Units of information: bit and byte

A computer stores and processes information using just two signs: 0 and 1. One such sign is called a bit, and it is the smallest unit of information. A single bit can show only two states, for example “on” and “off”.

8 bits together make 1 byte. One byte can hold, for example, one letter or digit typed on the keyboard. So the word “HELLO” takes up about 5 bytes.

For larger amounts we use bigger units: 1 kilobyte (KB) = 1024 bytes, 1 megabyte (MB) = 1024 KB, 1 gigabyte (GB) = 1024 MB and 1 terabyte (TB) = 1024 GB. A plain text document takes a few KB, a photo a few MB, and a film a few GB.

Knowing a file’s size is useful because you can work out in advance how many files will fit on a flash drive. For example, an 8 GB flash drive holds about 2000 photos of 4 MB each. The speed of downloading files from the internet is also measured in bits or bytes per second.

Key takeaways

• A bit is the smallest unit of information and can be 0 or 1.
• 1 byte = 8 bits.
• 1 KB = 1024 bytes, 1 MB = 1024 KB, 1 GB = 1024 MB.
• File size shows how much space the file takes in memory.