Computer's Little Tales -2

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Programmable memory

It became possible in the ancient calculators of 1940s

To solve long and tedious mathematical problems

In a systematic way and in a billionth of a second

Only after “programmable memory” was introduced.

By Dr von Neumann’s team

Even in the decades before Dr von Neumann’s time

The jumble of logic circuits did mathematics no doubt.

Addition and subtraction

Multiplication and division were all done

Using the “accumulator” logic.

But the human engineer had to sit

Before the jumble of logic circuits all time.

The human engineer had to send in numbers

In the 010101 code in a most tedious way .

Perhaps he was often confused with the maze of circuits

And endless rows of zeroes and ones.).


Dr von Neumann stepped in and dispensed with this tedious way.

He decided that just as a class room has a black board

For the teacher to write the detailed working steps

Of the tough algebra problems

A similar “memory board” is required right inside the computer

(Here the word “memory” means only a blackboard

And not the human brain’s capacity to remember.)

Dr Neumann loaded on the memory board

A series of “instructions” in standardized 010101code

For the CPU to follow to solve the problem.

The “instructions” also contained particulars

Of mathematical circuits to be operated by CPU

To make the arithmetic unit to do the toughest mathematics.

To start work the CPU obtained

Copy of each instruction from main memory

Through the computer’s super high ways

With eight / sixteen/twenty/forty lanes.

The very important parts called registers

Contained inside the CPU helped it

In a most efficient way to analyze each instruction

And do the switching of mathematical circuits

And to obtain numbers from the memory houses

And send them to alu to do the computation

By the accumulator principle which is very basic to the ALU.

To write a well knit group of instructions

(Called by people nowadays as a “computer program”)

Creation of the electronic “memory board”

Right inside computer was a must.

At that distant time of 1940s

The “memory board” was made of extremely tiny magnetic rings

Arranged in rows and columns perhaps on a plastic sheet

It was like a city of tens of thousands of tiny magnetic houses

Each magnetic house was made by interconnecting

Eight or sixteen chambers

To hold the eight or sixteen zeroes and ones.

The few dozen instructions together constituted

Working steps to solve a mathematical problem

And were collectively called a “computer program”

And this arrangement is called “programmable memory”

The memory board inside computer

Was known by technical name “main memory”

By using this principle the ALU could manage

The entire computing work without assistance of human engineer.

Since the human engineer’s instructions

Were already given in the program

His assistance was not much required.

He gave only an occasional nod or occasional frown

And toggled one or two keys on the key board and that was all

The CPU has to implement the “instructions”

One after the other to solve the “program”

The instructions are not like lines

From the poetic and dramatic works

OfShakespeare or Keats.

“A rose is a rose by whatever name you call it”

“A thing of beauty is a joy forever”

Such sentences can not be found

In “instructions” given to the CPU.

The instructions are like military commands.

A sample I give below

[Electric circuit for addition], [memory address of A],

[Memory address of B] ,[memory address ofK]

A and B are numbers to be added

And K is the answer after adding A and B

It is also a rigid rule that only the names

Of the memory houses are to be given

The parts called registers existing inside CPU

Get copies of the actual numbers a and b

From their respective memory locations

And send them to alu where the required mathematical circuit

For addition is already kept switched on .

All the “instructions” are thus processed

By the CPU one after another

With the help of “registers” (existing inside CPU)

Electric juice simply whirred

All the few dozen working steps (the instructions)

And the final answer for the entire program came

In just a millionth of a second.

. Under supervision of Dr von Neumann and his team

Programmable memoryperhaps on a small scale

and in an experimental waywas introduced

in the old giant size “valve based” electronic calculators

Which used tens of thousands of diode and triode valves

And which required huge air-conditioned halls.

The first experiments in programmable memory

Were done successfully with them.

The teacher writes the dozen working steps

Of an algebra problem on the blackboard

The human engineer’s “computer program”

Loaded on the “main memory board”

Is just similar to the algebra problem..

The human engineer too

Has to type his commands on key board

Only in strictly coded English

Approved by the association

Of electrical and electronic engineers.

Otherwise the CPU itself issues

A red lettered error message

To make the human being realize his/her mistake.


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