Int 21/AX=2517h

AX = 2517h

Return:
CF clear
ES:EBX -> data buffer (protected mode address)
ECX -> data buffer (real mode address)
EDX = size of data buffer in bytes

Note: The data buffer's address changes after calls to AX=2512h and AX=252Ah

See Also: AX=2512h - AX=252Ah - AX=2530h