Invisible !BOOT

By Richard Dimond

Originally published in EUG #21

I was interested in Ross Little's idea for an invisible !BOOT file as I have found another method of doing this.

A disadvantage of Ross' idea is that since the window is reduced to a single space all the commands are printed at the same point on the screen and so the longer the file, the more visible this becomes - I have a !BOOT file which sets up several function keys plus other commands and it is quite noticeable.

My alternative method uses VDU 21 and VDU 6. The file should be set in the form:

         0C 15 0D
         Command (without CR character)
         0C 06 0D
This method does produce a truly invisible file but, after trying this out, I found it will only work for a !BOOT file of ONE command.

After experimenting with these, I thought of the idea of using VDU 17,0 to print in the background colour and VDU 17,1 at the end. This seemed to work but the cursor caused problems until I turned it off. Set up the !BOOT file in this form:

BOOT file in this form -

         11 00 17 01 00 00 00 00 00 00 00 00
         Commands as normal but without final CR
         11 01 0D
While the first and last byte values can be entered easiest with a sector editor as he suggest, if you have not got an editor, you can do this in the following way. Set up your file as normal without additions. Save this file and then *LOAD the file to &300C. This allows space for the twelve bytes from &3000. Enter these in this way:
         ?&3000=17   <RETURN>
         ?&3001=0    <RETURN>
         ?&3002=23   <RETURN>
         ?&3003=1    <RETURN>
         ?&3004=0    <RETURN>
         ?&300B=0    <RETURN>
Find the final CR character and replace this and the next two bytes in the same way with:
         ?<addr>  =17
This is easiest if you have a disassembler, eg TRACKER (EU Aug 1988) so that you can check the addresses and the final file before saving it.

The file should then be SAVEd by -

         *SAVE !BOOT 3000 +<length of file> 00000000 FFFFFFFF
When you have set up one file in this way, it is easy to make further files. *LOAD the made up file to &3000 and then *LOAD the new file to &300C. It is then only necessary to enter the final three bytes and save the file as above.

Some Further Comments

I would like to suggest letters for publication should, preferably, be written with addresses printed in a single line at the end of each letter. I know some members have done this (and I don't want to sound finicky) but the letters pages can seem untidy when it is not done. Also a neat line of *s or s at the end separating one letter from another may be a good idea too.

Regarding comments on editing out such things as 'I enclose cheque for...', only things for all to read should be put on disk. These things should be written as a short cover note.

Richard Dimond, EUG #21