1. Bits and Bytes
Key Revision Points

2. Bits Smallest unit of storage 1 bit
Can store either 1 or 0 only – used to represent an electrical signal being on/off
To store anything meaningful need to be combined in larger units

3. Bytes
Bits in modern computer grouped together in blocks of 8 (for historical reasons)
1 Byte = 8 Bits
1 Byte – any combination of eight 1s or 0s –
256 possible combinations (2 to the power of 8)

4. Nibble
Half a byte – geek humour!
1 Nibble = 4 bits

5. Larger Units (in size order)
Bit
Nibble
Byte
Kilobyte – exactly 1024 bytes (approx. 1 thousand bytes)
Megabyte – exactly bytes (approx. 1 million bytes or 1000 Kilobytes)
Gigabyte –exactly bytes (approx. 1 billion bytes or 1000 Megabytes)
Terabyte – exactly (approx. 1 trillion bytes or 1000 Gigabytes)