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INT 0x21 - 0x48 - Allocate Memory


reg value descr
AH 0x48
BX number of memory paragraph requested


  • CF set if error
  • CF cleared if successful
reg descr
AX Segment address of allocated memory block (MCB + 1para)
error code if CF is set (see DOS Error Code)
BX size in paras of the largest block of memory available if CF set, and AX = 08 (Not Enough Mem)

Notes & Comments

  • returns segment address of allocated memory block AX:0000
  • each allocation requires a 16 byte overhead for the MCB
  • returns maximum block size available if error


back2root/ibm-pc-ms-dos/interrupts/int_21/int_21_48.txt · Dernière modification : 2023/01/16 17:54 de