Sorry for all these asm questions, I just learned of a method in assembly language where you can print strings to the display by moveing them byte by byte into video memory at location 0B800h, I am learning this at http://www.xs4all.nl/~smit/asm02001.htm
It mentions 80x25 text mode, and in that mode, 4000 bytes of video memory at location B800:0000 can be used, I wrote my own program afterreading the example. If i start MS-DOS and move to the directory where my program resides, and I assemble and link with TASM and TLINK. No problems assembling or linking, I then type the name of the program and hit enter, it prints a blank line to the screen. So I figured maybe B800 is the wrong memory location, I pondered and played with my code for about a hour, still blank lines, I then tryed to asemble their example, and still blank lines, I I went back to the tutorial, I read about the video mode and figured maybe dos dont use that mode, then for some strange reason I decided to open windows explorer, and find my program and double click it, WOW it worked! so it must be something to do with the video mode, I then found theis site http://www.geocities.com/SiliconVall...odeSelect.html
I read the entire page, it apears there are difernt video modes, and i was useing 80x24 text mode.
My question is how come my program will work by double clicking the Icon, yet if I try to launch it from DOS all i get is a blank line???
P.S. If you really want to write 16 bit search for "draeden assembly"
they helped me tons
July 15th, 2002, 08:04 PM
Thank you for the link, I will check it out, however I am still going to learn 16 bit first before 32bit, as this is what I did with C, I learned how to make Dos apps in C, then moved on to makeing Win32 aps. So much to learn in so little time. I will soon learn how to incorporate asm code in C, so that I can write parts of my code in C, and parts in asm. As my goal is to make an operating system from scratch. 10X for the sugestions, I will definately check that link out soon.
July 15th, 2002, 08:10 PM
Sorry for the digression, but have you taken an OS class? Writing an operating system sounds a lot easier that it is. Setting up all the processes to work properly's quite a bit of work. I had dreams of writing an OS for a research project my freshman year of college (I was bored and my professors saw potential in me), but gave up after talking with the OS instructor. I ended up making a compiler instead, which was still challenging, but dramatically more easier, plus, I had the opportunity to play around with some assembly for that as well. If you want to incorporate assembly in C or C++, I suggest you start small... don't aim for an OS on your first try... I don't think you'll be happy with the results.
July 16th, 2002, 12:06 AM
A DOS session is controlled by a PIF ie.DOSPRMPT.PIF etc.
This is accessible by right clicking on a dos executable
or its icon.
I suspect that there is some difference in the PIF
for your dos prompt compared to the one for
double clicking the dos executable The PIF controls
several parameters of the dos session, such as
whether it runs full screen or windowed, and whether
the dos session closes when the program terminates,
memory usage etc. etc.
Play with these settings and you will uncover the
mystery of why the program works in one circumstance
and not the other.
BTW, here's a snippet of code for video memory
MOV AX,B800 ;GET ADDRESS OF VIDEO MEMORY
MOV DS,AX ;INTO DS REGISTER
MOV CX,07D0 ;# OF CHARS TO FILL SCREEN
MOV BX,0000 ;OFFSET OF FIRST BYTE OF VID MEM
MOV BYTE PTR [BX],DB ;PUT CHAR #DB IN FIRST BYTE
MOV BYTE PTR [BX+01],01 ;PUT 01h IN 2nd BYTE (ATTRIBUTE)
ADD BX,+02 ;GO TO NEXT CHAR POSITION OF VID MEM
LOOP 010B ;LOOP # OF TIMES IN CX (7D0h)
INT 20 ;TERMINATE (AND RETURN TO DOS)
It is a debug script. copy and paste it to a file, like
then at the command prompt type DEBUG<NEWBLUE.TXT
and debug will assemble it into a COM file.
It should turn the screen blue.
July 19th, 2002, 12:23 AM
rcgreen, thanks so much for that info, it helps alot. Just the kind of info I was looking for. I have got a lot of learning to do. Yes I agree that OS development is a big chalenge, I have however programed in many difernt high level languages such as C, C++, a bit of python and some qbasic. I am egar to get heavy into the deeprer aspects of programing. I have been learning a lot of asm though the past week or so. Development will not start for at least another 2 or more years, as I have much to learn. However I will not give up :)
thanks for all your advice and suport.
July 19th, 2002, 12:39 AM
Good luck to you and your OS. I'm expecting it'll be FREE and OpenSource. :)