#Whitespace, 59 bytes

Visible representation

NSSNSSSTSSSSSNSNSSNSSNSTNTSTTTTSSTNTTSNSNSTSSSNSSSNTNSSNSNN

What it does:

For every character it reads it prints a space, except when it's a space, then it prints a @.

Disassembly:

loop:
    push 32
     dup
      dup
       dup
        ichr
       get
       sub
      jn not_32
     dup
      add
not_32:
     pchr
    jmp loop

Whitespace, 59 bytes

Visible representation

NSSNSSSTSSSSSNSNSSNSSNSTNTSTTTTSSTNTTSNSNSTSSSNSSSNTNSSNSNN

What it does:

For every character it reads it prints a space, except when it's a space, then it prints a @.

Disassembly:

loop:
    push 32
     dup
      dup
       dup
        ichr
       get
       sub
      jn not_32
     dup
      add
not_32:
     pchr
    jmp loop