### Bits and Bytes

Because computers are made up of digital electronics, internally they respond to two kinds of electrical states: "on" or "off". These may actually be high or low voltage, positive and negative voltage, or some other combination. The key is that there are two conditions. We represent these with two numbers: 0 and 1, and the arithmetic that deals with these two states is called * binary arithmetic*.

Each 0 or 1 in the binary system is termed a bit (short for binary digit).

Strings of bits are used to represent numbers larger than 1 (much like combinations of digits are used to represent numbers larger than 9 in our decimal numbering system.

Bits in strings of eight are called bytes, and one byte usually represents a single character of data in the computer. It's a little used term, but you might be interested in knowing that a nibble is half a byte (usually 4 bits).

### Binary Numbers Explained

Let's look at the concept of binary numbers and bytes a little closer.

Think of binary numbers in terms of switches. With two switches you can represent up to four different numbers.

- 0 0 (OFF OFF) = Decimal 0
- 0 1 (OFF ON) = Decimal 1
- 1 0 (ON OFF) = Decimal 2
- 1 1 (ON ON) = Decimal 3

Study the above for a moment -- it brings out an important concept in computers. Do you see it?

Look at the decimal number versus the number of numbers. Two binary numbers gives you up to decimal 3, but there are four actual numbers. In our decimal system, we rarely think of the zero; with computers, zero is always thought of as a number.

Thus, a single bit represents 2 numbers, two bits give 4 numbers, three bits show 8 numbers, four bits represent 16 numbers, and so forth up to a byte, or eight bits, which represents 256 numbers. (Each added bit doubles the number of numbers.) But, while 8 bits represents 256 numbers the byte 11111111 equals decimal 255.

Just to show you the correspondence between binary and decimal numbers here is a table that runs down a few:

Binary numbers are formed just like decimal, except there are only two numbers to work with. Exhaust those two numbers and start over with the next position to the left filled with a "1".

When you are down to 111 you simply start the entire marked series over again with a 1 in front of it. Thus, every time you add a binary digit to the string you effectively double the number of total decimal numbers available for use.

Look at the table. One bit counts to two numbers, two bits count to four numbers, three bits to eight numbers, four bits to 16 numbers, five to 32, six to 64, seven to 128 and finally, one byte (8 bits) counts to 256 numbers.

- 8 bits = 1 byte
- 1024 Bytes = 1 Kilobyte
- 1000 Kilobytes = 1 Megabyte
- 1000 Megabytes = 1 Gigabyte
- 1000 Gigabytes = 1 Terabyte
- 1000 Terabytes = 1 Petabyte
- 1000 Petabytes = 1 Exabyte - In 2000, 3 exabytes of information was created
- 1000 Exabytes = 1 Zettabyte
- 1000 Zettabyte = 1 Zottabyte
- 1000 Zottabyte = 1 Brontobyte - that is a 1 followed by 27 zeroes

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