In computer science, a memory map is a structure of data (which usually resides in memory itself) that indicates how memory is laid out. The term "memory map" has different meanings in different contexts.

PC BIOS memory map

BIOS for the IBM Personal Computer and compatibles provides a set of routines that can be used by operating system or applications to get the memory layout. Some of the available routines are: BIOS Function: INT 0x15, AX=0xE801: This BIOS interrupt call is used to get the memory size for 64MB+ configurations. It is supported by AMI BIOSses dated August 23, 1994 or later. The caller sets AX to 0xE801 then executes int 0x15. If some error has happened, the routine returns with CF (Carry Flag) set to 1. If no error, the routine returns with CF clear and the state of registers is described as following: BIOS Function: INT 0x15, AX=0xE820 - GET SYSTEM MEMORY MAP: Input: SMAP buffer structure: How used: The operating system shall allocate an SMAP buffer in memory (20 bytes buffer). Then set registers as specified in "Input" table. On first call, EBX should be set to 0. Next step is to call INT 0x15. If no error, the interrupt call returns with CF clear and the buffer filled with data representing first region of the memory map. EBX is updated by BIOS so that when the OS calls the routine again, The next region is returned in the buffer. BIOS sets EBX to zero if all done.