UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Gemini 80-Bus System

JohnBHanson · 19th Oct 2020, 9:52 pm

No I really do me 1bh 38h or in ascii ESC 8

The SVC Card uses ESC 1 through ESC 4 for the 4 screen modes it supports.

The emulator has extended that for ESC 1 through ESC 9 to give higher
resolutions. Because of the way cursor position is encoded the limit is 222 columns (Offset of 32, and cpm does not like outputing 0xff or 0xfe in some
versions).

Why the format.com program does is I do not know. On a real SVC card
it appears to do nothing. This code is followed by a 1ah which clears the
screen. This is also strange as it has just output a copyright message
before the ESC 8 ^Z sequence. So the program erases its own copyright
message.

On the emulator before the patch the ESC 8 sequence swallowed the next
character for the font height. which is why it looked like double line spaced.

Even worse - the format.com is coded so that the copyright message is not in
plain text, but is generated by subtracting a sequence from each character
in a string and outputing that.

Why a program would go to such lengths to hide its copyright message is
strange - first hide it coded in the binary and then erase it from the screen
as soon as it is output. The only thing I can think of is that this copyright
is in a library and the author of format wanted to hide the use of the library.

Very strange indeed.

If you want to experiment vpm/m supports the vdu command which can take decimal or hex arguments
eg
vdu 1ah
or
vdu 1bh 31h
etc

(There is also lpt which does the same for the printer).

Of course you can always use chr$(27) etc in basic.

can you please run vidreset which will make the SVC card report its software version number. Thanks. (I have 4.1 which is also
what my emulator reports).

19th Oct 2020, 9:52 pm	#447
JohnBHanson Heptode Join Date: Aug 2009 Location: Worthing, Sussex, UK. Posts: 662	Re: Gemini 80-Bus System No I really do me 1bh 38h or in ascii ESC 8 The SVC Card uses ESC 1 through ESC 4 for the 4 screen modes it supports. The emulator has extended that for ESC 1 through ESC 9 to give higher resolutions. Because of the way cursor position is encoded the limit is 222 columns (Offset of 32, and cpm does not like outputing 0xff or 0xfe in some versions). Why the format.com program does is I do not know. On a real SVC card it appears to do nothing. This code is followed by a 1ah which clears the screen. This is also strange as it has just output a copyright message before the ESC 8 ^Z sequence. So the program erases its own copyright message. On the emulator before the patch the ESC 8 sequence swallowed the next character for the font height. which is why it looked like double line spaced. Even worse - the format.com is coded so that the copyright message is not in plain text, but is generated by subtracting a sequence from each character in a string and outputing that. Why a program would go to such lengths to hide its copyright message is strange - first hide it coded in the binary and then erase it from the screen as soon as it is output. The only thing I can think of is that this copyright is in a library and the author of format wanted to hide the use of the library. Very strange indeed. If you want to experiment vpm/m supports the vdu command which can take decimal or hex arguments eg vdu 1ah or vdu 1bh 31h etc (There is also lpt which does the same for the printer). Of course you can always use chr$(27) etc in basic. can you please run vidreset which will make the SVC card report its software version number. Thanks. (I have 4.1 which is also what my emulator reports). Last edited by JohnBHanson; 19th Oct 2020 at 9:58 pm.