Monday, December 18

Revolution in Computer Design After dr John Von Neumann's Design And After Invention of Transistor

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The main ” thinking part” of  the modern computer is  called ” microprocessor”. It   is just  of the  size of a shirt button and is  encased in a postage stamp- size frame and  contains millions of submicroscopic  parts called transistors. These transistors can conduct electricity only in one direction and so can be used to switch on or switch off currents  a million times per second. Such a “superfast”  speed is required in modern computers.  Due to logic circuits(mathematical circuits) constructed with these transistors  a computer  can  solve  problems like 2+3=?,10-7=?, 4×5=?,30/8=? at the speed of a million problems in one second!  The newest  computers can do about a thousand million operations per second!

 The reason for such speed is this. Electric currents which flow at a speed of 300,000 kilometers per second do the mathematical work in the computers at such terrific speed. A computer’s brain  needs a superfast clock and a superfast switch. The transistor  is that switch   and is also used to assemble tiny ” clock circuits” which can produce extremely accurate clock signals. In coordination with the clock signal which  divides a second into a hundred  million tiny time units  all the mathematical  operations inside computer take place.  The step by step operations  going on in the  electronic parts inside computer fall in line with the pulses of the clock signals  like the movement of soldiers in a military drill( The pulses are produced at the rate of millions of pulses per second).  The transistor can work as a perfect switch because it alows current in one direction only  and stops current when it enters in reverse direction.

 Just as we use bricks to build  walls,rooms, canals,cupboards and  then entire multistoreyed houses we use” transistor” as the brick  to build all the” thinking parts” of the computer. First the parts called “logic gates”  using 20 or 30 transistors are built. . In each logic gate  a ” voltage”(current at a certain fixed level)  designated as ”  0 ” or ”  1 ”  level   can  stay for a long time. This is made possible  by making  the tiny electric  currents circle indefinitely inside the logic gates like water in a  whirlpool.  These “logic gates” are used to build   very fast data- forwarding parts called “registers”.The register contains a row of 8,16,32 or even 64 logic gates like police barracks. If  number of logic gates in a “register”  is large the calculating  power of computer also is large.  The primmary  unit for data storing has eight serial chambers . Millions of such data storage units exist in a  most important part called “main memory” inside the computer..”Main memory “is  like a big township with serial numbers for each data storage unit just like house numbers .                                                    

We have noted that the” register” is the smallest unit of data processing and exists in side the “processors”. The processors are the   real decision taking parts and are just big groups of registers .Each register  specalizes in processing a certain category of data  There are many processors inside the “microprocessor” each working like an office or bank .doing specialized service. the registers  dispose off incomoing and outgoing data  within a processor very fast. The register is  like a clerk  in a  bank or office.  In contrast a” processor” containing a few dozen registers  inside  is actually a specialized logic circuit.  It is is like a government office, bank.post office ,hospital,police station etc where a citizen can get a particular type of service. There is   chief   processor called the” microprocessor” overseeing work of all the other processors inside the computer.. This is  just like  a princpal  of a college guiding and controlling other proffessors.Thus we have one ” processor”  for mathematical work,  one for networking of  computers and one for  monitoring the  internal electric circuits of computer every second  etc.

. The   different processors  containing highly specialized registers  can do complcated  mathematical work, move data between different locations, process data for printing , rearrange words ,sentences and paragraphs in a page , adding color and editing color,searching for particular data in a big database etc.   Any of these works is done step by step extremely  accurately at terrific speed at the rate of  millions of steps per second. . The set of standardised  software instructions prepared by expert software enginners  in coded computer languages  are recorded on magnetic and optical discs.Such recorded discs are also sealed inside computer at time of manufacture. Such a bundle of discs sealed inside computer is called   “hard disk”.

These instructions written on discs in specially coded computer language run into tens of thousands of lines or even hundreds of thousands of lines.When we switch on the modern personal computer  and give a special command(i.e. coded language instruction) to it the software which we want is automatically copied from the hard disk to the “main memory”.   The “microprocessor” is the heart and brain of  the modern  computer. It is made of millions of transistors  and is actually a huge city of thousands of  smaller processors( the  decision making units) and millions of data storing units( like houses in a city where data are stored in unit sizes for further processing). This entire “city” exists on a single thin silicon chrystalof the size of a shirt button!

. The tiny transistors on the silicon crystal are  invisible to the naked eye and exist in three dimentional layers in geometrical patterns. Most  of them are interconnected by submicroscopic “wires” which are themselves not real wires but electronic designs also printed in neat geometrical patterns . The “inhabitants” in the rooms(logic gates) of these “memory houses” are the millions and billions of 0’s and 1’s.  (The 0’s and 1’s stay for only a limited time and new 0’s and 1’s come in their place in the next instant.) The “memory houses” too  like real houses have “house numbers” which are recognised by the computer programme .

