Z3 (computer)

The Z3 was the world's first ever automatic, program-controlled computer. Built in the early 1940s by German civil engineer Konrad Zuse, the Z3 represented a significant breakthrough in the early development of computers. While the Z3 was primarily designed to complete general mathematical calculations like other computers of its time—including those created by such computer science giants as Howard Aiken, George Stibitz, and Alan Turing—it worked differently. The Z3 was unique because it was programmable and could complete its calculations automatically. For Zuse, who completed his machine in the midst of World War II and with little support from the embattled German government, the Z3's successful debut in 1941 was the culmination of years of work in computer science and the construction of two earlier models, the Z1 and Z2. Although it was certainly primitive by contemporary standards, the Z3 set the stage for the development of modern computers and helped usher in the digital age.

Background

As a young man, Zuse was primarily interested in art, but he also had a marked talent for engineering. Eventually, he chose to pursue a career as an engineer and enrolled at the Technical University of Berlin. After graduating in 1935, Zuse briefly worked as a structural engineer with the Henschel Aircraft Company, but soon left this job in favor of focusing on a different effort. During his time as a student and an actual engineer in the field, Zuse found the complex mathematical calculations that engineering required to be extremely slow and tedious. Determined to find a way to make completing such calculations easier, he turned his attention to computer science. Ultimately, Zuse decided to try his hand at building his own computer.

Setting up a makeshift laboratory in his parents' Berlin apartment and gathering a team of volunteer college friends to help with the effort, Zuse set to work on creating a calculating computer based on a binary system in which numeric values were represented using two different symbols (typically 1 and 0). Zuse's initial work led to the Z1, a mostly mechanical computer built with a memory unit and an arithmetic unit. Although the Z1 worked when it was completed in 1938, it did not work particularly well. Frequent problems with the gears and levers used for transmitting signals in the arithmetic unit meant that the Z1 would only work for short periods before breaking down. Upon realizing that electric wires could be used to carry signals more efficiently, Zuse quickly began making plans for a second computer.

In developing what would become the Z2, Zuse chose to include not only electrical wiring, but also telephone relays—small, electrically driven mechanical switches—in his design. These relays helped to shorten processing times and made the Z2 more efficient than its predecessor. Despite this improvement, however, the Z2 still proved to be unstable. Regardless, Zuse, who was drafted into the German army for a time during this period, demonstrated the Z2 at the German Aeronautics Research Institute (DLV) in 1940. Impressed with his work, DLV officials offered to provide Zuse with partial funding for his next project. With this support, Zuse returned home and began work on the Z3.

Overview

Once again working from his living room laboratory, Zuse built the Z3 with the help of his volunteer team. Work on the machine was completed on December 5, 1941. In terms of its design, the Z3 shared many similarities with its predecessors, but also had some key differences. Like the Z1 and Z2, the Z3 used discarded filmstrips for input instead of the punched paper tape that most other early computers used at the time. Also like Zuse's earlier models, the Z3 had a keyboard with four decimal places for entering data and an electric lamp used to display output. Unlike the Z1 and Z2, however, the Z3 was built with a much larger number of electromechanical relays—around 2,600 in total. About 1,400 of these relays were used in the memory unit alone. The Z3's arithmetic unit was composed of two different devices that separately handled different parts of numbers. Using this approach, Zuse was able to construct an arithmetic unit that could add, subtract, multiply, divide, and even find square roots. To make the Z3 as fast as possible, Zuse also programmed in a number of common multiplication problems. In part because of this, the Z3 was able to multiply two numbers in about four or five seconds and add two numbers together in anywhere from one-fourth to one-third of a second. For its time, the Z3 was a fast, cutting-edge computer.

While the Z3 had remarkable abilities and represented an important step forward in the evolution of computing, it could not otherwise be considered a success. When Zuse presented his newest machine at the DLV, officials there felt that because it had only limited memory space, the Z3 was not significantly more useful for their purposes than other existing methods of calculation. With the DLV showing no apparent interest in his work, Zuse was forced to take the Z3 back to his parents' apartment for storage. Unfortunately, the original Z3 was later destroyed during an Allied bombing raid on Berlin in 1944.

Following the DLV's rejection of the Z3, Zuse quickly began working on his next project, the Z4. Although his efforts were temporarily disrupted as Germany fell in the waning stages of World War II, Zuse eventually got the Z4 working. For a time, it was the only operational computer anywhere on the European mainland. Zuse finally found success after the war's end, establishing his own computer-manufacturing company, Zuse KG, which was absorbed into Siemens AG in 1967. In spite of his later successes, however, Zuse's crowning achievement remained the Z3. The Z3, as the first working program-controlled computer that could complete mathematic calculations, played an important role in the evolution of computer technology and contributed significantly to the development of modern computers and other similar high-tech devices. In fact, the Z3 may have been a more capable computer than Zuse himself ever realized. Two years after Zuse's death in 1995, researchers using a newly built replica of the original machine proved that the Z3 could solve any computable math problem if it was allowed enough time.

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