorbed in the total of concerns that
demanded our attention. Those who engaged in constructing calculating
machines at that time usually worked in very small teams and performed
all the necessary tasks. We decided on the construction of racks,
doors, and closures, the placement of fans (the ARMAC consumed 10
kW!), we mounted power distribution cabinets and associated wiring, we
knew the available fuses and cross-sections of electrical cables by
heart, we soldered, we peered at oscillographs, we climbed into the
machine armed with a vacuum cleaner to clean it, and, indeed,
sometimes we were also involved in design.

We should not idealize. As you may have gathered from the above, we
were occasionally brought to the brink of despair by technical
problems. Inadequate components plagued us, as did a lack of knowledge
and insight. This lack existed not only in our group but globally the
field was not yet mastered.

However, it was also a fascinating time, marked by a constant sense of
'never before seen,' although that may not always have been literally
true. It was a time when organizing overtime, sometimes lasting all
night, posed no problem. It was a time when we knew a large portion of
the participants in international computer conferences at least by
sight!