Extended Write

Entry:
    AH = 43h
    AL
        bit 0 = 0 Write with verify off
              = 1 Write with verify on
        bits 7-1 = reserved, set to 0
    DL = Drive number
    DS:SI = Disk address packet
Exit:
    carry clear
        AH = 0
    carry set
        AH = error code

This function writes sectors from memory to disk

If write with verify is not supported, the BIOS rejects the request with (AH)=01h, CF=1. Function 48h can be used to detect whether write with verify is supported.

In the event of an error, the block_count field of the disk address packet is filled in with the number of blocks written before the error occurred.