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But let us think of the times which we can call the” stone age” of computers i.e the period of  the very first electronic computers ( built with  about twenty thousand hot filament diode valves in each calculator)  I used the word “stone age” with great regard and affection for these old electronic wonders which did the mathematical work at hitherto unheard of speeds..The first electronic computer like  ENIAC( 1946),  the EDSAC(1946),  UNIVAC(1951) were no doubt very efficiet giants but were  very   clumsy compared to the cute  little  personal computers  of today. The old computers  faltered every few hours  due to fusing of  dozens of  diodes every hour. Twenty four hour airconditioning was required.

As already mentioned the total  equipment  in each such computer required a dozen or more almirahs and required  a big airconditioned hall  for each computer. But they were magical machines which proved the scientific theory behind electronic computers and could do complicated mathematical calculations in  less than  thousandth of a second. There were hardly half a dozen such huge experimental installations each costing tens of millions of dollars.research on them was commissined only by the U.S.Defence department . The U.S.Army required almost  instantaneous mathematical data for sending american missiles in to the sky to attack incoming enemy rockets and destroy them in the skies.

( Of course radar signals were sent continuosly day and night every day to detect incoming enemy rockets by studying the reflected radio signals.Then the computer calculated within fraction of second the trjectory of incoming rocket,the required trajectory for the outgoing american rocket ,required quantity of fuel,engine speed etc  in thousandth of a second!)  

.The diode is the first  electronic devise which could be used as a very fast switching devise required in computers of first generation.. The diode could switch on or switch off small electric currents million times per second! It proved by its fast  switching power that electric currents  can be used to create fast mathematical machines. Each of these electronic giants perhaps looked like the famous  ” Time Machine” of H.G.Wells in science fiction with  hundreds of  switches,red/green/yellow indicator bulbs ,kilometers of  connecting wire,the  beep beep sounds  and blinking lights

. All the inputting of data(sending data to computer’s brain) was  perhaps done with the help of  rows of electric switches  and the outputting  (getting answers out of computer) was done perhaps by decoding with help of photo electric detectors The  output  data punched on  fast rotating paper tape .both the input and output were  in the form of long rows of 0’s and 1’s.  Only expert engineers and mathematicians could decode them. The  bizarre endless strings of “0”  and “1”s confused even the best electrical engineers and mathematicians sitting at the computer..

An interesting fact is that the calculating power of a pocket calculator of today is more than that of any of these ” first generation”  computers! The reason why they are classified as the first generation is that they used the “electronic parts” called  diodes (as in radio and tv)  and not the electro- mechanical parts like mechnical wheels  rotated by electric motors..

But still the computer was a very mysterious scientific device whose secrets were known only to big army generals,proffessors and seniormost engineers. Untill the great “transistor ” was invented and its great potentialities to replace the diode valves in computers were proved by engineers and scientist the computer did not  attract  the attention of ordinary citizens ,college and university students etc

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The invention of” transistor” was indeed a great event in history of computors.It is also the basic buiding block in radios,tvs,recording devices,radars etc.  The transistor is nothing but a tough solid semiconductor chrystal of the size of a sand particle.  After its electronic properties and great potentiality became known it almost entirely replaced the diode volve in computers,radios,tvs and all other electronic eqipment. The  lilliputian Transistor became  the ” brick” and basic building block for the assebly of logic circuits,registers and processors . It completely drove out the big hot filament diode valve in a few years. By 1955 thousands of transistors were connected into the electronic circuits of the computer and they performed exactly like the big hot filament diode valve .

The tiny transistor simply revolutionized the architecture of electronic computers. In the first days single individual transistors were used  to construct the logic circuits,registers and processors in computers just as in radios,tvs and other electronic eqipment.Individually and singly. the ”  transistors”  were  connected into the electric circuits  of computers by means of thin wires called “cat’s whiskers” firmly attached to the  transistor and outwardly visible.

Perhaps ten thousand to twenty thousand  big size individual transistors  were used in a computer with outwardly visible wire connections. These  clumsy fully transistorised computers are called the ” second generation computers”. These computers were also quite big  in size though not so big as the unwieldy” first generation” computers of 1950s made from diode valves     We can say that only since the second  generation  the  shape and  standard basic architecture of  the computer became clear and its  great potentiaities   were properly understood. The second generation machine soon attracted the attention of engineers,technicians,mathematicians,  businessmen etc. But it was a clumsy machine by modern standards.

