5 Jan
2005
5 Jan
'05
8:27 a.m.
> In the case of DOS 6.22, the message "Cannot
do binary reads from a
> device" is at offset 970F in COMMAND.COM
On Tue, 4 Jan 2005, Tom
Jennings wrote:
Sheesh, it only took them 10 years to declare it
impossible and
test for the error.
Well, ...
in DOS 4.00, it is at offset 7CCC. It may have been there since QDOS?
Although admittedly, I do not know whether earlier versions actually
included the test for the error to DISPLAY the message.
Perhaps some with older DOS currently installed could try:
COPY /B CON: filename
to see whether it notices?
But use of the built-in DOS device drivers in order to use COPY /B is NOT
the only way.
PC-DOS 3.30 (but probably NOT MS-DOS 3.30) has REC35.COM bundled
with DOS. That was mostly because IBM started using 3.5" drives on PS/2
WITHOUT usually having a 5.25" drive present, and needed a way to do
format conversion.
Or,...
you could write and debug a small bootstrap program for loading a binary
file through a port. [Left as an exercise for the reader]
The "operator" of the machine can then type it into DEBUG
or,...
Disassemble it into a text file of the source code with no labels,
comments, etc. insert an "A <crlf>" at the beginning, and add at the
end:
N filename <crlf>
R CX nnnn <crlf>
W <crlf>
Q <crlf>
For example:
A
JMP 106
DB 1A
DB 1A
DB 1A
DB 1A
MOV AH, 2
MOV DL, 42
INT 21
INT 20
N test.com
R CX E
W
Q
COPY that text file (yes, you can do it /A) into the machine, with a
filename on the order of TESTCODE.DAT
Have the "operator" of the machine type
DEBUG < TESTCODE.DAT <crlf>
It will produce a .COM file that CAN include ^Z characters.
One of the computer magazines (PC? PCWORLD?) used that briefly
as a way to distribute programs to their readers, some of whom
could not have managed without it. Another way they did it was
as DATA statements in a BASIC program.
The redirection into DEBUG has the advantage of not hiding the code
as thoroughly, and thus being less insulting to our intelligence.
--
Grumpy Ol' Fred cisin(a)xenosoft.com