A standard CD can hold just over a gigabyte (1,073,741,824 bytes) of data. However, the usable capacity is much lower and depends on the format applied (audio, computer data, etc.) when the CD is recorded. The reason for the lower usable capacity is that extra space is needed to store system data (table of contents, track information, and so on) and redundant information for error correction in case of scratches or manufacturing imperfections.
A full, 80-minute audio CD holds about 827 MB of audio data, while the same CD formatted for computer data would hold only 700 MB. The data-format CD has less usable capacity because computer data requires more space for error-correction information.
Prior to 2000, most CDs held 74 minutes of audio, or 650 MB of data. Improved manufacturing techniques have since increased capacity to 80 minutes/700 MB of data without affecting compatibility. Blank CDs are available in even larger capacities of up to 99 minutes, but these work only on the latest recorders and may be incompatible with many CD-ROM drives and audio CD players.