[comp.sys.ibm.pc] I am curious: cursor

cjdb@sphinx.uchicago.edu (Charles Blair) (02/21/88)

I wrote a simple routine to blank the cursor before pushing to DOS, as
follows: 

	mov	dx,3B4h		; 6845 address register
	mov	al,10		; cursor start
	out	dx,al
	mov	dx,3B5h		; base address of 6845 control data reg.
	mov	al,00101011b	; 01 in bits 6-5 makes cursor invisible
	out	dx,al

(The original code uses symbolic names for the values.)

I notice that this sometimes results in cursor loss at the DOS prompt.
I haven't been able to isolate the circumstances, but it seems to
happen consistently with IBM monochrome boards, and inconsistently
with Hercules GB112's. Can anyone think of possible causes?

I realize it is unecessary to blank the cursor before a push, but I
like to do it for a bit of finesse--if the EXEC call can't find
command.com, or whatever else it is I'm pushing, I don't like seeing
the cursor on the screen while I'm putting out the message to that
effect.

Thanks for any replies; e-mail responses preferred.


-- 
Bitnet:	  	 lib.cb@uchicago.bitnet
Internet:      lib.cb@chip.uchicago.edu
uucp:	  ..!ihnp4!gargoyle!sphinx!cjdb