Simple Calculator With 7 segment display

Hello!
Today i will show my simple calculator.
He can make | A +B +C = D |
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My calculator is just Decimal binary decoder(1,2,4,8) + 7segment display
The maxium number is 15 (1+2+4+8=15)
This is the most compact calculator i´ve created (4 calculator) i dont no a lot about the redstone i start reading about redstone since 1 week or 2

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Simple calculator with screen http://www.planetminecraft.com/project/simple-calculator-with-screen/
Automatic Map: http://www.planetminecraft.com/project/automatic-map/
2digits clock (2bit): http://www.planetminecraft.com/project/2-digits-clock-2bit/
My Clock: http://www.planetminecraft.com/project/my-clock/
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Remember leave a Diamond :D