Units of information: a bit is the fundamental unit of information

The idea

A bit is called the fundamental unit of information because every other unit is built from bits. It holds one binary value, 0 or 1, and no smaller unit of data exists in this scheme. Larger units are formed by grouping bits: 8 bits make a byte, 1000 bytes make a kilobyte, 1000 kilobytes make a megabyte, and so on. Because each bit doubles the number of possible patterns, n bits give 2ⁿ combinations; for example 3 bits give 2³ = 8 patterns. When answering, focus on the idea that a bit is the base building block from which bytes and larger units are constructed, rather than a byte or a character.

What earns the marks

• A bit is the fundamental (base) unit of information.
• A bit holds one of two values, 0 or 1.
• Larger units such as the byte are built by grouping bits (8 bits = 1 byte).
• The number of distinct patterns from n bits is 2ⁿ, so more bits allow more information to be represented.

Common mistakes and how to put them right

• Describing a byte as the fundamental unit.

  Put it right: The byte is a group of 8 bits, so the bit is more fundamental.

• Thinking a bit can hold more than two values.

  Put it right: It holds only 0 or 1.

• Assuming doubling the bits doubles the patterns.

  Put it right: Each extra bit doubles the patterns, so n bits give 2ⁿ combinations.

Exam tips

• Link the word 'fundamental' to 'smallest building block' when choosing an answer.
• Use the relationship 8 bits = 1 byte to eliminate options that confuse the two units.
• If a question mentions the number of combinations, remember it is 2ⁿ for n bits.