GDB: why does memory mapping change after run?

Why does memory mapping change in GDB after run?
For instance, the main function below is initially at 0x00000560 and then after run it is at 0x80000560.

Is it possible to run/configure gdb the way it shows real mapping from the beginning?

Reading symbols from prog...(no debugging symbols found)...done.
(gdb) disas main
Dump of assembler code for function main:
   0x00000560 : push   %ebp
   0x00000561 : mov    %esp,%ebp
   0x00000563 : sub    $0x10,%esp
   0x00000566 : call   0x580 
   0x0000056b :    add    $0x1a95,%eax
   0x00000570 :    movl   $0x0,-0x4(%ebp)
   0x00000577 :    addl   $0x1,-0x4(%ebp)
   0x0000057b :    mov    -0x4(%ebp),%eax
   0x0000057e :    leave  
   0x0000057f :    ret    
End of assembler dump.
(gdb) run
Starting program: /home/mike/gdb/prog 
[Inferior 1 (process 9607) exited with code 01]
(gdb) disas main
Dump of assembler code for function main:
   0x80000560 : push   %ebp
   0x80000561 : mov    %esp,%ebp
   0x80000563 : sub    $0x10,%esp
   0x80000566 : call   0x80000580 
   0x8000056b :    add    $0x1a95,%eax
   0x80000570 :    movl   $0x0,-0x4(%ebp)
   0x80000577 :    addl   $0x1,-0x4(%ebp)
   0x8000057b :    mov    -0x4(%ebp),%eax
   0x8000057e :    leave  
   0x8000057f :    ret    
End of assembler dump.

For instance, the main function below is initially at 0x00000560 and then after run it is at 0x80000

You have a position-independent executable (really just a special kind of shared library, linked with -pie flag). It is relocated to a random address before it starts executing.

Note that GDB will usually try to disable address randomization, so the random address will not actually vary from run to run under GDB. However, it will vary when the program is run outside of GDB, or if you use (gdb) set disable-randomization off.