title: Can't call `putchar` in assembly
body: <p>I am trying to use the <code>putchar</code> function from the C standard library. It seems pretty straightforward--you pass in an int, and it writes the character to stdout. However, when I compile and run this program, nothing happens.</p>
  
  <pre><code>    # This doesn't work:
      .section .text
      .globl _start
  
  _start:
      mov $0x41, %dil
      call putchar
  
      mov $60, %rax
      syscall
  </code></pre>