1977-09-19
1978-11-28
Hum, Vance Y.
35 9B, G09B 1902
Patent
active
041269497
ABSTRACT:
An educational calculator including a keyboard, a programmable logic array calculator circuit, an accumulator, a comparator, and two LED's for indicating whether the supposed answer is correct is disclosed. The keyboard includes a plurality of numerical input keys for entering operands and a supposed answer, a plurality of mathematical function keys for selecting mathematical functions, an "=" key, and test key. The programmable logic array is programmed for performing mathematical calculations selected by manipulation of the mathematical function keys upon operands entered by manipulation of the numerical input keys to produce a calculated answer. The answer is calculated upon subsequent manipulation of any mathematical function key or the "=" key. The accumulator stores the calculated answer. The programmable logic array is connected to the "=" key for being conditioned by manipulation of the "=" for subtracting from the calculated answer stored in the accumulator, a supposed answer entered upon subsequent manipulation of the numerical input keys. The comparator responds to manipulation of the test key by comparing the contents of the accumulator with zero. The LED's are of contrasting colors. They are connected to the comparator for indicating the results of the comparison. The green LED lights up in response to the comparison being made when the contents of the accumulator are zero, thereby indicating that the supposed answer entered subsequent to manipulation of the "=" key is correct. The red LED lights up in response to the comparison being made when the contents of the accumulator are not zero, thereby indicating that the entered supposed answer is incorrect.
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patent: 3925909 (1975-12-01), Duncan
patent: 3974575 (1976-08-01), Duncan
Hum Vance Y.
National Semiconductor Corporation
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