LRR1
The Logistic Relay Calculator 1 (LRR1), a logical machine , was developed in 1954 by Johann Weipoltshammer as part of his diploma thesis supervised by the young Heinz Zemanek .
The machine calculates the truth table or a part of it for a given propositional expression ( statement ) . LRR1 processes statements in a maximum of seven variables, which can contain up to 38 logical connective ( joiners ), of which a maximum of six conjunctions , disjunctions , conditional (= material implications), biconditional (object-language equivalence ) and negations as well as eight antivalences .
In principle, the statement is entered in Peano-Russell notation , an infix notation . The input is not made via the keyboard, but - not uncommon for the time - with cords. This creates contacts between sentence letter sockets and connective sockets. To express the conjunction "P and Q", one would proceed as follows:
- You connect one of the P contacts to the left input of a free conjuncture socket.
- Connect one of the Q contacts to the right input of the same conjunctive socket.
- The output of the conjuncture socket is connected to the input of the arithmetic unit.
Once you get used to this input logic, you can enter complex statements relatively quickly. Would you like B. To calculate "(P and Q) or R", i.e. the disjunction of the conjunction from the previous example and the sentence letter R, then one would proceed as follows:
- You plug in the example above, but do not connect the output of the conjuncture socket directly to the calculator, but to the left input of a free disjunction socket.
- One of the R contacts is connected to the right input of the same disjunction socket.
- Finally you connect the output of this disjunction socket with the input of the arithmetic unit.
Even if Weipoltshammer himself did not see it that way, one can understand this input logic directly as a tree notation, i.e. H. as a direct 1: 1 representation of the expression tree of the statement to be entered. The inserted cords represent the edges in the expression tree.
Using rotary telephone dials , the machine generates all truth value assignments in an orderly sequence for the sentence letters (sentence variables) that appear in the statement entered . The examined statement is evaluated under each of these assignments. The machine either stops after each step (if you want to write down every result in order to form a truth table in this way), or it continues to calculate until a result specified by the user ( true or false ) is reached (if you have would like to fulfill the statement or find a refutation).
The LRR1 needs a good one and a half minutes (100 seconds) to fully calculate a maximally complex statement. Today the machine is in the Deutsches Museum in Munich .
literature
- Johann Weipoltshammer: The logistic relay calculating machine LRR1 , Vienna 1954 (diploma thesis)
- Karl Weinhart (ed.): Computer science and automation. Guide through the exhibition , Deutsches Museum, Munich 1990
- Christian Gottschall: Logical notations and their processing on electronic computers from a theoretical, historical and practical point of view , Vienna 2005 (diploma thesis)