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 At about  1965  other extremely significant and path breaking developments took place in transistor technology.  Entire sets of  transistors along with the electrical parts called  resistances and capacitors  required in every electronic eqipment like radio, tv  and computer were “grown” on a single thin silicon crystal  by chemical and heating processes.Even the electric leads (in place of wire connections) were also “grown” on the silicon crystal base.  This technology is called “integrated circuit” technology. In the begining only a group of ten or twenty transistors arranged in a particular logic circuit and its  electric connections ,resistances,capacitors etc were   ” grown” on a single silicon chip. Such basic units were used to assemble registers,processors etc.

Later  far  bigger sized “integrated circuits ”  were grown on a single silicon crystal  successfully   The computers built using  the “integrated circuits”  were very sturdy and also quite small  resembling a  big size tv set. Such computers consumed only low quantities of electrical energy because like telephones they worked on low voltages like 10 volts and 15 volts.They did not heat up during functioning and worked for hours together without any break . What is more , the computing speed and memory capacity increased many times and cost decreased .( because silicon chrystals were very cheap  compared to the hot filament diodes.) . The  technologies  of today can “grow”  upto twenty million  transistors on a sigle silicon chip. This resulted in  increasing the processing capacity hundreds of thousands of times. The new technology showed the potential of a modern transistor based computer.

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The great American scientist and mathematicia  Dr.John  Von Neumann  can be called father of modern computer. It was he  who proposed in 1946 construction of “stored program” electronic calculators and proposed a detailed internal architecture consisting of a “main memory” from  which data and instructions(formulas) would go to the registers inside the main processor and necessory mathematical circuits would be switched on and answers  flowed back to a section of main memory.  Every  register played a predesignated role inside the processor. The main processor  processed  data only as per the instruction set loaded by the programmer on the main memory

.After  the incorporation of a seperate part called “main memory” in  the giant electronic calculators of those days,we can say that the modern electronic computer was born. But the entire computer was constructed only with hot filament diode valves. It is wonderful to note that even the latest computers  still  follow the  basic architecture proposed byDr.Von Newmann. The world should be greatly indebted to him. The “main memory” in computer is  a data storing part like a city with millions of buildings and neat streets with each house being alloted a specific house number.  It is also like the black board in a class room used by the maths teacher  to write the formulas,the maths problem,working steps and the answer. When the next group of students come  the teacher  rubs away all that is written for the previous group  on the black board. Then he writes new formula,new problem,new working steps and answer. When this group goes he repeats the procedure for next group.

 In the class room the mathematics problem has generally about ten steps in its working. But in the tough mathematical problems solved by computers there wiill be hundreds or even thousands of working steps. They are collectively called the “stored program” and are written on the part called”main memory” by computer engineers( by typing in data through punched tape or keyboard )in a coded form . The code is in the form of  rows and rows of  0’s and 1’s   and can be understood only by the computer engineer and the ” processors” of the computer. 

To understand the meaning of ‘stored program” computer we should first understand  the difference between a computer and a tv (or radio). In radio/TV the far away   programmes are recieved through  radio waves from the far away  radio/TV station.  At the very instant after we hear/see those programmes   the signals disappear from radio/TV  without trace just as water poured into a bucket with a gaping hole flows  out from bottom( as soon water is poured at top).  The data of the just concluded programme disappears from the radio or TV .  But in Von Neumann model  of the computer,   the” computer programme” which is a set of   a few hundreds  mathematical steps  (just like working steps which  the teacher writes on the black board )is recorded in advance  on the black board  called “main memory” .

The” main memory” can also be compared to the white paper  note book which the student uses to write down the steps dictated by the teacher. The student  can read the matter even   a few  months after it is written as it is recorded. In ordinary language the word memory means our brain’s remembering capacity. But incomputer matters the word “memory” represents  ” the device like black board , white paper note book,  we use to record any matter  permanantly  so that we can utilise that  data  at a later time “.

Similarly we can also read old data in computer  even days or months latter by  cheking the part called “main memory” .  However in modern computers all the data lying on “main memory” is copied to files in the hard disk by giving the “save” command on key board. “Save” means “preserve permenantly”.. The main memory is automatically ” wiped clean” when  we switch off the computer.  Next time when we switch on the computer we can give command to computer to bring a particular file to main memory.

   “The commanding and controling part in computer”(the CPU) studies whatever”instructions” from human operator/engineer are recieved (as found on the part called “main memory”) and processes them. The “instructions “given by an engineer to computer are in a  highly coded computer language like “c” or “c++”  with not even an extra comma or full stop permitted. They are actually a kind of mathematical code with “reserved words” which can acess and activate huge central electric circuits inside computer. We can bring  hundreds or even thousands of commands or instructions onto the main memory  from the files in the hard disc  by giving proper commands

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   As already said even before arrival of first generation computers there were a few dozen electricity based calculating machines. They also performed well but could not store any data (like radio/tv )as explained above. What was the idea behind construction of  those old calculators which existed before the first generation machines? Many electrical engineers and mathematicians had  for many decades pursued  an exciting idea. Electricity travels in wires at speeds of 200,000 kilometers per second or more. Electricity has two states i.e “switch on current” and  “switch off current”.  Let us represent “switch on state ” of an electric bulb as “1” and” switch of state” as “0”. 

