.data # switch to data segment
dest: # define the destination string, preinitialize as individual bytes
  .byte 'a', 'b', 'c', ' ', 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 14, 15
src:  # define the source string, preinitialize as a null-terminated string
  .asciz "0123456789"

.text
.global _start
_start:
  # preinitialize stuff
  movl  $dest, %eax # eax is p in the pseudocode
  movl  $src,  %ebx # ebx is q in the pseudocode
  movl  $4, %ecx # ecx is x in the pseudocode

  # I suggest that you use edx as i for simplicity

  #*******************
  # put your code here
  #*******************

  # at this point, dest should read as 'abc 0123'

  movl  $1, %eax # request program termination
  movl  $0, %ebx # with an exit code of 0
  int   $0x80