Bits and Bytes

Computers operate using a two digit number system known as the binary number system. The digits consist of 0's and 1's which represent on or off. The word bit is a shortening of the words "Binary digIT". Starting at zero and counting to ten the processor handles decimal numbers like this:

 0 =     0
 1 =     1
 2 =    10
 3 =    11
 4 =   100
 5 =   101
 6 =   110
 7 =   111
 8 =  1000
 9 =  1001
10 =  1010

Bits are almost always bundled together into 8-bit collections, called bytes. With 8 bits in a byte, you can represent 256 values ranging from 0 to 255, as shown here:

  0 = 00000000
  1 = 00000001
  2 = 00000010
   ...
254 = 11111110
255 = 11111111

The significance of bits and bytes relates directly to the processor and bus.  A 16-bit bus can handle 2 bytes of data at a time, where a 32-bit bus can handle twice as much data making it twice as fast.

A kilobit (abbreviated Kb) is a thousand (10³) bits. 1000 is equal to a binary number of 1111101000.   Although the bit is a unit of the binary number system, bits in data communications are discrete signal pulses and have historically been counted using the decimal number system. For example, 36.6 kilobits per second (Kbps) is 36,600 bits per second.

A kilobyte (abbreviated KB) is defined as 1,024 or (2¹⁰) two to the 10th power bytes. (2, 4, 8, 16, 32, 64, 128, 256, 512, 1,024) 1,024 is equal to a binary number of 10000000000. For example, a 1.38 megabyte (MB) formatted floppy disk is equal to 1,457,644 bytes or 1423.5 kilobytes (1,457,644 divided by 1,024). 

A megabyte (abbreviated MB) is 1,048,576 bytes in decimal notation or two to the 20th power bytes.  This is equal to a binary number of 100000000000000000000. Disk storage manufacturers define that a megabyte is 1,000,000 bytes in decimal notation. The BIOS recognizes 1,000,000 bytes as 976,563 bytes.

A gigabyte is two to the 30th power, or 1,073,741,824 in decimal notation.

A terabyte is 2 to the 40th power or approximately a thousand billion bytes.

A petabyte is 2 to the 50th power bytes or approximately a thousand terabytes.