GUIDE TO USING GDB TO DEBUG X86 ASSEMBLY
 
Step 1. Add a nop as the first instruction after _start or main.
      _start:
      main:    nop  # add a nop so you can check things first 
 
Step 2. Assemble and link then load the progrom into gdb:
       $ make lab08
       $ gdb ./lab08
       (gdb) set language asm
       (gdb) break *_start+1    # set breakpoint right at the nop
       (gdb) si                 # step one instruction 
       (gdb) disassemble $pc    # display code starting a program counter
       (gdb) info registers
       (gdb) p/d $ecx           # display value as a decimal number in reg ecx
       (gdb) x/5i $pc           # examine 5 instructions past program counter 
       (gdb) cont
       (gdb) ret                # return from another function
       (gdb) exit

Using the debugger will help you understand why your code is not working as it 
should as well as trace your code's execution.