◄Summary► ◄Up► ◄Contents► ◄Index► ◄Back► ──────────────────────────────────────────────────────────────────────────── All registers except the segment registers may be destroyed. When this function returns, the CPU flags originally pushed on the stack by the Int 25h instruction are still on the stack. The stack must be cleared by a POPF or ADD SP,2 to prevent uncontrolled stack growth and to make accessible any other values that were pushed on the stack before the call to Int 25h. Logical sector numbers are obtained by numbering each disk sector sequentially from track 0, head 0, sector 1, and continuing until the last sector on the disk is counted. The head number is incremented before the track number. Logically adjacent sectors may not be physically adjacent due to interleaving that occurs at the device-driver level for some disk types. The error code is interpreted as follows: The lower byte (AL) is the same error code that is returned in the lower byte of DI when an Int 24h is issued. The upper byte (AH) contains: Error Description 80h If attachment failed to respond 40h If seek operation failed 20h If controller failed 10h Data error (bad CRC) 08h If direct memory access (DMA) failed 04h If requested sector not found 02h If bad address mark 01h If bad command [Version 4.0+] When accessing partitions larger than 32 megabytes under MS-DOS version 4.0, this function uses a parameter block with the following format: Bytes Description 00h-03h 32-bit sector number 04h-05h Number of sectors to read 06h-07h Offset of buffer 08h-09h Segment of buffer -♦-