Apple Partition Map (APM) is a partition scheme used to define the low-level organization of data on disks formatted for use with Macintosh computers. In computer engineering, hard disk drive partitioning is the creation of logical divisions upon a hard disk that allows one to apply operating system-specific logical formatting. ... The first Macintosh computer, introduced in 1984. ...

Apple disks are divided into blocks, with 512 bytes belonging to each block. The first block contains driver information. The actual partition map begins at block 1.

The Apple partition map is unusual in that it defines itself as one of the partitions on the disk. This means that every block on the disk (with the exception of the first block, block 0) belongs to a partition.

Some hybrid discs contain both an ISO 9660 primary volume descriptor and an Apple partition map, thus allowing the disc to work on different types of computer, including Apple systems. ISO 9660, a standard published by the International Organization for Standardization, defines a file system for CD-ROM media. ...

Intel-based Macintosh computers cannot boot from an APM disk, instead requiring the use of the GUID Partition Table (GPT). Vice versa: older Macs can not boot from GPT disks. GUID Partition Table (GPT) is a standard for the layout of the partition table on a physical hard disk. ... GPT is an acronym which stands for: GEC-Plessey Telecommuncations, the former name of Marconi Corporation Plc, a world leading telecommunications manufacturer, subsidiary of the General Electric Company Glutamic Pyruvic Transaminase, an enzyme which allows to determine the leaver function in a blood test Get Paid To (GPT) Website, a...

See also

• Structure of the Apple partition map, on Apple Developer Connection