The computer instruction
The “computer instruction” is a sentence
(Like any sentence in our human languages)
But it is written in accurate 010101 code
With rigid discipline and mathematical accuracy
Using these instructions a human engineer speaks
To CPU which is the computer’s brain
The instruction is written in special technical code
Using English like “reserved words”
And also symbols like comma,full stop,
Brackets and quotation marks.
When a person is asked to do a work
We generally tell him somewhat like this
“First do this work….
“Then do that work
“Then go to that place…..
“Then meet that man….”
And so on and so forth
Similarly when solving an algebra problem
We write several steps in the working
The problem is solved step by step.
Same is the case with a “computer program”.
The “program” is nothing
But a set of rigid and serially numbered “instructions”
Sent by human engineer to the CPU
The CPU is not a living thing.
It has no thinking brain like humans.
It is only a slave of the human engineer
And fixed inside computer
To implement the person’s written instructions
Without the least little mistake
Its” thinking and actions”
Are only standard electric pulses
Corresponding to the “instructions”
Each instruction is implemented
Through several standard “microinstructions”
Prepared by the manufacturer of computer
And automatically preloaded
Into a specified section of the “main memory board”.
It is like a standardized “guide book”
Loaded on the main memory board.
This makes us feel as if CPU has a brain like humans.
It may first send hundreds of routine electric pulses
To different parts and gets only yes/no replies
If response is “yes” it switches one circuit .
If response is “no” it switches another circuit.
The so called intelligent work of CPU ,
It is all just a chain of switching.
Nothing magical in it.
It is all the intelligence of the man behind the machine.
Let us take example from real life,
To understand “micro instructions”.
You are sitting in a chair in your study.
You wish to take a book from the rack.
Your brain orders legs to make you stand
And alerts your eyes to closely coordinate.
Your legs start a small walk
And then stop at the rack.
The muscles of your hand are ordered to stretch
And the muscles in the fingers too
Then fingers grip the book
The book is securely held by the hand,
Then your legs walk back
And then your body comes to sitting posture
While your fingers grip the book
And place it in your lap to prepare you to study it.
All these are only a few of the micro operations.
There may be several dozens more.
The list of standard “micro instructions”
Are loaded by the “operating system”
The “operating system”, affectionately called OS
By all the folks using the computer,
Is only a part of the CPU .
The CPU issues endless sets of electric pulses
Which activate main memory, registers and the alu
This is the way the CPU commands other parts
It is really the chief switching engineer.