A program can read one or more sectors from a drive by using Absolute Disk Read (Interrupt 25h). The program must specify a drive number, a pointer to a buffer, a starting-sector number, and the number of sectors to be read. The function copies the specified sectors to a buffer.
A program can write one or more sectors to a drive by using Absolute Disk Write (Interrupt 26h). Programs that write directly to sectors must take care not to corrupt the data MS-DOS uses to maintain the file system. For information about this data, see Section 3.8.4, “Logical-Drive Contents.”
Absolute Disk Read and Absolute Disk Write read and write only nonhidden sectors. (Nonhidden sectors are numbered consecutively starting from zero.) This means that neither function can be used on sectors containing partition tables. For information about accessing all sectors of a logical drive, see Section 3.8.3, “Input-and-Output-Control Functions.”