'===========================================================================
' Subject: VIDEO MEMORY SEGMENT              Date: 05-18-92 (21:02:00)    
' Author:  Matt Hart                         Code: QB, QBasic             
' Keys:    VIDEO,MEMORY,SEGMENT            Packet: GRAPHICS.ABC
'===========================================================================
' JG>   Is there a way that I can determine wether to use &HB000 or
' JG> &HB800 when doing stuff with the screen?

'A word (2 bytes) at 0000:0463h tells the port address of the CRT
'controller index register.  It will be 03B4h for monochrome and 03D4h
'for color, MSB last.

DEF SEG = 0
MonType$ = HEX$(PEEK(&H0464))+HEX$(PEEK(&H0463))
DEF SEG
SELECT CASE MonType$
     CASE "3D4"         ' Color
          StartSeg = &HB800
          NumBytes = 80*25*2
     CASE "3B4"         ' Monochrome
          StartSeg = &HB000
          NumBytes = 80*25*2
END SELECT

' JG>  And also, how do I save
' JG> and load screens with BSAVE and BLOAD? 

'For any screen, you save the number of bytes of the screen beginning at
'the segment and offset of the screen.  For text screens, this is:
     DEF SEG = StartSeg
     BSAVE "SCR.BIN",0,NumBytes
     DEF SEG

'Bload is the same:
     DEF SEG = StartSeg
     BLOAD "SCR.BIN",0
     DEF SEG