Konrad Zuse. Biography. Contributions. Zuse-Companies. Z3r. Tour-Zuse-Computer. Z23 Crosses Altlantic. Early Computers. Neumann vs Konrad Zuse. Impressum and Contact. Professor Dr.-Ing. habil.
Horst Zuse



Computer Z23,

restored by the

Konrad Zuse Schule in Hünfeld,

for the

Computer Museum History Center

in Mountain View (California)


Horst Zuse

October 12, 1999

1 Foreword

On April 30, 1999 19 students of the Konrad Zuse Schule (Konrad Zuse School) in Hünfeld, where Konrad Zuse lived from 1956 till his death in 1995, finished the assembly of the historical Computer Z23 of the Zuse KG for the delivery to the Computer Museum History Center in Mountain View (California) close to San Francisco. The Computer Museum History Center is a part of the Boston Computer Museum.

The students of the Class 11 IT of the Konrad Zuse Schule in Hünfeld restored together with the class teacher Bubenheim and Leopold Stein, who is a member of the Konrad Zuse Gesellschaft, the historical Z23 computer. The next picture shows the Z23 in 1961.

2  Story of Restoring the Historical Zuse Z23 Computer by the Konrad Zuse Schule

Professor Dr. Hermann Flessner (Hamburg), who is a member of the Konrad Zuse Gesellschaft, was the initiator of the Project Z23 in order to deliver the historical computer Z23 to USA. He created the contacts with Mr. Shustek of the Boston Computer Museum. This museum transferred some of his exhibitions on the history of computing from Boston to the west coast (Mountain View).

Leopold Stein, also a member of the Konrad Zuse Gesellschaft, organized and advised the students how to build up the many pieces of the Z23. Leopold Stein also will build up the Votis Software Museum in Hünfeld in the near future.

The lass 11 IT of the Konrad Zuse Schule (Konrad Zuse School, which is a vocational school) in Hünfeld, who restored the Computer Z23.

In the Foreword of the booklet we can read amongst others (Translated by Horst Zuse into English): In February 1999 the Konrad Zuse Gesellschaft asked the Konrad Zuse Schule, whether it is possible to restore the historical computer Z23, which was built by the Zuse KG from 1961.

It was a wish of Konrad Zuse, that one of his computers should be set up in a museum in the USA. The Class 11 IT under the leadership of the Teacher Bubenheim agreed to build up the Z23, which single pieces where set up in a store in Hünfeld.

At Monday, March 1, 1999 the pieces of the Z23 were delivered with a truck. By beginning of this project, the whole class visited the Konrad Zuse Abteilung in the Stadt- und Kreisgeschichtlichen Museum in Hünfeld (Konrad Zuse Section in the native museum in Hünfeld). There, another Z23 computer has been set up. At March 3, the class begun to restore the Z23.

The following students with the class teacher Bubenheim helped to restore the Z23:

   * Christian Becker

   * Dieter Befort

   * Lars Buecher

   * Stefan Eyrich

   * Peter Göbel

   * Stefan Göpfert

   * Angelika Happ

   * Sebastian henkel

   * Jens Jagusch

   * Alex Keller

   * Patric Matuszewski

   * Adam Miozga

   * Christian Most

   * Thomas Münkel

   * Christopf Naderer

   * Thomas Nelhübel

   * Michael Pachowski

   * Manual Päsold

   * Holger Rohde

The students made a lot of pictures of the Z23 in the Museum in order to understand the architecture of this machine. Firstly the heavily soiled Z23 had to be cleaned.

The students saw the first time transistors, resistors, capacitors, diodes and a real wiring.

To install the magnet drum of the Z23 was one of the most difficult tasks.

Picture 16: The magnetic drum of the Z23. The capacity was 8192 words. The rotation speed of the drum was 6000 rotations per minute.

The engine on the right side is a transformer from 380 Volt alternating current to direct current. The engine also equalized fluctuation of the electric power.

On the top of the arithmetic unit the power supplies have to be installed. The power consumption of the Z23 was around 4000 Watt.

