# The Computer Lore – 4

The engineers assembled several logic gates

We describe here below a few such gates.

In all cases we always get the “perfect ones”

At front door irrespective of the input voltages

Which we give at the two back doors.

(We should remember that

“One” may mean a voltage say of “five” volts

And “zero” may mean a voltage of “ten” volts.

The electric voltages are low

And do not give you taste of any shock!)

In the first example the inputs at both back doors

Should only be “one” and “one”.

In the second case the inputs at the two back doors

Can be either “one” or “zero”

In the third case through the two back doors

We can send “zero and zero”

Or can send “one and zero”

There are many more cases

To ensure getting not only a “a perfect one”

But even a “perfect zero” through the front door!

There is a special “not” gate.

It has only one door at the back

And one door at the front.

If “one” goes in “zero” comes out

And if “zero” goes in “one” comes out!

The logic gates as you see are intelligent circuits

They imitate the situations

Which we encounter in life.

We say some times “I want both this and that”,

Some times “I want only this or that”

Some times the condition is “not this”

It is a most important condition

We can convert a “zero” into “one”

And a “one” into a “zero” as per our wish!

In further examples below

A and B are “inputting” doors

That lie on the back wall.

The outgoing zeroes and ones would pass

Through the door C at the front.

.

“You should complete both the works,

Then only I will pay you.”

It is realized in logic gate as below.

The “ones” (not “zeroes”) should enter at A and B.

Then only a “one” would comes out through C

“It is enough if you complete either work

Still I am ready to pay”

It is imitated thus in a logic circuit.

“If “one” enters in just through one back door

Either of the doors A or B

You can be sure of a “one”

Coming out of the front door C.

“You have not finished even one work

I warn you but still will pay.

But know this is the last such case”

The logic circuit imitates thus.

“Through the two back doors A and B

Only Boolean zeroes enter

But still a Boolean one comes out

Through C the door at the front.”

“I say sit down and you stand.

When I ask you to stand you sit.

What shall I do my silly little boy?”

This situation is imitated in the “not” logic gate.

“When zero comes in one goes out

When one comes in zero goes out”.

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