Magnetic Drum Digital Differential Analyzer | 1949

 

MADDIDA (Magnetic Drum Digital Differential Analyzer) is a special-purpose digital computer used to solve systems of ordinary differential equations. It was the first computer to use bit representation as voltage levels and the first to define its entire logic in Boolean algebra. Invented by Floyd Steele, MADDIDA was developed by Northrop Aircraft from 1946 to 1949 and was designed for use in the guidance system of the Snark missile. However, MADDIDA was not used in any weapon systems and instead found applications in aeronautical research. By 1952, MADDIDA became the best-selling commercial digital computer in the world, with six units sold.

Development

Development began in March 1946 at Northrop Aircraft, with the goal of creating a guidance system capable of striking targets accurately within 200 yards (180m) at distances of up to 5,000 miles (8,000km). However, MADDIDA was not used in weapon systems, and Northrop used a different analog computer for the Snark missile guidance.

As part of the project, the development of the first digital data analyzer (DIDA) was included. Floyd Steele was the leading figure behind the concept of DIDA, proposing a way to implement an analog computer using only digital elements. With the decision to use magnetic drum memory, the name was changed to MADDIDA.

Steele assembled a team to work on MADDIDA’s German-style diode logic circuits and magnetic recording, developing the MADDIDA prototype from 1946 to 1949.

Design

MADDIDA utilized a magnetic drum with six storage tracks to implement 44 integrators. Connections between the integrators were specified by recording the appropriate bit patterns on a single track. MADDIDA was the first computer to represent bits as voltage levels rather than electrical pulses and the first to define its entire logic in Boolean algebra. These features marked an advancement over previous digital computers, which still incorporated analog circuit components.

The original MADDIDA prototype is preserved in the collection of the Computer History Museum in Mountain View, California.

Distribution

Ultimately, MADDIDA was not used in weapon systems, and Northrop opted for a different analog computer system to guide the Snark missile. This system was unreliable, leading to the loss of many missiles; one missile launched in 1956 landed in northeastern Brazil and was not found until 1983. Many people involved in the program jokingly remarked that “the Caribbean is filled with ‘Snark-infested waters.’”

After the MADDIDA design team left Northrop in 1950, another team, including Max Palevsky, worked to commercialize the machine. By the end of 1952, six MADDIDAs were delivered, making it the best-selling commercial digital computer at that time. One of the six was sold to the Navy Electronics Laboratory.

Aftermath

Through the development of MADDIDA, the design team realized that a digital differential analyzer could be executed on general-purpose digital computers using appropriate problem-oriented languages (POL), such as DynamO. Following MADDIDA’s first demonstration, Steele and the design team left Northrop to develop general-purpose computers. On July 16, 1950, they founded the Computer Research Corporation (CRC), which was sold to NCR in 1953.

Max Palevsky, who had worked with the MADDIDA replication team at Northrop, went on to work on early personal computers like the Bendix G-15 from 1952 to 1956, eventually joining a new subsidiary of Packard Bell. Palevsky was able to continue design developments with commercial support for digital computing. He retired from his position as a director and chairman at Xerox in May 1972. While Xerox eventually abandoned personal computing, their prototypes influenced Steve Jobs and Steve Wozniak during their visit to Xerox facilities in 1979.