1) The table below states the formatted capacity of the 800K media:
800K Disk Specifications
------------------------
Bytes per Sector 512
Tracks per Side 80
Sectors per Track
Tracks 00-15 12
Tracks 16-31 11
Tracks 32-47 10
Tracks 48-63 9
Tracks 64-79 8
Sectors per Side 800
Sectors per Disk 1600
Bytes per Side 409600 (400K)
Bytes per Disk 819200 (800K)
2) The bottom of the disk is side 0; the top of the disk is side 1. The first
sector, block 0, is on track 0 of side 0. The last sector, block 1599,
is on track 79 of side 1.
3) A sector can be divided into four major sections. These are the header
sync field, the header field, the data sync field, and the data field.
These fields combined add up to 733.5 code bytes minimum.
Header Sync Field (6.25 bytes + sync overhead):
5 bit slip FF's minimum (FF,3F,CF,F3,FC,FF)
The header sync fields contain a pattern of ones and zeros that
synchronizes the hardware state machine with the data on the disk.
The header sync and headers field are written only when the disk is
formatted. The formatter should make this field as large as
possible, because this field buffers expansion of the previous
sector's data field due to speed variation of the drive.
Header Fields (11 bytes):
The header field identifies the sector. The sub-fields are:
D5 AA 96 address marks: this identifies the fields as a header field
Track encoded low 6 bits of track number
Sector encoded sector number
Side encoded high 2 bits of track number and side bit:
decoded bit 5=0 for side 0, 1 for side 1
decoded bit 0 is the high-order bit of the track number
decoded bits 1-4 are reserved and should be 0
Format encoded format specifications:
decoded bit 5=0 for single-sided formats
decoded bits 0-4 define format interleave:
standard 2:1 interleave formats have 2 in the field
Checksum checksum formed by exclusive 'or' in the track, sector
side, and format fields
DE AA bit slip marks: this identifies the end of the field
Off pad byte where the write electronics were turned off
Data Sync Field (6.25 bytes):
5 bit slip FF's (FF,3F,CF,F3,FC,FF)
The data sync field contains a pattern of ones and zeros that
synchronizes the state machine with the data on the disk. This field
is written whenever the data field is written.
Data Field (710 bytes):
The data field contains the actual data in the sector. The sub-fields
are:
D5 AA AD data marks: this identifies the field as a data field
Sector encoded sector number
Encoded Data 524 bytes encoded into 699 code bytes; the first 12 data
bytes are typically used as a sector tag by the operating
system, and the remaining 512 bytes are used for actual
data.
Checksum a 24-bit checksum encoded into 4 code byte
DE AA bit slip marks: this identifies the end of the field
Off pad byte where the write electronics were turned off