Turing Complete

Turing Complete

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Turing Complete: Basic Logic-Solution
Tekijältä qwerty
Solution and explanation for levels in "Basic Logic".
This guide is subject to change.
   
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Quick Notes
NOT Gates
NOT gates (inverters) are 1-input gates that output the value opposite of the input. The negation of A is denoted by [A] (complement).
A
[A]
0
1
1
0


AND Gates
AND gates are 2-input gates that output 1 if both two inputs are 1. The conjunction of A and B is denoted by AB (product).
A
B
AB
0
0
0
1
0
0
0
1
0
1
1
1


OR Gates
OR gates are 2-input gates that output 1 if one of two inputs is 1. The disjunction of A and B is denoted by A+B (sum).
A
B
A+B
0
0
0
1
0
1
0
1
1
1
1
1


XOR Gates
XOR gates are 2-input gates that output 1 if two inputs are different. The exclusive disjunction of A and B is denoted by A{+}B (direct sum).
A
B
A{+}B
0
0
0
1
0
1
0
1
1
1
1
0


Useful Properties
Property
NOT
AND
OR
XOR
Commutativity
AB=BA
A+B=B+A
A{+}B=B{+}A
Associativity
(AB)C=A(BC)
(A+B)+C=A+(B+C)
(A{+}B){+}C=A{+}(B{+}C)
Distributivity
OR: A(B+C)=AB+AC
XOR: A(B{+}C)=AB{+}AC
AND: A+BC=(A+B)(A+C)
Identity
A1=A
A+0=A
A{+}0=A
Absorption
A0=0
A+1=1
Inversion
A{+}1=[A]
Complement
A[A]=0
A+[A]=1
A{+}[A]=1
Doubling
AA=A
A+A=A
A{+}A=0
Negation
De Morgan's Law
[[A]]=A
NAND
[AB]=[A]+[B]
NOR
[A+B]=[A][B]
XNOR
[A{+}B]=[A]{+}B=A{+}[B]
NAND Gate
NAND is the negation of AND, so the output is inverted.
NOT Gate
AA=A, so [AA]=[A].
AND Gate
The double negation of a value remains unchanged.
OR Gate
[A+B]=[A][B], so A+B=[[A][B]] and both inputs are inverted.
NOR Gate
NOR is the negation of OR, so the output is inverted.
Always On
A+[A]=1.
Second Tick
The output is 1 only if A=1 and B=0, so A[B] satisfies the requirement.
XOR Gate
XOR means the output is 1 when either one of two inputs is 1 but not both, so the desired circuit should be (A+B)[AB].




4 NAND Gates
We can simplify the expression
(A+B)[AB] as below:
  • (A+B)[AB]
  • A[AB]+B[AB] (distributive property)
  • [[A[AB]+B[AB]]] (double negation)
  • [[A[AB]][B[AB]]] (De Morgan's law)
Bigger AND Gate
A0=0, so the output of bigger AND is 0 if one of its inputs is 0.
Bigger OR Gate
A+1=1, so the output of bigger OR is 1 if one of its inputs is 1.
XNOR Gate
XNOR is the negation of XOR, so the output is inverted.