ID Number: Q11276
3.20
MS-DOS
Problem:
Table 3.2 on Page 3-11 of the "Microsoft MS-DOS Programmer's
Reference" shipped with both the Alpha and Beta versions of MS-DOS
Version 3.20 shows some disk parameters for 80-track-per-side drives
that differ from versions of the parameters published in the past.
Have these parameters changed?
Response:
The parameters have not changed. Some of the information in the table
is incorrect. The errors are as follows:
1. The number of root directories for the single-sided 8-sector format
(the first column of numbers) and the single-sided 9-sector format
(the second column of numbers) should be 112, not 64 as listed in
the table.
2. The total number of sectors for the double-sided 9-sector format
(the fourth column of numbers) should be 1440, not 1640 as shown in
the table.
3. The Media Descriptor for the single-sided 9-sector format (the
second column of numbers) should be F8, not FB as shown in the
table.
4. The Media Descriptor for the double-sided 8-sector format (the
third column of numbers) should be FB, not F8 as shown in the
table.
The following is a corrected copy of the table:
Table 3.2 MS-DOS Standard Disk Formats
Disk Size 3.5 or 5.25 5.25
in inches
Tracks/side 80 80 80 80 80
WORD Bytes/
Sector 512 512 512 512 512
BYTE Sectors/
Allocation unit 2 2 2 2 1
WORD Reserved
Sectors 1 1 1 1 1
BYTE No. FATs 2 2 2 2 2
WORD Root Dir
Entries 112 112 112 112 224
WORD No. Sectors 640 720 1280 1440 2400
BYTE Media
Descriptor FA F8 FB F9 F9
WORD Sectors/
FAT 1 2 2 3 7
WORD Sectors/
Track 8 9 8 9 15
WORD No. Heads 1 1 2 2 2
WORD No. Hidden
Sectors 0 0 0 0 0