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Units in the Binary System:

Name Size (bits) Description
Bit 1 A single binary digit (0 or 1)
Nibble 4 A group of 4 bits
Byte 8 A group of 8 bits
Word 16 A group of 16 bits

For example: A computer image file is 512 bits in size. How many bytes does the image file use?

512 bits
Number of bytes =
8 bits per byte
= 64 bytes

So, the image file uses 64 bytes of storage.
The place value of each digit based on powers of 2 is shown below:

Position 4 3 2 1 0
Power of 2 2 4 2 3 2 2 2 1 2 0
Place Value 16 8 4 2 1

A binary number is usually written with a subscript 2 to show it is in base 2.

For example: (11001) 2
This shows the binary number 11001 with the base-2 notation, where 2 denotes that the number

is in the binary system.

RAPID RECALL Tick ( ) if you know this.

1. The decimal number system is the most commonly used number system in daily life.

2. A group of 16 bits is called a word.

OCTAL NUMBER SYSTEM

The octal number system is a base‑8 system that uses the digits 0–7. Each digit’s value depends on
its position, which is a power of 8. It is often used in computing because one octal digit represents
three binary digits, making binary numbers easier to read and write.
The place value of each digit based on powers of 8 is shown below:

Position 3 2 1 0

Power of 8 8 3 8 2 8 1 8 0
Place Value 512 64 8 1

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