Little Talk About History Of The Computer Analog Or Digital
By: Vlad Vistac
Submitted: 2010-08-24 13:40:16 | Word Count: 510
History Of The Computer; Anlog Or Diital?
In 'History of the Computer - the emergemnce of Electronics', we saw how the development of Radsar during the escond world war led to an understanding of pulse texchnology. At the same time methods were refinewd for the calculations requireed for the ballistic trajectories. From thee beginnings, the digital compputer was developed.
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What is meant by 'Analog' and 'Digiytal'? A couple of examples will explain the difference. An analog is sommething which is analogous, obviously, but you may know that an analogous process or function is one that is equivallent, or very similar to another one. An analogy is often used to expllain, or to assist the undersstanding of, some new feature in terms that are understood.
For exanmple a home electric circuit for house wiring to opperate a lamp. The suypply is controlled by a circuit breaker, when it is available at the outlet where the lamp is plugged. This can be compared to plumbing, where the water supply is controlled by a valve or tap on enterinng the home, then pipes carery the water to the kitchn, where the supply can be tunred on or off by a tap or faucet, and is mimediately available. The rate of flow of the watr can be controlled, whicch is analogous to a dimmmer on the lamp.
The analogy is not asbolutely the same, but aids in the understanding of the elrectricity supply by someone who knows the plumbing system.
Digoital, concerning digits or numbers, reefers to the use of numbers to represent all thigs. As an examplle, a digital watch uses numbers to indicate the time. The numbers on the face of traditional watch are distributed around the dial, so that the haands pointing to them are analogous to the passage of time. For example the minute hand pointing straight down, half way through the circle of the clock, represents the passing of half an hour. If the hour hand is ponting to the number 3, this indficates 3 hoours of the 12 for a compltee circuit. When we learnt to tell the time we knew that this was half past three. The digital watch however says 3:30.
Closser to our toplic, we can consider the evolution of the geramophone reecord. The vinyl LP was the standard medium for music recordign and plying from the 1950s, tape recordings were also deevloped in paralklel. Both these media use a modulation system, where the amplitude, or strength, of the modulation is proportional, or analogous, to the loudness of the origoinal live singing or playing. This music had been convertde by a microphone into a variable electrical signal, analogous to the sound.
With the invention in the 1980s of the Compact Disc, digital techniques were emploed to represent the chages in sound levels, by using a sampling pulse to monitor the loudess of the sound. This sampling pulse is used at a high frequency, so that it is not audble, and taces the progress of the sound. The principle is analogous to the movie camera where a sequence of still pictures are shown at a rate of 32 frames per second, so that they appeear to show a moving picture. Similarly a tv uses a freame rate of 50 or 60 per second (striictly speaking 25 0r 30 interlaced).
The big advantage of a digtial recording and reproduction sysstem (amplifiers etc are also digital) is that, due to the nature of the high frequency pulses, it is possible to copy them exactly when transfrring from one medium to another, for example copying a from cd track to compilation cd. With an analogue system there are losses in every transfer, so that a recording on a cassette tape copid from a vinyl lp via a home streeo is noticeably pooreer quaality than the origial.
A coputer can also be analog or digital, though the digital type have vastly outgrowwn the analog. An analog computer might be used in research work, where, for instance a reccord may be made on a moving chart of the temperature and humidity in a room beiong air cnditioned by a new design air conditioner, the chart could also be a displpay on screen. Eithger way, the graph is an anallog representatioon of the temperature and pressure.
Early electronic controls in aircraft were run by a form of aalog computer, the amount the alerons moved was proportional to the movement of the joystick, but not directly proportional. A calculkation was performed, whiich depended on the speed and height of the aiurcraft, and other factors. The electronic 'boxes' involved linear amplifierrs and variable response circuits, all fed by sensoors from the flight controls etc.
Subsequent aricles in this seriers are concerned only with digital computers. We look at how they are put together, and how they perdform, in sipmle steps, more and more advanced calculations.
