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Although based on relays, the Z3 was very sophisticated for its time; for example, it utilized the binary number system and could perform floatingpoint arithmetic which could be used for complicated arithmetic calculations. Konrad Zuse (19101995) also developed the first real programming language, Plankalkül (“Plan Calculus”) in 1944–45. Zuse's language allowed for the creation of procedures (stored chunks of code that could be invoked repeatedly to perform routine and subroutine operations such as taking a square root, and structured data (such as a record in a database, with a mixture of alphabetic and numeric data representing, for instance, name, address, and birth date). In addition, it provided conditional statements that could modify program execution, as well as repeat, or loop, statements that would cause a marked block of statements or a subroutine to be repeated a specified number of times or for as long as some condition held. Zuse was an amazing man who was years ahead of his time. To fully appreciate his achievements, it is necessary to understand that his background was in construction and civil engineering  not electronics. More information about Konrad Zuse and his computers: Konrad Zuse and his computers Konrad Zuse Internet Archive The Life and Work of Konrad Zuse  Wikipedia Konrad Zuse (1910  1995)  Kerry Redshaw Konrad Zuse  about.com The basic mechanical relay is an electromagnet that when activated, by attraction, opens or closes one or many sets of contacts. Konrad used relays to built logic gates  an arrangement of electronicallycontrolled switches used to calculate operations in Boolean algebra. Logic gates can also be constructed from diodes, fluidics, optical and mechanical elements. However, modern digital computers are built almost entirely from transistorized versions of these logic gates. Nikola Tesla filed the first patent for the AND logic gate in July 1900.
The general idea behind an AND gate is: If A AND B (both) take the logic value "1", then Q will be also "1", otherwise Q will take the logic value "0". This behavior is detailed in the truth table for the AND gate above. The same applies to the relay AND gate shown above: If we apply, both, A AND B points 6V, then Q will be 6V (otherwise Q will be 0V). This happens because when we apply 6V to both A and B, both relays R1 and R2 are activated and both contacts, which are connected in series, are closed and Q gets 6V. In other words, in a relay gate (or a transistorized one) the 1's and 0's are replaced by two different voltage values, in our case 6V and 0V (ground) respectively (other voltage values are also possible). In the same way we can also build an OR relay logic gate, but with one modification, instead of the two relay contacts being connected in series, like the case of the AND gate, the contacts will be connected in parallel. The same explanation applies to other logic gates (though different truth tables)  NOT, XOR, NOR, NAND which all of them could be build from relays. More about Logic Gates and Relays: Relays and Adder/Subtractors  Prof. William T. Verts Electromechanical Relays  Paul Smart Implementing Gates with Relays  howstuffworks Relay  Wikipedia Logic Gate  Wikipedia
Binary Adder  Wikipedia Simple Adders  howstuffworks Relays and Adder/Subtractors  Prof. William T. Verts Adding Binary Numbers  Ken Bigelow Half Adders, Full Adders, Ripple Carry Adders  Charles C. Lin Half and Full Adders  Doug Gingrich A Binary Adder  Donn Stewart Boolean Algebra Tutorials Boolean Algebra  Duncan Gillies Boolean Algebra  David Belton The Mathematics of Boolean Algebra  J. Donald Monk, Stanford Encyclopedia of Philosophy Boolean Algebra Tutorial  Basic Electronics Tutorials by Wayne Storr Universal Functions of Boolean Algebra  BBC Digital Logic  HyperPhysics Boolean Algebra and Logic Circuits  Deepak Kumar Tala 

