terabyte

The terabyte is where the decimal-versus-binary confusion produces actual complaints. A drive sold as 1 TB holds one trillion bytes, exactly as advertised. Windows reports it as 931 GB — but what Windows is actually counting is gibibytes, 1,073,741,824 bytes each, while printing the letters GB.

Divide it out: $10^{12} / 1{,}073{,}741{,}824 = 931.3$. No bytes went missing. The manufacturer used the SI meaning of "tera", which is what the prefix has meant since 1960, and the operating system used a binary count with a decimal label.

The IEC settled this in 1998 by defining kibi, mebi, gibi and tebi for the binary powers, and thirty years on the labels still have not fully taken. Linux and macOS now mostly report honestly; Windows still prints GB for gibibytes. When it matters — capacity planning, backup sizing, quota configuration — the safe move is to work in bytes and convert once at the end.