How To Print A Single Character in 8086 Assembly Language

 If you are getting started with 8086 assembly programming, you might encounter the elementary and very beginning program of your life, which is “how to print text in 8086 assembly language”. However, in most cases, the next step is to print a single character in the 8086 assembly language.

In an 8086 assembly language computer always works with registers of the microprocessor. in intel’s 8086 microprocessor, there are four basic general-purpose or data registers i.e.

Accumulator Register (AX)

Base Register (BX)

Counter Register (CX)

Data Register (DX)

Above mentioned registers are 16bit registers which means they consist of two bytes. These registers are further broken into ‘high byte’ and ‘low byte'. We can use them for any purpose we want. Look at the table below.

There are other types of registers as well, but for now, we will stick to them.

Now that we have an overview of Data registers, we can now write a simple assembly language program that prints single character output. 

First, we write our basic program template, which does nothing but is very important and will always be used in each assembly program.

TITLE SINGLE_CHARACTER_PRINTING

.MODEL SMALL

.STACK 100H

.DATA

;;THIS IS DATA SECTION

.CODE   

;THIS IS CODE SECTION

    MAIN:

        MOV AX, @DATA

        MOV DS, AX

        

        

            

        

        

        MOV AH, 04CH

        INT 21H

   END MAIN

If you don’t understand or want to understand more basics, you can follow this link for the instructions used in this program.

In the 8086 assembly language, a single character means one byte. Let’s say we want to print ‘A’ first, we need to move it to the data register, which is DX, and ‘A’ is one byte so that we will place it in the DL register. If you are confused, remember that if you want to print a single character, always move it to the ‘DL’ register.

MOV DL, ‘A’

MOV AH, 02H

INT 21H

Just add three lines in the above code, and you will see the output of the program. If you don't understand MOV AH, 02H and INT 21H, just go with it as at this point there is no need to get stuck to it. Just remember we write these three statements to display a single character. You just need to replace the ‘A’ in DL if you want to print something else.

Following is the complete code of above program

TITLE SINGLE_CHARACTER_PRINTING

.MODEL SMALL

.STACK 100H

.DATA

;;THIS IS DATA SECTION

.CODE   

;THIS IS CODE SECTION

    MAIN:

        MOV AX, @DATA

        MOV DS, AX

        

        MOV DL, 'A'

        MOV AH, 02H

        INT 21H

                        

        MOV AH, 04CH

        INT 21H

   END MAIN

You should see output of the program as 'A'

If you have any question or trouble you can always choose to click Ask for Help section mentioned above.

How To Print A Single Character in 8086 Assembly Language

How To Print Text In 8086 Assembly : Code Explained

8086 Program To Print Text In Assembly

How To Print Text In 8086 Assembly : Code Explained

This program prints simple text on screen in 8086 assembly language. Click to download the code

Printing a text in assembly language is very easy.

In assembly language we need to build a logic and then write a program. In this program we only need to print a simple message for which we have written this code.

1.      First we write the title of program so that we can understand the purpose of program

   TITLE TEXT_MESSAGE

2.      Then we define the model, model is the part of program which tells assembler which model we need to use for our program. In this program we are using SMALL,  but there are many like TINY, SMALL and LARGE

   .MODEL SMALL

3.      Then we define the stack of program. STACK usually tells assembler that how much bytes we need to use for our DATA SEGMENT (explained later). In this program we have used 100 bytes in hexadecimal

   .STACK 100H

4.      Now comes the DATA SEGMENT, which, we define as .DATA. in DATA SEGMENT  we store our variables and temporary data. For example our temporary bytes. In this program we have stored an array of characters containing our message.

That’s how you define a array of characters (string) in assembly.

NAME	TYPE	“MESSAGES$”
MSG	DB	0AH, 0DH, "TEXT MESSAGE$"

MSG is the name of message you can have any name, DB is DEFINE BYTE (will be explained further in variables section) and then our text message. You notice 0AH and 0DH these bytes are for carriage return and line feed, now the message which is in quotes, be careful for dollar sign ($), which is string terminator, do not forget to add it after every message.

5.      After setting up DATA SEGMENT, CODE SEGMENT starts, which tells assembler that our program has been started. We define CODE SEGMENT same as we defined DATA SEGMENT.

.CODE

In the code segment first we define a label from which our program starts, in this program we have defined MAIN: with colon. Then we move starting address of DATA SEGMENT by using AX register in to DS register (will be explained later programs). First move address to AX register then mov it back to DS register.

MOV AX, @DATA

MOV DS, AX

6.      To print the message we need to move its address to DX register there are two way to do it but we will use OFFSET command to do it. After moving address to DX register we store 09H byte in AH register to tell assembler that we want to print a string. Now we invoke interrupt service routine by using INT 21H

MOV DX, OFFSET MSG

MOV AH, 09H

INT 21H

      

7.      Now that we have completed the task of string printing we need to tell assembler that where to end the program for this we simply define another label name EXIT: with colon and move 4CH byte in AH register and invoke INT 21H after this we use END MAIN (without colon)

EXIT:    

        MOV AH, 04CH

        INT 21H

END MAIN

Here is the complete program.

How To Print A Single Character in 8086 Assembly Language

How To Print Text In 8086 Assembly : Code Explained

8086 Program To Print Text In Assembly

8086 Program To Print Text In Assembly

for code explanation please follow how to print text in 8086 assembly code. Thanks

; CODE BEGINS

TITLE TEXT_MESSAGE 
.MODEL SMALL 
.STACK 100H 
.DATA 
 
    MSG DB 0AH, 0DH, "TEXT MESSAGE$" 
.CODE 
    MAIN: 
        MOV AX, @DATA 
        MOV DS, AX 
         
        MOV DX, OFFSET MSG 
        MOV AH, 09H 
        INT 21H        
         
  ;     LEA DX, MSG 
  ;     MOV AH, 09H 
  ;     INT 21H 
         
         
         
         
         
    EXIT:     
        MOV AH, 04CH 
        INT 21H 
    END MAIN 

; CODE ENDS

Following is the output of the program

How To Print A Single Character in 8086 Assembly Language

How To Print Text In 8086 Assembly : Code Explained

8086 Program To Print Text In Assembly