MPLab1 Addition

32-bit Binary Addition Step by Step

1. Specify the memory model for code, data, and stack segments

.model small 
.stack 100H 
.386          ; This specifies that the program will use instructions of the 80386 processor (32-bit instructions).

2. Define your data in the data section ( here you can define various data items: variables, constants, strings, arrays)

.data          ; .data directive indicates the beginning of data section 
data1 dd 00H          ; declares a double-world variable and initializes it to 0. 
num1 db 10,13,"Enter the first number: $" 
num2 db 10,13,"Enter the second number: $" 
sum db 10,13,"The sum is :$" 

3. Define your instruction in the code section (here you write the assembly instructions that perform computations, control program flow, and interact with data variables and memory)

.code        ; .code directive indicates the beginning of code section 
.startup     ;  the entry point of the program

MOV EBX, 00000000        ; Initialize EBX to 0; EBX will be used to store the sum.

; Display the "Enter the first number: " message using DOS interrupt 21h (AH=09h).
MOV AH,09
MOV DX,OFFSET num1
INT 21H

MOV ECX, 8         ; initialize ECX to 8, to read 8 characters

AGAIN: MOV AH, 01     ; Read a character from the input device using DOS interrupt 21h (AH=01h).  AGAIN is label for loop.
INT 21H
CMP AL, 'A'                   ; Check if the character is greater than or equal to 'A' 
JGE P1                          ; If greater than 'A', jump to P1
SUB AL,30H                  ; subtract 30H to convert it to a decimal digit.     
JMP P4
P1: SUB AL, 37H          ; subtract 37H to convert it to a decimal digit.   
P4: SHL EBX, 4            ; Shift the value in EBX left by 4 bits 
MOV AH,00                  
ADD EBX, EAX           
LOOP AGAIN           
MOV data1, EBX

The Assembly Program Structure

An assembly program is separated into three sections as follows:

.MODEL SMALL
.STACK 100h

.DATA
;data definition go here

.CODE
;instructions go here

Steps to run Assembly programs in TASM

• Edit the program using any editor(gedit, notepad, etc.) and save the assembly code with .asm extension (e.g myCode.asm) in the same directory where you installed TASM and TLINK .
• Run TASM myCode.asm - it will invoke Turbo Assembler (TASM) which reads the "myCode.asm" file, processes the assembly instructions, and generates an object file or a binary executable file.
• Run TLINK myCode.obj - it will invoke Turbo Linker which reads the "myCode.obj" file, processes any external symbols and references, and combines it with other object files or libraries if needed. The result of this process is an executable program that you can run on your computer.
• Run myCode.exe - Once the linking process is successful, you can run your program by typing its name.
• Run TD myCode.exe - Debug (if needed)