问题
Good day. I'm new in assembly language and I'm trying to print a colored "Hello World" in TASM. Here is my code so far. It just prints "hello world" without a color.
.model small
.stack 100h
.data
message db 13,10,"Hello World!$"
.code
main proc near
lea dx, message
mov ah, 09h
int 21h
mov ah,4ch
int 21h
main endp
I've read something like this
mov ah,9 ;Function 9: Write character and attribute at cursor position
mov al,'H' ;AL = character to display
mov bh,0 ;BH = page number
mov bl,02EH ;BL = attribute (yellow on green)
mov cx,1 ;CX = number of times to write character
int 10H ;Int 10H: Video (show the character)
in a forum but I can't incorporate it with my hello world. I'm confused why use that particular register and the like. Please help me. Thank you very much!
EDIT
.model small
.stack 100h
.data
hello db 'Hello World!',0
.code
main proc near
mov ax, @data
mov ds, ax
mov ax, 3
int 10h
mov si, 0 ; cl is the counter register, set it to
; zero (the first character in the string)
start: ; Beginning of loop
mov al, hello[si] ; Read the next byte from memory
cmp al, 0 ; Compare the byte to null (the terminator)
je endthis ; If the byte is null, jump out of the loop
mov ah, 09h
mov al, hello[si]
mov bh, 0
mov bl,02EH
mov cx,11
int 10H
add si, 1 ; Move to the next byte in the string
jmp start ; Loop
endthis:
mov ah, 4ch
int 21h
main endp
end main
回答1:
Assembly language, as any programming language, is a result of arbitrary design decisions. Sometimes there can be a reason why a specific register is used as a interrupt call input register (optimization), but many times not, and you just have to take the interface (here int 10h or int 21h) as granted.
Related to your problem with several exclamation marks !!!!!!!!!!! (I assume 11 exclamation marks), you have incorrect parameters in your int 10 interrupt call:
mov cx,11
According to Ralf Brown's Interrupt List, the parameters for mov ah,9, int 10h are the following:
INT 10 - VIDEO - WRITE CHARACTER AND ATTRIBUTE AT CURSOR POSITION
AH = 09h
AL = character to display
BH = page number (00h to number of pages - 1) (see #00010)
background color in 256-color graphics modes (ET4000)
BL = attribute (text mode) or color (graphics mode)
if bit 7 set in <256-color graphics mode, character is XOR'ed
onto screen
CX = number of times to write character
Return: nothing
Notes: all characters are displayed, including CR, LF, and BS
replication count in CX may produce an unpredictable result in graphics
modes if it is greater than the number of positions remaining in the
current row
With PhysTechSoft's PTS ROM-DOS the BH, BL, and CX values are ignored
on entry.
So, instead of mov cx,11, it should be mov cx,1.
And the second mov al, hello[si] is redundant, because hello[si] has already been loaded into al at that time with the previous identical instruction. This doesn't affect the functioning of the code, however.
Edit: Added info on how to set and read the cursor location using int 10h.
It seems that you also need to update the cursor location with mov ah,2, int 10h, using the following parameters:
INT 10 - VIDEO - SET CURSOR POSITION
AH = 02h
BH = page number
0-3 in modes 2&3
0-7 in modes 0&1
0 in graphics modes
DH = row (00h is top)
DL = column (00h is left)
Return: nothing
Possibly you may need need to read the current cursor position with mov ah,3, int 10h, using the following parameters:
INT 10 - VIDEO - GET CURSOR POSITION AND SIZE
AH = 03h
BH = page number
0-3 in modes 2&3
0-7 in modes 0&1
0 in graphics modes
Return: AX = 0000h (Phoenix BIOS)
CH = start scan line
CL = end scan line
DH = row (00h is top)
DL = column (00h is left)
Notes: a separate cursor is maintained for each of up to 8 display pages
many ROM BIOSes incorrectly return the default size for a color display
(start 06h, end 07h) when a monochrome display is attached
With PhysTechSoft's PTS ROM-DOS the BH value is ignored on entry.
回答2:
If you're programming in assembly for DOS you should familiarize yourself with some of the commonly used interrupts, like int 10h and int 21h. For each interrupt subfunction there's a corresponding set of parameters that you need to pass to it through one or more registers.
The interrupt used in the example code you pasted is "WRITE CHARACTER AND ATTRIBUTE AT CURSOR POSITION", and you can find its description here.
In order to display a string with color attributes you'll have to iterate over the string in a loop and invoke the interrupt for each character with the appropriate parameters.
回答3:
.model small
.data
msg1 10,13,"hellow $"
.code
.startup
mov ah,09h
int 21h
.exit
end
来源：https://stackoverflow.com/questions/15323639/colored-hello-world-in-tasm