Practical Assignment

Copy the assembly language program below to your H drive. Then assemble, link and run it as described in the next section


; Program: TEST.ASM

; AL Program to display the letter X on the screen
        .model small
        .stack 256
        mov dl, 'X'
        mov ah, 2h
        int 21h
; All programs use the following 3 lines to terminate
        mov ax, 4c00h
        int 21h
        end start


Assembling and Running Assembly Language Programs

An assembly language program must be assembled and linked before it can be executed.

The assembler produces an object file (extension .OBJ). This file is taken by the linker and an executable program (extension .EXE) is produced, assuming there were no errors in the program.

We use the MASM assembler and the LINK linker. These are available on NAL under Programming: “MASM files v5.0”.


When you choose MASM and click on it, NAL will install both MASM and LINK in your home directory in a folder called MASM. You only need to do this ONCE.

The full name for this folder is H:\MASM

Create a program called TEST.ASM by copying the program text above and using Notepad (or Edit) save the file is in your home directory on the H:\ drive in the MASM folder. The file name will be: H:\MASM\TEST.ASM.

When saving the file with Notepad, you MUST save it with the “File Type” set to “All Files”.

You should now select the MS-DOS Prompt (Command PROMPT) from the Start button menu (sometimes under Programs option).


You now get an MS-DOS window where you have to enter commands by typing the name of the command you wish to use. Common commands are

TYPE filename to display the file filename on the screen;

DEL filename to delete the file called filename

COPY filename newname: to make a copy of filename called newname

To view your program, you may use the TYPE program:

H:\> type H:TEST.ASM


Running your program


First: Assemble it using MASM

H:\> masm test

Microsoft (R) Macro Assembler Version 5.10

Copyright (C) Microsoft Corp 1981, 1988. All rights reserved.

Object filename [H:TEST.OBJ]:                                                   Press Return

Source listing [NUL.LST]:                                                                 Press Return

Cross-reference [NUL.CRF]:                                                                    Press Return

48928 + 432619 Bytes symbol space free

0 Warning Errors

0 Severe Errors

Note: The file test.asm MUST be in the same folder as MASM for the above to work.


Secondly: Link it using Link

Having successfully assembled your program, as above, you now link it in a similar fashion:


H:\> link test

Microsoft (R) Overlay Linker Version 3.64

Copyright (C) Microsoft Corp 1983-1988. All rights reserved.

Run File [H:TEST.EXE]:                                                                    Press Return

List File [NUL.MAP]:                                                                               Press Return

Libraries [.LIB]:                                                     Press Return


Note: The file test.obj MUST be in the same folder as LINK for the above to work.


Finally, run it by entering the program name

To run your program, simply enter its name:

H:\> test

In the event of errors, you must edit your program and correct the errors. Then you repeat the above steps to assemble and link your program, before running it.

Similarly, if you modify your program, you must assemble and link it before running it again.


Problems with Copying Programs from Web Page

Sometimes when you copy a program from a web page, the quotes character (“) gets changed when you copy it to a DOS file. If this happens MASM will report an error. To correct this error, simply edit the program and enter the quote (“) character again.