Bits and Bytes

A byte is a sequence of eight bits. A bit is a unit that can be set either on or off, represented by 1 or 0. In other words, it’s a switch, like a light switch.

One byte can hold an unsigned value up to 255 (technically, as all zeros counts as a value, that makes 256 values).


Unit No. of bytes
Byte 1
Kilobyte (KB) 1000
Megabyte (MB 1,000,000
Gigabyte (GB) 1,000,000,000
Terabyte (TB) 1,000,000,000,000
Petabyte (PB) 1,000,000,000,000,000
Exabyte (EB) 1,000,000,000,000,000,000
Zettabyte (ZB) 1,000,000,000,000,000,000,000
Yottabyte (YB) 1,000,000,000,000,000,000,000,000


These units are used for measuring memory and data storage sizes. Early computers had very little memory (I once programmed an ICT 1301 with the equivalent of 4K of memory, and an IBM 1440 with 8K of RAM. I’m writing this on a PC with 32GB of RAM).

For operations, computers work with multi-bytes. For example, Windows 32-bit uses a four-byte unit for its instruction set. Windows 64-bit uses eight bytes.

Telecommunication Units

Instead of bytes, data transmission rates are usually shown in bits per second (bps). For example, a download speed may be rated as up to 100 Mbps (100,000,000 bits per second).

Mbps vs MBps

The lower and upper case ‘b’ is important. MBps refers to bytes, not bits. When you see speed ratings, check that letter. MBps is 8 times the size of Mbps (e.g. 100 Mbps = 12.5 MBps).


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