Data arrangement and capacity

The data on a hard drive is arranged in the circular tracks. This is not like the spiral groove on an old fashioned phonograph disk. While that groove is long path, the tracks on a platter are individual circles. There are hundreds or thousands of tracks per radial inch of platter surface. Each circular track is broken into a number of arcs called as sectors. A cylinder is set of equal-radius tracks on all platters in drive. Tracks and sectors are set up on hard drive during the initial formatting process. There are data units called as clusters. These are units consisting of one to several sectors, depending on arrangement of data on platters. Figure given below is a face on view of a single hard disk platter, showing a track and one of its constituent sectors.

The average new computer hard drive data storage capacity gets doubles every year, and therefore increases by about 3 orders of magnitude per decade. At the end of 2000, during holiday computer-buying season, a new desktop machine had between 10 and 100 GB of hard drive capacity. By the end of year 2010, if trends continue, these figures will be around 1000 times greater—a range of 10 to 100 TB. Do petabyte and exabyte machines mention a few paragraphs ago seem out of this world, impossible? Extrapolate. Chances are good which you will live to see them.

When you buy a computer, whether it is a desktop, notebook, or portable unit, it will have a hard drive built in. The drive comes installed and formatted. Most new computers are sold with commonly used programs preinstalled on hard drive. Some computer users prefer to buy new computers with only operating system, by means of which programs run, installed; this frees up hard-drive space and gives user control over which programs to install.