Before any disks are able to be used, they must be formatted, although many users never have to do so, because they usually come from the store pre-formatted. Formatting wipes out any existing data, creates a file system to manage the new data, and divides the disk into tracks and sectors like a circular grid system. FAT32 is a common format that is compatible with most operating systems to organize the contents of disks into files and folders. Most Windows computers use the NTFS (New Technology File System), which provides additional security features. The latest versions of Mac OS X use the HFS+ (Hierarchical File System Plus).
The formatting process also includes an error checking procedure that examines each sector of the disk and ensures that it is physically sound. It also deletes all the data on the drive, so before you format a disk, you should make sure you have backup copies of anything on it that is important.
To format a disk in Windows, open My Computer, right-click on the appropriate drive, and select format from the available options.
To check a disk for errors in Windows, right-click the drive icon, click properties in that menu, click the Tools tab in the properties dialog box, and select the button Check Now.
On the disk there is a File Allocation Table (FAT) or index, which identifies the specific sectors and tracks where files are stored. When a disk is close to full capacity it may be forced to save a single file anywhere there is extra space, even if it has to break it up so that it is not continuous. When the computer has to search and find these individual parts of a file to place them back together it can take a long time to open the file. That is one reason why larger hard drives are, in general, faster. This is also why older, smaller hard drives used to require frequent defragmenting, a process which reorganizes data on the drive so data files are no longer broken up and scattered around the disk, thus helping the disk run more efficiently.
The difference between a music CD and a data CD is in the formatting. You can fit about 5 times as many mp3 music files on a data CD as songs on a music CD, but the data CD probably can’t be used in your car CD player, only on your computer.