Date   : Tue, 14 Jan 1992 12:10:10 -0500
From   : Jay Sage <sage@ll.mit.edu>
Subject: beginning CP/M questions

Jon Lexau asked:

>>    - what exactly does the parameter block pointed to by the "seldsk"
>>        BIOS command contain?

This is too long a subject for me to answer here, but there are good books
that have all the details on this.  I recommend especially the following:

        Inside CP/M
        David E. Cortesi
        CBS College Publishing
        Holt, Rinehart and Winston
        ISBN: 0-03-059558-4
        QA76.6.C665

Cortesi wrote a number of books in this series on other operating systems,
including CP/M-Plus.

Briefly, the SELDSK call returns with HL pointing to what is called the Disk
Parameter Header (DPH).  The DPH is a table of further addresses of system
components, including that of the Disk Parameter Block (DPH).  The latter
tells how the logical disk is set up (number of sectors per track, size of
each extent, number of directory entries, number of system tracks, etc.

-- Jay Sage