Harvard Mark II

The Harvard Mark II was an electromechanical computer built at under the direction of Howard Aiken and was finished in 1947. It was financed by the United States Navy.

The Mark II was constructed with high-speed electromagnetic relays instead of electro-mechanical counters used in the Mark I, making it much faster than its predecessor. Its addition time was 0.125 seconds (8 Hz) and the multiplication time was 0.750 seconds. This was a factor of 2.6 faster for addition and a factor 8 faster for multiplication compared to the Mark I. It was the second machine (after the Bell Labs Relay Calculator) to have floating-point hardware. A unique feature of the Mark II is that it had built-in hardware for several functions such as the reciprocal, square root, logarithm, exponential, and some trigonometric functions. These took between five and twelve seconds to execute.

The Mark II was not a stored-program computer – it read an instruction of the program one at a time from a tape and executed it (like the Mark I). This separation of data and instructions is known as the Harvard architecture. The Mark II had a peculiar programming method that was devised to ensure that the contents of a register were available when needed. The tape containing the program could encode only eight instructions, so what a particular instruction code meant depended on when it was executed. Each second was divided up into several periods, and a coded instruction could mean different things in different periods. An addition could be started in any of eight periods in the second, a multiplication could be started in any of four periods of the second, and a transfer of data could be started in any of twelve periods of the second. Although this system worked, it made the programming complicated, and it reduced the efficiency of the machine somewhat.

Mark II

Mark II or Mark 2 often refers to the second version of a product, frequently military hardware. "Mark", meaning "model" or "variant", can be abbreviated "Mk."

Mark II or Mark 2 may refer to:

Military and weaponry

Vehicles

British heavy tanks of World War I

British heavy tanks were a series of related vehicles developed by the British Army during the First World War. The Mark I was the world's first tank to enter combat. Born of the need to break the domination of trenches, barbed wire and machine guns over the battlefields of the Western Front, it was the first vehicle to be named "tank", a name chosen as an expedient to maintain secrecy and to disguise its true purpose. It was developed to be able to cross trenches, resist small-arms fire, travel over difficult terrain, carry supplies, and to capture fortified enemy positions. It is regarded as successful in many respects, but suffered from many problems owing to its primitive nature.

The Mark I entered service in August 1916, and was first used in action on the morning of 15 September 1916 during the Battle of Flers-Courcelette, part of the Somme Offensive. With the exception of the few interim Mark II and Mark III tanks, it was followed by the largely similar Mark IV, which first saw combat in June 1917. The Mark IV was used en masse (about 460 tanks) at the Battle of Cambrai in November 1917. The Mark V, with its much improved transmission, entered service in mid-1918.

Mark II (robot)

Mark II is a rideable and user-operated robot built by the American company MegaBots Inc. The robot is scheduled to engage in a head-to-head fight with Kuratas, a robot built by Suidobashi Heavy Industry of Japan. Mark II made its debut in May 2015 at Maker Faire San Mateo. In August 2015, MegaBots announced plans to upgrade Mark II with melee capabilities in order to confront Kuratas, using funds from a Kickstarter campaign.

See also

References

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