| What is "digital"? |
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| A little overview of the word "digital" We hear the term "digital" so often that most of us do not even care to know what it really means. There are digital cameras, digital TVs, digital cable, digital this and digital that. So, let's discuss a little about what digital is from an engineer's perspective. I will attempt to explain in simplest terms possible, so as not to confuse you with technical terms. Broadly speaking, there are two types of signals - Analog and Digital. Analog signals are continuous type signals - meaning that they can have any imaginable value. On the other hand, digital signals are discrete signals, which means that they can have just two values, namely 0 or 1. Therefore, in digital systems information is stored in strings of 0's and 1's, called bits. Bit is a short form of Binary Digit. The number system employing just 0's and 1's is called the binary number system. In our every day life, we use decimal number system. Any number in decimal system can be converted to binary system and vice versa. For example, 13 in decimal system can be represented by 1101 in binary system. Now, the reasonable question would be - why use binary system to store information in digital systems? This is because it is easier to implement in physical terms. Suppose, you want to represent the number 13 in decimal in a physical way. Is it possible? Well, not so easily. How about representing 13 in binary (digital form) physically? Quite simple! For that, we can use a light bulb. Remember that 13 in decimal = 1101 in binary. So, we turn ON the bulb for one minute, and let it be ON for the next minute, and turn OFF during the third minute, and finally turn it back ON the fourth minute. Thus assuming that ON is 1 and OFF is 0, we have ON ON OFF ON = 1101. Wow! We represented the number 13 in binary (digital ) form! But, how can you store numbers in a computer? Well, these are done by turning ON or OFF the voltage so as to represent 1 or a 0 respectively by electronic components called transistors which act as very fast switches. There are millions of these transistors inside the microprocessor (e.g. Pentium 4) of a computer. They store and do calculations by being ON and OFF to represent the bits. All the calculations are done in binary system. Your digital camera stores your pictures in 1's and 0's. Likewise, your CD stores your music or pictures or other files in strings of 1's and 0's that are implemented by having microscopic pits on the surface of the CD that can be read by the laser. When the CD is read, if the laser encounters a pit it is a 0 , if there is no pit it is a 1. The bits in digital system can be represented by a number of physical ways. I hope this little explanation was helpful. |