Units

Computers store and process data using binary, but the size of data is measured using bits and bytes.

A bit is the smallest unit of data and can have a value of either 0 or 1. A group of 8 bits makes 1 byte. For larger amounts of data, AQA uses units based on multiples of 1000:

To convert between units, multiply when moving to a smaller unit and divide when moving to a larger unit.

For example, 3 GB = 3,000 MB, and 5 MB = 5,000 KB.

You may sometimes see 1024 used instead of 1000, because 1024 is a power of 2 and is convenient for binary-based measurements. You do not need to worry about this distinction for AQA GCSE Computer Science. Use 1000 for the conversions in this course, unless a question explicitly tells you to use a different conversion.

Remember – this is important:

• 8 bits = 1 byte
• 1,000 bytes = 1 KB
• 1,000 KB = 1 MB
• 1,000 MB = 1 GB
• 1,000 GB = 1 TB
• 1,000 TB = 1 PB