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Z3 (computer): the story on HearLore | HearLore
Z3 (computer)
On the 21st of December 1943, a single Allied bombing raid erased the world's first working programmable digital computer from existence. The machine, known as the Z3, had been completed just two years prior in Berlin, yet it sat unused and largely forgotten by history until decades later. This electromechanical marvel, designed by a young civil engineer named Konrad Zuse, was built from 2,600 relays and operated at a sluggish clock frequency of 5 to 10 hertz. It was a massive, humming beast that consumed 4,000 watts of power and weighed several tons, yet it could only perform basic arithmetic operations like addition in 0.8 seconds and multiplication in 3 seconds. Despite its primitive speed by modern standards, the Z3 represented a radical leap forward because it was fully automatic and programmable, storing its instructions on a strip of punched celluloid film rather than requiring manual rewiring for every new task. The destruction of the original machine meant that for a long time, the world believed the concept of the computer was a purely post-war invention, obscuring the fact that the blueprint for the digital age had been drafted in the shadow of a collapsing empire.
From Mechanics To Relays
Konrad Zuse began his journey into computing with a wholly mechanical design called the Z1, which he built between 1935 and 1938. The Z1 was a fragile creation that could only function for a few minutes at a time before its complex gears and levers failed. It was a testament to Zuse's engineering ambition but a practical failure that demanded a new approach. A doctoral student named Helmut Schreyer advised Zuse to abandon mechanical parts in favor of electronic technology, specifically vacuum tubes. Schreyer demonstrated a circuit based on Boolean operations and flip-flops in 1938, envisioning a machine with 2,000 electron tubes. However, the scientific community of the time dismissed the idea as infeasible, noting that the largest operational electronic devices contained far fewer tubes. Zuse recalled that the institute members simply smiled at them when they proposed building electronic machines, telling them that the components had to be developed first. Faced with this rejection, Zuse made a pragmatic decision to implement the next design using relays, which were more reliable and available than vacuum tubes. This pivot led to the Z2, which was financially supported by Kurt Pannke and presented to the German Laboratory for Aviation in 1940. The Z2 worked, convincing the laboratory to partially finance the next design, setting the stage for the Z3.
The War Machine
The Z3 was constructed in 1941 as a highly secret project under the supervision of the Reich Air Ministry. Joseph Jennissen, a member of the Research-Leadership, acted as the government supervisor for orders placed with Zuse's company, ZUSE Apparatebau. An aerodynamicist named Herbert A. Wagner served as a further intermediary between Zuse and the ministry. The machine was designed to solve complex wing flutter problems for aircraft, based on the work of Hans Georg Küssner. Despite its advanced capabilities, the Z3 was never considered vital to the war effort and was never put into everyday operation. Zuse had asked the German government for funding to replace the relays with fully electronic switches, but the proposal was denied during World War II because such development was deemed not war-important. The machine operated with a 22-bit word length and stored its program on punched film, allowing it to execute complex calculations without rewiring. It was faster and far more reliable than its predecessors, the Z1 and Z2, and included improved floating-point arithmetic that could handle exceptions like plus infinity and minus infinity. The Z3 was originally called the V3, standing for Versuchsmodell 3 or Experimental Model 3, but was renamed to avoid confusion with Germany's V-weapons.
The Z3 computer was destroyed on the 21st of December 1943 during an Allied bombing raid on Berlin. This event erased the world's first working programmable digital computer from existence.
Who designed the Z3 computer and when was it completed?
Konrad Zuse designed the Z3 computer and completed it in 1941. The machine was constructed as a highly secret project under the supervision of the Reich Air Ministry.
What was the clock frequency of the Z3 computer?
The Z3 computer operated at a clock frequency of 5 to 10 hertz. This electromechanical marvel used 2,600 relays to perform basic arithmetic operations.
Was the Z3 computer Turing-complete?
Raúl Rojas demonstrated in 1998 that the Z3 computer was Turing-complete in principle. He showed that the machine could compute all possible answers and cancel out unneeded results to function as a universal computer.
Where is the reconstructed Z3 computer located today?
A modern reconstruction of the Z3 computer is located in the Konrad Zuse Museum in Hünfeld, Germany. Another fully functioning replica built in 1961 is on permanent display at the Deutsches Museum in Munich.
