CS-401 Computer Architecture Assembly Language Programming Lecture-35 DOS Services Secondary Storage

Lets revise the last lecture

Secondary storage

int 0x13 Disk Services 8 3 1 1 5 2 2 2 2 2 4 File name Extension 8 3 1 1 5 2 2 2 2 2 4 File name Creation Date Time Extension File Size Last Accessed Date Starting Cluster High Time Date Starting Cluster Low Flag Byte Reserved

int 0x13 Disk Services AH = 0*00 DL = Drive RETURN AH = Status CF = Clear on success CF =Set on error

int 0x13 Disk Services Read Sector to Memory AH = 0x02 AL = sector to read CH = cylinder number (low 8 bits) CL = sector number 1-63 (bits 0-5) cylinder number (high 2 bits) DH = head number DL = drive number ES:BX = data buffer Return CF = set on error AH = status AL = sectors transferred

int 0x13 Disk Services Write Disk Sector AH = 0x03 AL = sector to write CH = cylinder number (low 8 bits) CL = sector number 1-63 (bits 0-5) cylinder number (high 2 bits) DH = head number DL = drive number ES:BX = data buffer Return CF = set on error AH = status AL = sectors transferred

int 0x13 Disk Services Get Drive Parameters AH = 0x08 DL = drive number Return CF = set on error AH = status BL = drive type CH = maximum cylinder number (low 8 bits) CL = maximum cylinder number (high 2 bits) maximum sector number (bits 0-5) DH = maximum head number DL = number of drives

int 0x13 Disk Services Extended Read AH = 42h DL = drive number DS:SI = disk address packet (below) Return CF = set on error AH = status disk address packet

int 0x13 Disk Services Address Packet 1 1 2 4 8 Absolute Block 1 1 2 4 8 Absolute Block Number Transfer Blocks Blocks Size Reserved

int 0x13 Disk Services Extended Write AH = 43h AL = write flag DL = drive number DS:SI = disk address packet Return CF = set on error AH = status

Partition Table 446 16x4 2 MBR Partition Entries Signature

Partition Table Partition Entry 1 3 1 3 4 4 Status Starting CHS 1 3 1 3 4 4 Starting LBA partition Size of Starting CHS Ending CHS Status Partition Type