The most sophisticated unit of the Z23 was the ferrit core memory with a capacity of 256 words a 40 bits.

On Friday, April 30, 1999, the work to restore the T23 was finished. Of course, this event had to be celebrated.

3 Friday, April 30, 1999 in Hünfeld

At Friday, April 30, 1999 Mr. Helmut Käsmann, who is responsible for public relations in Hünfeld, invited the following guest and TV-Stations in order to present the work of the students of the Konrad Zuse Schule for the public.

   * Hünfelder Zeitung.

   * Computer Magazin Konrad.

   * Computer Bild.

   * Bild Zeitung.

   * Radio FFH.

   * Hessischer Rundfunk.

   * ARD.

   * ZDF.

   * RTL.

   * SAT 1.

   * Pro 7./UL>

The following persons were invited for the celebration and the following press conference. They thanked the students, teachers, etc. for their excellent work:

Studiendirektor Stefan Schmitt, who is the director of the Konrad Zuse Schule in Hünfeld welcomed the guests.

Prof. Dr. Hermann Flessner, who initiated the project to deliver the Z23 to USA, explained the wish of Konrad Zuse to get a machine of him to USA.

Dr. Horst Zuse explained the importance of the Computer Z23 in the sixties and thanked the students and teachers for their excellent work.

Dr. Wilhelm Mons, the acting Chairman of the Konrad Zuse Gesellschaft, presented the task of the Konrad Zuse Gesellschaft.

Angelika Happe, a student of the Class 11 IT, presented very humorousness the work of the students. She said, that they are very sad to give away the machine Z23. It is a real big computer, which is totally different related to a motherboard of a PENTIUM Processor.

W. Vogt, a member of the city council (The major of Hünfeld

The major Dr. Eberhard Fennel could not come), thanked the students and teachers for their work.

3 Ackknowledgements

I am very grateful to the students and teachers of the Konrad Zuse Schule, to Prof. Hermann Flessner and Leopold Stein, who made it possible to restore a Zuse Z23 computer for the delivery to the Computer Museum History Center in Mountain View in California. We now show the Class 11 IT with their teachers, again.

I talked with the students and they listened very curious to my explanations how the Z23 worked. They asked me how the ferrit core memory worked and how this memory was constructed. In order to make them more curious to the history of computer development of Konrad Zuse but also in US I gave every student the Konrad Zuse Multimedia Show.

I also thank Dr. Leonard J. Shustek very much for his agreement and effort to exhibit the Z23 in the Computer Museum History Center. Prof. Dr. Flessner, Leopold Stein, Dr. Wilhelm Mons and me will go to the inauguration of the Z23 in Mountain View. We also will invite one student of the Class 11 IT to come with us to Mountain View.

Horst Zuse, May 1, 1999


The Zuse Z23 Computer (1961), which was delivered 98 times to universities and industry.
The Zuse Z23 Computer (1961) in the maximal configuration

Professor Dr. Hermann Flessner.
Leopold Stein, who lives in Hünfeld.
The students of the Class 11 IT of the Konrad Zuse Schule, who restored the Zuse Computer Z23. Left: The class teacher Bubenheim.
The boxes of the Z23 had to be cleaned up and to be set up.
The printed circuit boards of the Z23.
n this box the magnetic drum with a capacity of 8192 words a 40 bits has to be installed.
Picture 1: Mountain View (Mtn. View), where the Z23 will be delivered lies south of the San Francisco Bay, a little bit south of Palo Alto.
The input device of the Z23. If you want to see how the Z23 works, then use the Simulation of the Z23 by Bernd Nitzler
The control and arithmetic units of the Z23. The Z23 had an operation time of 10000 additions per
The inauguration of the Z23 computer in the Computer Museum History center took place on October 1, 1999. The Z23 arrived there in a good shape and is on exhibition. On the right side of the Z23 you can see a top secret computer system of the cold war. It was the SAGE compter system in order to control the flying intercontintal rockets of the UDSSR.