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Ivan Botero
Asked: 2020-04-02 07:04:20 +0800 CST 2020-04-02 07:04:20 +0800 CST

Problem printing message in debug - Windows

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I am doing an assembly programming practice, on the Windows debug tool for 32 bits.

The proposed exercise is as follows:

Starting at memory location 012F design an algorithm that displays the following stream of characters "This is my first program in DEBUG"

We have been given an example of how to print the typical "Hello World" in assembler.

functional example

Following this example, I then proceeded to write my version depending on the proposed exercise:

-a
   jmp 120

-e 0102 "Este es mi primer programa en debug" 0a 0d "$"
-a 120
   mov ah,09
   mov dx,0102
   int 21
   int 20

All this code, I wrote it, based on the working example. The only thing I have changed is the text.

But when executing the program (that is, executing the -g instruction).

I get the following result:

Failed Example

I do not understand where the problem is, I have reviewed the notes, regarding the instructions, but I do not understand what has failed.

My question is:

What is the error that I have made, which leads me to obtain said erroneous result?

windows

1 Answers

  1. Best Answer

    Change your code to the following:

    -a
   jmp 130

-e 0102 "Este es mi primer programa en debug" 0a 0d "$"
-a 130
   mov ah,09
   mov dx,0102
   int 21
   int 20

-g

    I'm not very good with assembler, but what I can notice is that you stringare located at position 0102and your application starts at 0120.

    Now, being

    "This is my first debug program"

    longer than

    "Hello World"

    needs more available positions to be copied. Therefore, when the application starts writing at position 0120, it is overwriting the stringand when it tries to print it does not find the end of the string "$".

    So what we're doing with the location 0130is starting the app a little further away so that the string has enough space to be copied.

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