The electric engineers and mathematicians argued  as follows . Suppose  we  represent  all numbers in a 8-digit code  having different combinations of  “1”s  or “0”s  only.  We have eight independant parallel electric circuits in which only two specified levels of current can flow and these levels are represented as “1′ or “0”. All the eight currents (in only two varieties either “0” or “1”) are controlled by a single switch i.e.  they start or stop at the same moment . Then can we   make numbers” flow” through electric wires  by giving each number a 8-digit code like “11010101”?.

Such a combination of eight 0’s and 1’s will circulate through the parallel paths seperately but will together represent a number like   0,1,2,3,4,…..9.. If numbers are sent through such binary code (i.e. the 0 and 1 code) and special mathematical circuits are developed  then electricity can be made to solve mathematical problems at speed of flow of electrons through wires i.e. at about 200,000 kms per second. The answer after about six,seven decades of research was the eletronic calculators invented in 1950s.

 (A)Let us consider an example of how a computer  makes mathematical calculations.

Example 4×1000 =?

It is solved by computer as 4+4+4+4+4+…1000 times.

it is done as follows 

4+4=8

8+4=12…

12+4=16..and so on for 1000times. At the end it looks as below.

 3988+4=3992

3992+4=3996

3996+4=4000

For us it is a tedious way but for computer it is  a most easy thing. It can do million sums like   8+4=12 in just one second.

(B)  we can  represet numbers(1,2,3,4…etc)  by different combinations of “1” and “0” taken in a  groups of eight “1” or “0” symbols

ex:    0000 0001=1      

        0000 0010=2

         0000 0100=4

         0000 1011=11 and so on

(C)  we can also suggest a code to represent alphabets like a,b,c,d etc or symbols like ?,+, %,& etc.To represent alphabets add two more “0” or “1” s to each eight group as a specially coded prefix( indicating a special electric circuit.)

ex:    01  0000 0000=a

         01  0000 0010=b

         01  0000 0100=c   and so on

(D)To represent ” special symbols ”  we can add another type suffix(i.e.”10″ instead of “01”)

ex:  10 0000 0001 =”+ ”

      10 0000 0010=” ?”

       10 0000 0100=”%” and so on       

(note: The examples are hypothetical but computers follow only very similar logic)

The first computers  needed only binary codes(i.e. the 0,1 code)  for numbers.They did not use alphabets (a,,b,c,d .etc)or symbols like( +,-, ?.) They had only electric circuits  for  doing addition,subtraction,multiplication.division etc . They had no need for alphabets and special symbols. We should clearly understand that the first computers were only very fast  mathematical  calculators having no need for alphabets and any other symbols. Only later for electronic printing of textual data by computers and not for any mathematical work the above sbinary codes were standardized.

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 Modern computers  are thousands of   times more powerful than the 1st generation  “stored programs ” computers invented by Dr John Von Neumann. This is because the processor speed , memory capacity,data access speed and data transfer speed all have increased many fold after the silicon chip containing millions of transistors came into use. Modern computers can perform many other tasks like preparing engineering drawings for designing cars,airplanes,ships etc, composing and printing  pages of matter,composing and printing text books, taking a photo or vedeo and printing it instantly, playing films from recorded CDs  etc.Computers connected to Internet can upload or download printed pages, printed text books, photograpphs, audio and vedeo,lengthy  cinema films etc.

 What are calculators?The pocket calculator everbody now uses is   a most advanced  Von Neumann  model computer  doing only mathematical work. A big computer  of  1940s costed millions of dollars but the small calculator avalable with high scool students  costs only a few dollars and has more calculating power!

.What is a cell phone? It is  a very powerful network computer as powerful as personal computers used in banks and offices. It can connect to any cell phone or digital land phone or networked computer any where in world  in a second with the help of  very powerful softwares like TCP/IP.

What is a robot? It is one of the ultimate marvels  in “stored program” computers. It would take  at least three or four  years to load its brain with whole dictionaries,encyclopedias,formulas of mathematics and engineering.Some modern robots can  pour tea into cups,walk a few feet and serve the tea most carefully with out spilling a drop. Some can fight duels on a stage  falling,rising and balancing their bodies and fight.as long as you want.Some dance to recorded music which a guest from outside brings . Some can recieve guests,greet people and give answers . Robots have intelligence of two year old children ,

Note: this essay is only for lay persons who do not know the basics of computer. so the statistical data is also  given in a rough way  without going to  extremities of  accuracy.                                                                    ****************************  

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