Append in file in Assembly

Following is the program to append in a file in Assembly language.

TITLE Append in file in Assembly Language
.model small
.stack

.data
file db "myfile.txt",0
msg db "This is a program to append in file in Assembly language.",'$'

.code
start:
main proc
mov ax,@data
mov ds,ax

;load file handler
mov dx,offset file
mov al,1
mov ah,3dh
int 21h

;Appending File
mov bx,ax
mov cx,0
mov ah,42h
mov al,02h
int 21h

;Writing File
mov cx,lengthof msg; should have been 1 less than length of msg.
mov dx,offset msg
mov ah,40h
int 21h

;close file
mov ah,3eh
int 21h

;exit
mov ax,4c00h
int 21h
main endp
end start
end

Read Character from Screen in Assembly Language

Program to read character from console screen in assembly language.

Move cursor in Assembly Language

How to move the cursor in Assembly Language?

Solution:

Example Code:

TITLE READ WHOLE SCREEN AND COPY CONTENT INTO SAVEBUFF
.model small
.stack
.data
hi db "Hi",'$'


.code
print macro string
mov ax,0900h
mov dx,0
mov dx,offset string
int 21h
endm
;-------------------------------------------------------------------------------------------------
start:
main proc
mov ax,@data
mov ds,ax

;move cursor from where copy data will start from screen into saveBuff
mov ax,0200h
mov dx,0200h; move cursor to 3rd row of 0th column
mov bx,0; video page = 0
int 10h

print hi

mov ax,4c00h
int 21h
main endp
end start
end

Write to file in Assembly Lanugage

.model small
.stack
.data
buffer db "I'm writing.",'$'
file db "myfile.txt",0


.code
mov ax,@data
mov ds,ax
 
mov dx, offset file
;mov al,0            ;Open file (read-Only)
mov al,1            ; Write only
;mov al,2            ; Read & Write
mov ah,3dh           ; Load File handler and store in ax
int 21h

mov cx,10            ; no. of bytes to be written. I want only first 10 bytes to be written in my already created file
mov bx,ax            ; Move file Handler to bx
mov dx,offset buffer ; load offset of string which is to be written to file
mov ah,40h
int 21h

mov ah,4ch
int 21h
end

Read from file Assembly Language

.model small
.stack
.data
buffer db 5000 dup("$")
file db "myfile.txt",0


.code
mov ax,@data
mov ds,ax
 
mov dx, offset file
mov al,0            ;Open file (read-Only)
;mov al,1            ; Write only
;mov al,2            ; Read & Write
mov ah,3dh           ; Load File handler and store in ax
int 21h

mov bx,ax            ; Move file Handler to bx
mov dx,offset buffer
mov ah,3fh
int 21h

mov ah,9h
int 21h

mov ah,4ch
int 21h
end

3fh not working Assembly Language

Problem: 3fh not working in Assembly Language

Solution: Don't do mov cx,0 before calling interrupt for input.

Displaying 2 digit number Assembly

TITLE Displaying 2 digit number in Assembly
.model small
.stack
.data

.code
mov ax,2579; 2579 will be displayed
mov cx,0
mov bx,10

loop1:
cmp ax,0
je next1
mov dx,0
div bx
push dx
inc cx
jmp loop1

next1:
mov ah,2h
loop2:
pop dx
add dx,48
int 21h
loop loop2

;exit:
mov ax,0
mov ah,4ch
int 21h
end