01-29-2011, 09:53 PM

Welcome to my boolean algebra tutorial series. This is going to be part one of a multi-part series. I'm not sure yet how many there will be.

What is boolean algebra? Well, boolean algebra is a deductive mathematical system closed over the values 0 and 1 (false and true respectively). Boolean logic is the basis for computation in binary computer systems. Any algorithm or electronic circuit can be represented by a system of boolean equations.

Boolean algebra uses binary operators. A binary operator accepts a pair of boolean inputs (1 or 0, true or false) and produces a single output based on them (again 1, 0, true, false). For example, the boolean AND operator accepts two inputs, ANDs them, and produces the result.

Postulates of boolean algebra:

Closure: the boolean system is closed with respect to a binary operator if for every pair of boolean values it produces a single boolean result.

example: Logical AND is closed because it accepts only boolean operands and produces only boolean results.

Commutativity: A binary operator * is commutative if A*B = B*A for all possible values of A and B.

Associativity: A binary operator * is associative if (A*B)*C = A*(B*C) for all possible values of A, B, and C.

Distribution: Two binary operators * and ` are distributive if A*(B`C) = (A*B)`(A*C) for all A, B, and C values.

Identity: A boolean value I is an identity element with respect to another operator * if A*I = A

Inverse: A boolean value I is the inverse element with repect to an operator * if A*I=B and B does not = A (meaning B is the opposite of A).

Now that we have the postulates covered, lets cover the usual operators.

The symbol * represents the logical AND operation. A*B is the result of logically ANDing boolean values A and B.

The symbol + represents the logical OR operation. A+B is the result of logically ORing boolean values A and B.

The symbol ' is logical NOT. ` is unary meaning that it has only one operand. A' is the result of NOTing A boolean value A.

The order of operations in boolean algebra are also important. The order goes parenteses (), NOT ', AND *, then OR +.

I really lied about the postulates. Those weren't all of them. These postulates cover specific operators though so they are a bit different.

Boolean Algebra is closed under AND, Or, and NOT

The identity element with repect to * is 1 and to + is 0.

There is not identity element with '

The * and + operators are commutative

* and + are distributive with repect to each other

Ex. A*(B+C)=(A*B)+(A*C) and A+(B*C)=(A+B)*(A+C)

For every value of A there is a A' so A*A'=0 and A+A'=1.

Those are all the postulates. We do, however, also have theorums that we have to cover. There are 16 important theorums.

1. A+A=A

2. A*A=A

3. A+0=A

4. A*1=A

5. A*0=0

6. A+1=1

7. (A+B)'=A'*A'

8. (A*B)'=A'+B'

9. A+A*B=A

10. A*(A+B)=A

11. A+A'*B=A+B

12. A'*(A+B')=A'*B'

13. A*B+A*B'=A

14. (A'+B')*(A'+B)=A'

15. A+A'=1

16. A*A'=0

Those are all 16 theorums that we're going to need. I know it can be a lot to take in at once so read over and review this so far. Next up we're going to be building boolean truth tables.

What is boolean algebra? Well, boolean algebra is a deductive mathematical system closed over the values 0 and 1 (false and true respectively). Boolean logic is the basis for computation in binary computer systems. Any algorithm or electronic circuit can be represented by a system of boolean equations.

Boolean algebra uses binary operators. A binary operator accepts a pair of boolean inputs (1 or 0, true or false) and produces a single output based on them (again 1, 0, true, false). For example, the boolean AND operator accepts two inputs, ANDs them, and produces the result.

Postulates of boolean algebra:

Closure: the boolean system is closed with respect to a binary operator if for every pair of boolean values it produces a single boolean result.

example: Logical AND is closed because it accepts only boolean operands and produces only boolean results.

Commutativity: A binary operator * is commutative if A*B = B*A for all possible values of A and B.

Associativity: A binary operator * is associative if (A*B)*C = A*(B*C) for all possible values of A, B, and C.

Distribution: Two binary operators * and ` are distributive if A*(B`C) = (A*B)`(A*C) for all A, B, and C values.

Identity: A boolean value I is an identity element with respect to another operator * if A*I = A

Inverse: A boolean value I is the inverse element with repect to an operator * if A*I=B and B does not = A (meaning B is the opposite of A).

Now that we have the postulates covered, lets cover the usual operators.

The symbol * represents the logical AND operation. A*B is the result of logically ANDing boolean values A and B.

The symbol + represents the logical OR operation. A+B is the result of logically ORing boolean values A and B.

The symbol ' is logical NOT. ` is unary meaning that it has only one operand. A' is the result of NOTing A boolean value A.

The order of operations in boolean algebra are also important. The order goes parenteses (), NOT ', AND *, then OR +.

I really lied about the postulates. Those weren't all of them. These postulates cover specific operators though so they are a bit different.

Boolean Algebra is closed under AND, Or, and NOT

The identity element with repect to * is 1 and to + is 0.

There is not identity element with '

The * and + operators are commutative

* and + are distributive with repect to each other

Ex. A*(B+C)=(A*B)+(A*C) and A+(B*C)=(A+B)*(A+C)

For every value of A there is a A' so A*A'=0 and A+A'=1.

Those are all the postulates. We do, however, also have theorums that we have to cover. There are 16 important theorums.

1. A+A=A

2. A*A=A

3. A+0=A

4. A*1=A

5. A*0=0

6. A+1=1

7. (A+B)'=A'*A'

8. (A*B)'=A'+B'

9. A+A*B=A

10. A*(A+B)=A

11. A+A'*B=A+B

12. A'*(A+B')=A'*B'

13. A*B+A*B'=A

14. (A'+B')*(A'+B)=A'

15. A+A'=1

16. A*A'=0

Those are all 16 theorums that we're going to need. I know it can be a lot to take in at once so read over and review this so far. Next up we're going to be building boolean truth tables.