Bits, Bytes, Kilobytes, Megabytes & Gigabytes

Bit: We measure the information stored in a computer's memory and disk drives using bits. A bit is the smallest unit of measurement. Byte: 8 bits grouped together equal one byte. A byte is still a very small piece of information--one byte is equal to one character or one letter of the alphabet. Since a byte can only hold a very small piece of information, we often think in terms of kilobytes, megabytes, and gigabytes. Kilobyte (KB): Normally defined as 1,024 bytes, although many people round it to 1,000. An average word-processing document will consume about 100 kilobytes. Megabyte (MB): Defined as roughly 1,000 kilobytes or 1,000,000 bytes. While documents are usually measures in kilobytes, whole programs are measured in megabytes. A few years ago, when you purchased a new program at the store, it most often came on a floppy disk. Each floppy disk holds up to 1.44 megabytes of information. Programs were smaller then, so you would only need a few disks to hold the whole thing. These days, the size of programs have become much bigger, so that virtually all new programs come on CD-ROM. A CD-ROM can hold over 650 megabytes! Gigabyte (GB): Defined as roughly 1,000 megabytes. The increasing size of programs has resulted in larger hard drives. Hard drives used to be measured in megabytes -- a computer from 1988 might have had a 30-megabyte hard drive! Now, the average hard drive in a new computer is about 20 gigabytes. 1 Bit Smallest Unit 1 Byte 8 Bits 1 Kilobyte (KB) 1,000 Bytes 1 Megabyte (MG) 1,000 Kilobytes 1 Gigabyte (GB) 1,000 Megabytes Average Word Processing Document 20 KB Floppy Disk 1.44 MB (or 1440 KB) CD-ROM 650-800 MB (or 650,000–800,000 KB!) Hard Disk Size varies, but a new hard disk is typically 20 GB (or 20,000 MB or 20,000,000 KB!).