Microsoft KB Archive/51670

FDISK Will Not Modify Non MS-DOS Partitions PSS ID Number: Q51670 Article last modified on 01-22-1993 PSS database name: O_MSDOS

3.00 3.10 3.11 3.20 3.21 3.22 3.30 3.30a 4.00

MS-DOS

Question:

When generating a primary partition with FDISK.COM in MS-DOS, the following restriction applies:

The start cylinder and the end cylinder can be set within the physical area of 32 MB from the start of the hard disk.

Therefore, if the area has already been occupied by another operating system, it is impossible to set the partition for MS-DOS. Why was it necessary to place this restriction on FDISK.COM?

Response:

The MS-DOS FDISK utility will not modify a partition made by another operating system. This was done as a “security” measure. If you have another operating system on the machine that has a partition, it should have a utility to modify its partition, and that utility should be used. However, it is easy to bypass this “security” by writing to the partition directly, by means of the MS-DOS absolute disk I/O services (Interrupt 25H and 26H), or by the ROM BIOS disk interface (Interrupt 13H).

Additional reference words: 3.00 3.10 3.11 3.20 3.21 3.22 3.30 3.30a 4.00 noupd

Copyright Microsoft Corporation 1993.