DOS2 File System

Boot Sector

Sectors from 1 to 3 contain boot record.

VTOC

Sector 360 contains Volume Table of Contens. Bytes $3 and $4 contain number of sectors available. At byte 10 there's Volume Bitmap. Each byte tells status of 8 sectors. When bit is on, sector is available.

Directory

Sectors 361 thru 368 contain the disk directory. Each sector holds eight file names.

Offset	Description
$00	Flags
	bit 0	Opened for output
	bit 5	File locked
	bit 6	File in use
	bit 7	File deleted
$01-$02	Number of sectors in file (little endian)
$03-$04	Starting sector of file (little endian)
$05-$0C	Filename (padded by spaces)
$0D-$0F	Extension (padded by spaces)

Sector 720 cannot be accessed with DOS 2.0

File sectors

First 125 bytes of sector contain data. Byte 126 contains file number in high six bits. Byte 127 and low two bits of byte 126 contain forward pointer. Byte 128 contains number of bytes in sector, highest bit flags end of file.