title: Parallel Port Interfacing in Assembly Language
body: <p>Hi I am having problem in interfacing Parallel port using Assembly Language and TASM for assembly.</p>
  
  <p>Here is the sample source code:</p>
  
  <pre><code>.model small
  .stack
  .data
  .code
  
  main:           
      mov dx, 378h
      mov al, 00001000b 
      out dx, al ; output
  
      mov ah, 4ch
      int 21h
  
  end main 
  </code></pre>
  
  <p>The problem is the out command doesn't work or change the status of the parallel port. I have an LED circuit to test the output of the parallel port and it's not working. I have tried other program available in the net to check the status of the parallel port and I confirmed that the status of the port is not changing.</p>
  
  <p>Do I have to do something to make this work like enabling debug mode in kernel or something like that? Thank you!</p>