00. Before Start, Must Read this.txt

1.Basic Structure:

.model small			//code size
.stack 100h				//stack size
.code
main proc
    ;your operations here
    
    exit:
    mov ah, 4ch
    int 21h
    main endp
end main


2. 
Another segment after the stack segment is: The data segment (.data)
We can define any value (integer or string) in this segment.

.data
STARS db 0ah,0dh,'**********$' //0ah and 0ds for newline and carriage return. Dollar sign is mandatory for string
msg1 db 3  				 // variable name -> variable size -> value
msg db ? 				 //taking input from the users in the msg variable.

//And in main procedure, the data segment should be initialized.

main proc
mov ax,@data			//initialize ds
mov ds, ax

to print a string:

mov ah, 9 ; prepare to display
lea dx, STARS                 //
int 21h ;   display for once, it can be displayed several times by interrupting several times.


3. to print a new line:

mov ah, 2
mov dl, 10                    //newline
int 21h				//execution
mov dl, 13  			//carriage return
int 21h


4. 
Integer value input:
mov ah, 1   			// input done in (al) as usual
int 21h
mov bl, al				// save the value in bl register

another
mov ah, 1				// input done
int 21h				
mov bh, al				// save in bh. because in first input is in bl

5.
Print integer

mov ah, 2
int 21h
mov dl, bl				// output by dl
int 21h

another

mov ah, 2
int 21h
mov dl, bh
int 21h

6.
Pre-defined integer value print 
first, it should be searched from ascii table by adding 48
then print
mov ah, 2
add msg1, 48
mov dl, msg1
int 21h


7.
input msg variable

mov ah, 1
int 21h
mov msg1, al

Output:
mov ah, 2
mov dl, msg
int 21h


8.
Some info:

mov ah, 1  =>  single key input
mov ah, 2  => single char output
mov ah, 9  => char string output


9.
Add 2 numbers

add bl, bh
sub bl, 48
display

10.
Subtract 2 numbers

sub bl, bh
add bl, 48
display


11.
Upper to Lower case

A -> a    = sub 32
a -> A    = add 32