HP Laserjet 1536dnf MFP printer cancellation of fonts

Question

I have a technical question.  I developed my own word processing and printing programs starting with the original IBM and epson dot matrix printer and then the HP Laserjet printers.  Students a University of Pennsylvania and Princeton used my programs
to write their Ph. D. theses.  Now there are plenty of programs do to this but I have  kept my current.  Everything was fine until the printer listed in the title.  My program loads fonts in the printer.  The font # are 7000,7001,7002,7003,7004. 
I choose these numbers so as not to interfere with other fonts.  My program runs in DosBox and sends data to the printer by writing to the file TRASH789.PCL in the directory C:\SPOOL and the program printfile (downloaded from the internet) spools the
file to the printer.  When my program begins it sends the esc sequence that selects the fonts.  Also I set the  line feed to be 1/2 a line feed.  (My programs works like a typewriter and subscripts and superscripts are just a 1/2 space
up or down.)   On all other HP printers for say 20 years everything is fine but with the printer mentioned above my font selection and 1/2 line feed are canceled.  Various sequences of character will cause this to happen.  It is pretty
random.  One sequence I have isolated is below.
                    a3  a3  a3
The a's can be upper or lower case.  There can be other characters between then etc.  But if the first few lines that at printed contain these characters the fonts and 1/2 line spacing are canceled.  If you put a paragraph before the a3,a3,a3
it will not happen.  It the a3's occur at the top of a new page it will happen. 
   I have tried various things to fix the error like repeatedly telling the printer to select my fonts, or loading an empty rasher of graphics a the top of the page but nothing works.   Fortunately for 95% of what I print it is not a
problem.  I have work around solutions, making a PDF file using GHOSTPCL, or using another program that uses rasher graphics.  (I wrote this some years ago when I bought a DESKJET printer.  Now computers are so fast that the time delay with
the rasher graphics program is hardly  noticeable. 
      I realize that the number of people with my problems can be counted on one hand so there is no great motivation for fixing this problem but given the other problems with this printer (I have seen mentioned on the web) it seems
to me there may be a connection.  (I only bought this printer, scanner, fax, etc)  because I had a grant that was expiring and I wanted to spend the money.  My guess is that will all the functions of this printer, probably set up by different
groups of people, the printer has glitches.  As someone who has spent years on my own programs I know it can take months to figure them out.  My only hope is that maybe this might help someone.
   Thanks for your attention.

Answer 1

Hi treborpowers,
According to your description, you developped a program which runs in DosBox. When this program running, it sends request to DosBox, then DosBox sends request to Windows to call  Microsoft font 7000,7001,7002,7003, 7004, then Windows responds
this request, however, the program could not print the font in DosBox correctly. Right?
Since it is difficult to narrow down the issue is cause by Windows, in order to resolve this issue effectively, please get help from the professional forum about the programming language.
Thanks for your understanding!
Regards,
Lany Zhang