DIGITAL COMPUTER TECHNIQUES & PRINCIPLES

just what our digital computers are they superhuman machines that can solve any kind of problem no not any kind are they man-made monsters that perform mathematical miracles and millionths of a second no nothing miraculous at all nor monstrous are they electronic brains that can do man's thinking for him well they can do some of it and be big and quick about it too large computers can remember and keep tab on millions of bits of data and fetch and use any of them in a fraction of a moment and computers operate faster than well how many human beings using desk calculators would you say a hundred a thousand more than that yes five hundred thousand yet as complicated as they might appear digital computers are basically simple a collection of ideas and principles that are not at all difficult to understand nor are they very new here is the first computer man ever used it was the first digital computer indeed the word digit comes from the Latin word for finger used in counting then digits became numbers to keep track of numbers or to count higher man used stones we still use the Latin word for stone calculus and the first calculating device may have looked like this with it you could count your sheep your children your prayers in fact the anglo-saxon word bead meant prayer when man put up his counting beads like this he grouped them like the digits of his hand with the extra beads counting the number of fives the abacus used by all civilizations of antiquity is still a widely used counting or accounting device 350 years ago a Scottish scholar preacher and mathematician named John Napier invented these ivory calculating bones as they were called this is one of the original sets they were used for multiplication a few years later the French genius Blaise Pascal invented and built the world's first mechanical adding machines this is one of them made in the 1640s Pascal's achievement lay in the gear mechanism which automatically took care of carryovers for example six plus nine as the one carried over to the next place also in the early 1600s an Englishman William authorid put together two logarithmic scales like these and made the form of slide-rule we use today an indispensable three hundred-year-old tool in every area of Defense science engineering and business progress depends on the availability of fast accurate methods of calculation they have enabled us to take giant steps forward in power in control in design in processing and in research our seven-league boots are our calculating machines and they come in many styles in some the action is entirely mechanical using levers linkages gears and ratchets to perform the calculating operations the method used here is digital that is the machine works with digits actual numbers in this type of calculator or computer the action is electromechanical it makes use of servo motors potentiometers cams friction drives and similar devices they are moved or set so that shaft positions voltages angles lengths and other physical quantities represent the numbers involved in the calculations since equivalence or analogs of numbers are used rather than numbers as such these types of machines are called analog computers in this type of computer the action is entirely electronic and completely automatic the working parts are transistors vacuum tubes magnetic devices and other electronic components the machine works with actual numbers and is therefore a digital computer this film is concerned with this type of computer and its purpose is to present a general introduction to the subject the computer process is a logical one and is easy to follow it begins with the problem which may concern virtually any subject that can be treated mathematically determining the path and I'm positions of an orbiting satellite computing payrolls for thousands of employees equalizing the load in a power transmission network controlling airport traffic forecasting the weather or designing a missile and it's system whatever it is you have the problem and you have data or information which the computer will process to arrive at a solution to do this processing the computer needs instructions so you write a program a complete detailed list of every operation the computer must perform to solve the problem then the completed program that is the instructions and the data the information to be worked on are both prepared for insertion in the computer by transferring them to an input medium this may be punched cards punched paper tape or magnetic tape for automatic insertion or a typewriter for manual inputs the medium carries the inputs in code language acceptable to the computer the computer first stores the program and the data and then processes the data as directed by the program the results of the computers work are transferred to an output medium such as punched cards punched tape or magnetic tape that presents the data in computer language or the media may be a printer that presents the output in readable form thus the solution is the completion of the process that began with the problem and the data these elements are pertinent to all automatic digital computer systems now let us look at the functions performed by the computer it has the ability to add which it does by counting to subtract by counting in Reverse and to multiply and divide operations that are based on addition and subtraction these are the computers arithmetic operations it can also perform what are known as logical operations it can compare one number with another it can sort numbers into a particular order it can find a specific number and it can do such things as distinguish between positive and negative signs thus the computer can make simple decisions or choices but only as instructed it operates on the basis of simplicity in the mathematical functions performed multiplicity in the number of times these may be done and speed that is fantastic it is accomplished electronically by means of transistors semiconductor diodes and vacuum tubes such devices have a two-state characteristic the ability to switch from one state to the other off on cut off conduct low voltage high voltage and so on switching in this manner in millions of seconds microseconds this two-state characteristic is the foundation of electronic digital computer operation however these two states and the ten digits of our decimal number system are not compatible cannot be easily matched fortunately there is a number system that is compatible it is based on only two digits 0 and 1 this is the binary number system by meaning to you'll hear a great deal of it in connection with digital computers these two digits can be used to represent any number we wish you'll find a full explanation of it in a later film for now let's accept the fact that a two-state device such as a lamp or a diode or a transistor can be used to count in the binary system off can be considered binary zero on binary one let's add another component now there are more possibilities 0 0 0 1 1 0 & 1 1 3 will give us more combinations add more lights and even more combinations are possible since the computers language is binary we must feed data to it in binary form take these binary ones they can be represented by holes punched in a card at keyed locations unpunched locations represent binary zeros we can use cards like these as an input medium or an output medium special coding enables us to represent letters of the alphabet punctuation marks and other symbols a single card has approximately a thousand locations for such bits of information bits is an abbreviation of binary digits the data recorded on the card are read by metal fingers or brushes that make electrical contacts through the holes and no contacts where there are no holes reading may also be done by using light beams and photocells paper tape is a similar carrier of information magnetic tape which has an iron oxide coating is still another vehicle for information small areas are magnetized shown here symbolically in one direction to represent binary zero and in the other to represent binary one thus problem data and program instructions carried by the tape or whatever input median is used enter the computer in the form of a binary code the computer is part of a system that includes input and output devices the input device is a data reader that converts the tape or card information into coded pulses of electricity high and low voltages that represent binary ones and binary zeros the computer contains storage control and arithmetic sections the storage section sometimes referred to as the memory contains elements that receive and store the problem data and the instructions the control section directs all computer operations essentially control is a timing and gating system for transferring data it controls input takes each instruction from storage and interprets it sets up the arithmetic section to do the mathematical or logical operations required releases the problem data to the arithmetic section and routes the rows to storage when the problem has been worked out control routes the result to the output device this device transfers the results to an output medium tape cards printed form or visual display this then is the general scheme of operation of an automatic digital computer or giant in subsequent films you will get to know the special meanings of such terms as word logic register clock and or and flip flop the automatic digital computer is a remarkable tool in its many forms and sizes that can do almost anything but only at man's bidding it will never duplicate the achievements of the human mind for the computer has no initiative no imagination no spirit yet it is opening new fields of thought and work and new goals for the human race man has made many tools that have multiplied the power of his hands here is one that multiplies the power of his mind [Music]