PC DOS 2.0 Observations/Flames
cdi!caf
DOS 1.1 (proper superset) and programs written for DOS 1.1 will run
on 2.0. (Bill Gates: Yes, absolutely! -PC World Vol 1 #1 p. 52)
In at least one instance, this is not true! In DOS 1.1, function 1Bh
returns a pointer to the current disc's file allocation table along
with other some information necessary to calculate the free blocks remaining.
(BTW, the DOS 1.1 documenation on this function was incorrect, indicating
two different items of information were returned in the same register -
See Fig. 1). In DOS 2.0, the pointer only points to the first byte of
that table - the rest has disappeared.
After spending an excessive amount of time debugging and printing listings
(The DOS debugger does not accept program symbols) I finally got the function
to work properly, only to find out that DOS 2.0 had a Flag Day for this
function.
Some other flames about DOS 2.0:
The disk buffers do not support read-ahead
or write-behind, even tho the IBM hardware is designed to allow this.
DOS 2.0 steps the floppies very noisily and seems to cause a disproportionate
number of bad sectors. It is necessary to turn verify ON in an autoexec.bat
file. However, once this is done, the date/time setting must be done in
that file and execution of batch files is still slow. Sorry, you can't
put those commands in the config file!
Even without disk read errors, DOS 2.0 has an unwelcome habit of corrupting
the file system by losing free blocks. It has become necessary to run
the disk checker program before any serious work to check on the integrity
of the file system.
The ANSI terminal emulation is minimal and lacks any editing functions
(insert/delete). As far as vi is concerned, it is not much better than
an ADM-3a simulation. In addition, some ANSI editing command puts the
emulator into some strange 40 column color mode.
The edlin editor remains a classic of cruftiness. It still crashes on
files without carriage returns. In the same article Bill Gates said:
"There's really a lot of dirty software on the market now; we'll have to
educate the developers about how to write better software." Judging by
DOS 2.0, edlin, and Microsoft Pascal, it would appear that Microsoft
will have to look outside their organization for suitable teachers.
By 2.12 things should be settled down, but in the meantime, Long live
Coherent, Marc and Unix (TM).
Chuck Forsberg