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=?, 4x5=?,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 t ownship 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 " processo r" 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 4x1000 =?
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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