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A byte is eight bits, or eight binary digits. But what does this actually mean? Well, lets us look at decimal arithmatic for an example. If we take a six digit decimal number it can represent any number from 000,000 to 999,999. That is: Every single number less than one million.
So what does this mean for binary arithmatic? More specifically, what does it mean for the definition of one byte. Well, a byte can represent every single number between 00000000 and 11111111.
But what does the binary number 11111111 actually represent? Well a binary number of 1 is 1. A binary number of 10 is 2. A binary number of 100 is 4 A binary number of 1000 is 8 A binary number of 10000 is 16 A binary number of 100000 is 32 A binary number of 100 is 4 A binary number of 1000000 is 64 A binary number of 10000000 is 128 Therefore a binary number of 11111111 is: 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255.
So a byte can represent any decimal number between 0 and 255. Therefore if one wishes to be perverse (and computer people are very perverse people) one could say that a byte can represent 256 different numbers, one of which, is zero.
That is one way of looking at a byte. However, there is another way of looking at it. A byte can also be defined as the smallest piece of information, which can be stored on a computer. Now actually, that is nonsense. Quite obviously, the smallest piece of information is a bit. However, a bit is so small it is virtually useless. Therefore bits are always grouped together in bytes, because a byte is the smallest piece of information which is actually of any use.
Now for this information to be really useful, a byte has to be capable of representing more than a number. It has to be capable of representing an alpha-numeric character set. It also has to be capable of being used to represent every single instruction a computer is able to understand.
A computer's memory is composed of millions of objects called registers. Every register is composed of two or more bytes. For different computers, the number of bytes used to make a register varies. The number of bytes that make up a computer's register is referred to as the computer's word length. It is this word length which is referred to when one talks of a 16 bit computer, a 32 bit computer or a 64 bit computer. In other words a 16 bit computer has a 2 byte word length. A 32 bit computer has a 4 byte word length and a 64 bit computer has a 8 byte word length.
Everybody knows what one normally means when one talks of a "Word" However, in the computer world a "Word" has another meaning. In computer speak a "Word" is a collection of bytes.
So we now know what a computer programmer or a computer engineer means when he or she talks about a word. Being a normal human being, they might be using the word in the same way as the rest of us. Alternatively, they might be talking about a collection of bytes. How big is that collction of bytes? Well, that all depends. Depends on what? It depends on the word length of the computer they are talking about. If they are talking about a 16 bit computer, they will be talking about a two byte word. If they are talking about a 32 bit computer, they will be talking about a four byte word. If they are talking about a 64 bit computer, they will be talking about a eight byte word.