The Z3 operated as a stack machine with a stack of two registers, R1 and R2, creating a unique architecture for its time. The first load operation in a program would load the contents of a memory location into R1, and the next load operation would load the contents of a memory location into R2. Arithmetic instructions would operate on the contents of R1 and R2, leaving the result in R1 and clearing R2. A store operation would store the contents of R1 into a memory location, and clear R1. This system allowed for a streamlined flow of data that was distinct from the random access memory architectures that would emerge later. The machine also featured a read keyboard operation to read a number from the keyboard into R1 and clear R2, and a display instruction to show the contents of R1 and clear R2. The input and output were facilitated by a terminal with a special keyboard for input and a row of lamps to show results. The data memory consisted of 64 22-bit words, while the program memory was stored on punched celluloid tape. The arithmetic unit was binary floating-point, capable of adding, subtracting, multiplying, dividing, and calculating square roots. This specific instruction set provided a practical solution for the typical engineering applications of the 1940s, prioritizing workability over theoretical universality.
The Turing Paradox
For decades, the Z3 was thought to lack the ability to be a universal computer because it did not have a conditional branch instruction. It was possible to construct loops on the Z3, but without the ability to make decisions based on the result of a calculation, it seemed limited. However, in 1998, Raúl Rojas demonstrated that the Z3 was, in principle, Turing-complete. He proposed that the tape program would have to be long enough to execute every possible path through both sides of every branch. The machine would compute all possible answers, but the unneeded results would be canceled out in a process akin to speculative execution. Rojas concluded that from an abstract theoretical perspective, the computing model of the Z3 is equivalent to the computing model of today's computers, though from a practical perspective, and in the way the Z3 was really programmed, it was not equivalent to modern computers. This limitation belied the fact that the Z3 provided a practical instruction set for the typical engineering applications of the 1940s. Zuse's main goal at the time was to have a workable device to facilitate his work as a civil engineer, and the machine succeeded in that regard.
The Lost Legacy
The original Z3 was destroyed on the 21st of December 1943 during an Allied bombardment of Berlin, taking with it the physical evidence of the world's first working programmable digital computer. Konrad Zuse moved on to the Z4 design, which he completed in a bunker in the Harz mountains, alongside Wernher von Braun's ballistic missile development. When World War II ended, Zuse retreated to Hinterstein in the Alps with the Z4, where he remained for several years. The legacy of the Z3 was preserved only through the work of modern reconstructions. A modern reconstruction directed by Raúl Rojas and Horst Zuse started in 1997 and finished in 2003. It is now in the Konrad Zuse Museum in Hünfeld, Germany. Memory was halved to 32 words, and power consumption was reduced to about 400 watts. In 2008, Horst Zuse started a reconstruction of the Z3 by himself, which was presented in 2010 in the Konrad Zuse Museum in Hünfeld. A fully functioning replica was also built in 1961 by Zuse's company, Zuse KG, which is now on permanent display at the Deutsches Museum in Munich. These reconstructions have allowed historians and engineers to study the machine and understand its significance.
The Independent Pioneer
The success of Zuse's Z3 is often attributed to its use of the simple binary system, which was invented roughly three centuries earlier by Gottfried Leibniz. George Boole later used it to develop his Boolean algebra, and Claude Shannon introduced the idea of mapping Boolean algebra onto electronic relays in a seminal work on digital circuit design in 1937. Zuse, however, did not know of Shannon's work and developed the groundwork for his first computer, the Z1, independently. Zuse was inspired by Hilbert's and Ackermann's book on elementary mathematical logic, Principles of Mathematical Logic. His coworker Helmut Schreyer built an electronic digital experimental model of a computer using 100 vacuum tubes in 1942, but it was lost at the end of the war. An analog computer was built by the rocket scientist Helmut Hölzer in 1942 at the Peenemünde Army Research Center to simulate V-2 rocket trajectories. The Colossus, built by Tommy Flowers in 1943, and the Atanasoff-Berry computer in 1942 used thermionic valves and binary representation of numbers, but programming was by means of re-plugging patch panels and setting switches. The ENIAC computer, completed after the war, used vacuum tubes to implement switches and used decimal representation for numbers. Until 1948, programming was, as with Colossus, by patch leads and switches. The Manchester Baby of 1948 along with the Manchester Mark 1 and EDSAC both of 1949 were the world's earliest working computers that stored program instructions and data in the same space, implementing the stored-program concept which is frequently but erroneously attributed to a 1945 paper by John von Neumann and colleagues.