Date: Mon, 18 Mar 1996 13:01:54 -0500 (EST) From: Christopher A Triebel To: "A.Appleyard" Cc: DJGPP AT delorie DOT com Subject: Re: Graphics modes In-Reply-To: <6020C27A13@fs2.mt.umist.ac.uk> Message-Id: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII On Mon, 18 Mar 1996, A.Appleyard wrote: > Does djgpp v2 still carry around a load of graphics drivers? Or does the > (first graphics call in each run of a djgpp program) call some such interrupt > as `AX=0x4f01, int10' to find what modes it has, and thus decide what DOS or > VESA screen mode to use to represent each of the 9 djgpp screen modes? > djgpp screen mode 7 is described as "biggest non-interlaced graphics". What > is "non-interlaced" graphics? Why is non-interlacing-ness relevant? How do I > find via `AX=0x4f01, int10' whether any particular screen mode is > non-interlacing? > This is my first ever response to a news group so if I screwed this up sorry. You can flame me. I come from DOS-land, have worked in it about a decade. I am not a specialist on DJGPP but if I understand what the non-interlaced means it is the way that the video card stores and retrieves information for the user. In non-interlaced mode all memory locations are stored contiguously straight through. In interlaced ever other screen line is contigous. In other words if you have a video buffer 64K in size the first 32K contains every odd numbered line, and the second 32K is every even numbered line. Or vice versa. I don't have a text handy, but I think that CGA used that approach. In case you think that this is stupid, it is now. Back then it was to enable slow cards and monitors to only refresh half the screen at refresh. If you are using someone elses graphics library you probably don't care whether it is interlaced or not. If you are writing your own library at the low level, you had better be ready to account for it. Hope I helped. "Never attribute to malice that which can be more easily explained by stupidity." - Hanlon's Razor