8086 assembly language program to split the screen into two colors left green right blue 
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10 July 2021 | 
1519
Write an assembly language program to color the entire screen into two halves. upon running the program the left half of the screen will become green when the space bar key is pressed. when the space bar key is released the right side becomes blue. The program terminates when enter key is pressed.
8086 Assembly Language Program
.model tiny ; com program
.code ; code segment
org 100h ; code starts at offset 100h
main proc near
loopmain:
mov ah,00h ; function to Read character from keyboard
int 16h ; keyboard interrupt 16h, output stored in al
cmp al,0dh ; check if enter key is pressed
je exit
cmp al,20h ; check if space bar is pressed
jne loopmain
cmp leftright,0
je left
mov leftcolor,0
mov rightcolor,1
call splitscreen
mov leftright,0
jmp loopmain
left:
mov leftcolor,2
mov rightcolor,0
call splitscreen
inc leftright
jmp loopmain
exit:
mov ah,4ch ; function to terminate
mov al,00
int 21h ; Dos Interrupt
endp
splitscreen proc near
mov ax,0xb800h
mov es,ax
mov di,0 ; Make Destination Index point to B800:0000
mov cx,50
mov bx,0
loop1:
mov al,0xdbh
mov es:[di],al ; Write to Video
inc di
cmp bx,39d
jg right
mov dl,leftcolor
mov es:[di],dl
jmp next
right:
mov dl,rightcolor
mov es:[di],dl
cmp bx,79d
jl next:
mov bx,00h
jmp next2:
next:
inc bx
next2:
inc di ; Next Display Area
loop loop1
ret
endp
leftcolor db 0
rightcolor db 0
leftright db 0
end main
The program works by writing the character 0xdbh which is the full white block from the character table to the memory. Here we write directly to the video memory b800h. when you write to b800h the first is the character to write the second is the color code of the character. Try this sample code
.model tiny ; com program
.code ; code segment
org 100h ; code starts at offset 100h
main proc near
mov ax,0xb800h
mov es,ax
mov es:00,'A'
mov es:01,3
mov es:02,'B'
mov es:03,4
mov ah,4ch
mov al,00
int 21h
endp
end main
In the above sample code we are displaying only two characters A followed by B. We are doing this by directly writing to the video segment 0xb800h. offset 00 we are writing character A, then 01 we are writing the color of the character. followed by B and color or B. This is the same technique I am using in the above code.