Block Allocation Map

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In computer file systems, a block allocation map (BAM) is a data structure used to track disk blocks that are considered "allocated" or "free for writing." Very rapid file access was made possible by consulting a Block Allocation Map only when it absolutely had to (that is, when writing), and ignoring it when reading. This arguably made writing to the disk more time consuming than reading. Nonetheless, the difference between reading and writing was negligible when taking into account the time involved waiting for the medium to speed up, and synchronize into position. Regardless of whether the medium was a 5.25 inch floppy diskette, or a 3.5 inch 'semi-rigid' diskette, most of the time was spent waiting for the medium to get into place before reading or writing was suitable.