title: pop Instruction not supported in 64-bit mode using NASM?
body: <p>I'm working on a more indepth hello world using NASM <a href="http://www.cin.ufpe.br/~if817/arquivos/asmtut/quickstart.html" rel="noreferrer">following this tutorial</a> (section 4). This tutorial essentially teaches you how to handle command line input.
  <br>This is the snippet of the code in question:</p>
  
  <pre><code>section .text
          global _start
  
  _start:
          pop     ebx     ; arg count
          pop     ebx     ; arg[0] the program name
          pop     ebx     ; arg[1-n] the remainder of the args
                          ; must each be indiviually popped
  </code></pre>
  
  <p>The code errors out during compilation with <code>error: instruction not supported in 64-bit mode</code> referring to the 3 pop instructions above. <a href="http://cs.nyu.edu/courses/fall02/V22.0201-001/nasm_doc_html/nasmdocb.html#section-B.4.244" rel="noreferrer">Upon viewing the docs</a> it seems that this code only works for 32-bit systems. </p>
  
  <p>Is there a 64-bit <code>pop</code> instruction? Does anyone have a 64 bit tutorial using <code>pop</code> that I can look at?</p>