You can save yourself a lot of time by getting a good book or two.
Mastering Turbo Assembler by Tom Swan ISBN 0-672-48435-8
Advanced Assembly Language by S. Holzner ISBN 0-13-663014-6
    Both books are for assembly on the Intel 8086 family of processors
using DOS. It's good to learn in DOS and then attack the more complex
operating systems.
Assuming an Intel x86 CPU and DOS, to clear the screen :
   xor CX,CX    ;CX=0
   mov DX,184fh
   xor AL,AL   ;AL=0
   mov BH,07h
   mov AH,06h  ;BIOS initialize/scroll service
   int 10h     ;call BIOS screen services
to position the cursor
   mov DH,Ypos  ;put your 'Y' axis into DH
   mov DL,Xpos  ;put your 'X' axis into DL
   mov AH,02h   ;BIOS position cursor service
   xor BH,BH    ;BH=0 use page 0 of screen memory
   int 10h      ;call BIOS screen services
 Use this code at your own risk! I garantee nothing!
Always test new assembly code with your debug before using. You
don't want the code running wild on you and erasing stuff.
Good luck!
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