<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> <HTML> <HEAD> <META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9"> <TITLE>Large Disk HOWTO: Units</TITLE> <LINK HREF="Large-Disk-HOWTO-3.html" REL=next> <LINK HREF="Large-Disk-HOWTO-1.html" REL=previous> <LINK HREF="Large-Disk-HOWTO.html#toc2" REL=contents> </HEAD> <BODY> <A HREF="Large-Disk-HOWTO-3.html">Next</A> <A HREF="Large-Disk-HOWTO-1.html">Previous</A> <A HREF="Large-Disk-HOWTO.html#toc2">Contents</A> <HR> <H2><A NAME="units"></A> <A NAME="s2">2. Units</A></H2> <P> <!-- units!megabyte --> <!-- units!gigabyte --> A kilobyte (kB) is 1000 bytes. A megabyte (MB) is 1000 kB. A gigabyte (GB) is 1000 MB. A terabyte (TB) is 1000 GB. This is the <A HREF="http://physics.nist.gov/cuu/Units/prefixes.html">SI norm</A>. However, there are people that use 1 MB=1024000 bytes and talk about 1.44 MB floppies, and people who think that 1 MB=1048576 bytes. Here I follow the <A HREF="http://physics.nist.gov/cuu/Units/binary.html">recent standard</A> and write Ki, Mi, Gi, Ti for the binary units, so that these floppies are 1440 KiB (1.47 MB, 1.41 MiB), 1 MiB is 1048576 bytes (1.05 MB), 1 GiB is 1073741824 bytes (1.07 GB) and 1 TiB is 1099511627776 bytes (1.1 TB). <P>Quite correctly, the disk drive manufacturers follow the SI norm and use the decimal units. However, Linux kernel boot messages (for not-so-recent kernels) and some old fdisk-type programs use the symbols MB and GB for binary, or mixed binary-decimal units. So, before you think your disk is smaller than was promised when you bought it, compute first the actual size in decimal units (or just in bytes). <P>Concerning terminology and abbreviation for binary units, <A HREF="http://www-cs-staff.stanford.edu/~knuth/">Knuth</A> has an alternative <A HREF="http://www-cs-staff.stanford.edu/~knuth/news99.html">proposal</A>, namely to use KKB, MMB, GGB, TTB, PPB, EEB, ZZB, YYB and to call these <I>large kilobyte</I>, <I>large megabyte</I>, ... <I>large yottabyte</I>. He writes: `Notice that doubling the letter connotes both binary-ness and large-ness.' This is a good proposal - `large gigabyte' sounds better than `gibibyte'. For our purposes however the only important thing is to stress that a megabyte has precisely 1000000 bytes, and that some other term and abbreviation is required if you mean something else. <P> <HR> <A HREF="Large-Disk-HOWTO-3.html">Next</A> <A HREF="Large-Disk-HOWTO-1.html">Previous</A> <A HREF="Large-Disk-HOWTO.html#toc2">Contents</A> </BODY> </HTML>